Power, heat flow

The method for setting temperature values ​​is the temperature scale. Several temperature scales are known.

• Kelvin scale(named after the English physicist W. Thomson, Lord Kelvin).
  Unit designation: K(not “degree Kelvin” and not °K).
  1 K = 1/273.16 - part of the thermodynamic temperature of the triple point of water, corresponding to the thermodynamic equilibrium of a system consisting of ice, water and steam.
• Celsius(named after the Swedish astronomer and physicist A. Celsius).
  Unit designation: °C .
  In this scale, the melting temperature of ice at normal pressure is taken to be 0°C, and the boiling point of water is 100°C.
  The Kelvin and Celsius scales are related by the equation: t (°C) = T (K) - 273.15.
• Fahrenheit(D. G. Fahrenheit - German physicist).
  Unit symbol: °F. Widely used, particularly in the USA.
  The Fahrenheit scale and the Celsius scale are related: t (°F) = 1.8 · t (°C) + 32°C. In absolute value, 1 (°F) = 1 (°C).
• Reaumur scale(named after the French physicist R.A. Reaumur).
  Designation: °R and °r.
  This scale is almost out of use.
  Relation to degrees Celsius: t (°R) = 0.8 t (°C).
• Rankin Scale (Rankine)- named after the Scottish engineer and physicist W. J. Rankin.
  Designation: °R (sometimes: °Rank).
  The scale is also used in the USA.
  Temperature on the Rankine scale is related to temperature on the Kelvin scale: t (°R) = 9/5 · T (K).

Basic temperature indicators in units of measurement of different scales:

The SI unit of measurement is meter (m).

• Non-system unit: Angstrom (Å). 1Å = 1·10-10 m.
• Inch(from Dutch duim - thumb); inch; in; ´´; 1´ = 25.4 mm.
• Hand(English hand - hand); 1 hand = 101.6 mm.
• Link(English link - link); 1 li = 201.168 mm.
• Span(English span - span, scope); 1 span = 228.6 mm.
• Foot(English foot - leg, feet - feet); 1 ft = 304.8 mm.
• Yard(English yard - yard, corral); 1 yd = 914.4 mm.
• Fat, face(English fathom - measure of length (= 6 ft), or measure of volume of wood (= 216 ft 3), or mountain measure of area (= 36 ft 2), or fathom (Ft)); fath or fth or Ft or ƒfm; 1 Ft = 1.8288 m.
• Cheyne(English chain - chain); 1 ch = 66 ft = 22 yd = = 20.117 m.
• Furlong(eng. furlong) - 1 fur = 220 yd = 1/8 mile.
• mile(English mile; international). 1 ml (mi, MI) = 5280 ft = 1760 yd = 1609.344 m.

The SI unit is m2.

• Square foot; 1 ft 2 (also sq ft) = 929.03 cm 2.
• Square inch; 1 in 2 (sq in) = 645.16 mm 2.
• Square fathom (fesom); 1 fath 2 (ft 2; Ft 2; sq Ft) = 3.34451 m 2.
• Square Yard; 1 yd 2 (sq yd)= 0.836127 m 2 .

Sq (square) - square.

The SI unit is m3.

• Cubic foot; 1 ft 3 (also cu ft) = 28.3169 dm 3.
• Cubic Fathom; 1 fath 3 (fth 3; Ft 3; cu Ft) = 6.11644 m 3.
• Cubic Yard; 1 yd 3 (cu yd) = 0.764555 m 3.
• Cubic inch; 1 in 3 (cu in) = 16.3871 cm 3.
• Bushel (UK); 1 bu (uk, also UK) = 36.3687 dm 3.
• Bushel (USA); 1 bu (us, also US) = 35.2391 dm 3.
• Gallon (UK); 1 gal (uk, also UK) = 4.54609 dm 3.
• Gallon liquid (USA); 1 gal (us, also US) = 3.78541 dm 3.
• Gallon dry (USA); 1 gal dry (us, also US) = 4.40488 dm 3.
• Jill (gill); 1 gi = 0.12 l (US), 0.14 l (UK).
• Barrel (USA); 1bbl = 0.16 m3.

UK - United Kingdom- United Kingdom (UK); US - United Stats (USA).

Specific volume

The SI unit of measurement is m 3 /kg.

• ft 3/lb; 1 ft3 / lb = 62.428 dm 3 / kg .

The SI unit of measurement is kg.

• Pound (trading) (English libra, pound - weighing, pound); 1 lb = 453.592 g; lbs - pounds. In the system of old Russian measures 1 lb = 409.512 g.
• Gran (English grain - grain, grain, grain); 1 gr = 64.799 mg.
• Stone (eng. stone - stone); 1 st = 14 lb = 6.350 kg.

Density, incl. bulk

The SI unit of measurement is kg/m3.

• lb/ft 3 ; 1 lb/ft 3 = 16.0185 kg/m 3.

Linear density

The SI unit is kg/m.

• lb/ft; 1 lb/ft = 1.48816 kg/m
• Pound/Yard; 1 lb / yd = 0.496055 kg/m

Surface density

The SI unit is kg/m2.

• lb/ft 2 ; 1 lb / ft 2 (also lb / sq ft - pound per square foot) = 4.88249 kg/m2.

Linear speed

The SI unit is m/s.

• ft/h; 1 ft/h = 0.3048 m/h.
• ft/s; 1 ft/s = 0.3048 m/s.

The SI unit is m/s2.

• ft/s 2 ; 1 ft/s2 = 0.3048 m/s2.

Mass flow

The SI unit is kg/s.

• lb/h; 1 lb/h = 0.453592 kg/h.
• lb/s; 1 lb/s = 0.453592 kg/s.

Volume flow

The SI unit of measurement is m 3 /s.

• ft 3 /min; 1 ft 3 / min = 28.3168 dm 3 / min.
• Yard 3/min; 1 yd 3 / min = 0.764555 dm 3 / min.
• Gpm; 1 gal/min (also GPM - gallon per min) = 3.78541 dm 3 /min.

Specific volume flow

• GPM/(sq·ft) - gallon (G) per (P) minute (M)/(square (sq) · foot (ft)) - gallons per minute per square foot;
  1 GPM/(sq ft) = 2445 l/(m 2 h) 1 l/(m 2 h) = 10 -3 m/h.
• gpd - gallons per day - gallons per day (day); 1 gpd = 0.1577 dm 3 /h.
• gpm - gallons per minute - gallons per minute; 1 gpm = 0.0026 dm 3 /min.
• gps - gallons per second - gallons per second; 1 gps = 438 10 -6 dm 3 /s.

Consumption of sorbate (for example, Cl 2) when filtering through a layer of sorbent (for example, activated carbon)

• Gals/cu ft (gal/ft 3) - gallons/cubic foot (gallons per cubic foot); 1 Gals/cu ft = 0.13365 dm 3 per 1 dm 3 of sorbent.

The SI unit of measurement is N.

• Pound-force; 1 lbf - 4.44822 N. (An analogue of the name of the unit of measurement: kilogram-force, kgf. 1 kgf = = 9.80665 N (exact). 1 lbf = 0.453592 (kg) 9.80665 N = = 4 .44822 N 1N=1 kg m/s 2
• Poundal (English: poundal); 1 pdl = 0.138255 N. (Poundall is the force that gives a mass of one pound an acceleration of 1 ft/s 2, lb ft/ s 2.)

Specific gravity

The SI unit of measurement is N/m 3 .

• lbf/ft 3 ; 1 lbf/ft 3 = 157.087 N/m 3.
• Poundal/ft 3 ; 1 pdl/ft 3 = 4.87985 N/m 3.

SI unit of measurement - Pa, multiple units: MPa, kPa.

In their work, specialists continue to use outdated, canceled or previously optionally accepted units of pressure measurement: kgf/cm 2; bar; atm. (physical atmosphere); at(technical atmosphere); ata; ati; m water Art.; mmHg st; torr.

The following concepts are used: “ absolute pressure", "overpressure". There are errors when converting some pressure units into Pa and its multiples. It should be taken into account that 1 kgf/cm 2 is equal to 98066.5 Pa (exactly), that is, for small (up to approximately 14 kgf/cm 2) pressures with sufficient accuracy for work the following can be accepted: 1 Pa = 1 kg/(m s 2) = 1 N/m 2. 1 kgf/cm 2 ≈ 105 Pa = 0.1 MPa. But already at medium and high pressures: 24 kgf/cm 2 ≈ 23.5 105 Pa = 2.35 MPa; 40 kgf/cm2 ≈ 39 · 105 Pa = 3.9 MPa; 100 kgf/cm 2 ≈ 98 105 Pa = 9.8 MPa etc.

Ratios:

• 1 atm (physical) ≈ 101325 Pa ≈ 1.013 105 Pa ≈ ≈ 0.1 MPa.
• 1 at (technical) = 1 kgf/cm 2 = 980066.5 Pa ≈ ≈ 105 Pa ≈ 0.09806 MPa ≈ 0.1 MPa.
• 0.1 MPa ≈ 760 mm Hg. Art. ≈ 10 m water. Art. ≈ 1 bar.
• 1 Torr (tor) = 1 mm Hg. Art.
• lbf/in 2 ; 1 lbf/in 2 = 6.89476 kPa (see below: PSI).
• lbf/ft 2 ; 1 lbf/ft 2 = 47.8803 Pa.
• lbf/yd 2 ; 1 lbf/yd 2 = 5.32003 Pa.
• Poundal/ft 2 ; 1 pdl/ft 2 = 1.48816 Pa.
• Foot water column; 1 ft H 2 O = 2.98907 kPa.
• Inch of water column; 1 in H 2 O = 249.089 Pa.
• Inch of mercury; 1 in Hg = 3.38639 kPa.
• PSI (also psi) - pounds (P) per square (S) inch (I) - pounds per square inch; 1 PSI = 1 lbƒ/in 2 = 6.89476 kPa.

Sometimes in the literature you can find the designation of the pressure unit lb/in 2 - this unit takes into account not lbƒ (pound-force), but lb (pound-mass). Therefore, in numerical terms, 1 lb/ in 2 is slightly different from 1 lbf/ in 2, since when determining 1 lbƒ it is taken into account: g = 9.80665 m/s 2 (at the latitude of London). 1 lb/in 2 = 0.454592 kg/(2.54 cm) 2 = 0.07046 kg/cm 2 = 7.046 kPa. Calculation of 1 lbƒ - see above. 1 lbf/in 2 = 4.44822 N/(2.54 cm) 2 = 4.44822 kg m/ (2.54 0.01 m) 2 s 2 = 6894.754 kg/ (m s 2) = 6894.754 Pa ≈ 6.895 kPa.

For practical calculations we can assume: 1 lbf/in 2 ≈ 1 lb/in 2 ≈ 7 kPa. But, in fact, equality is illegal, just like 1 lbƒ = 1 lb, 1 kgf = 1 kg. PSIg (psig) - same as PSI, but indicates gauge pressure; PSIa (psia) - the same as PSI, but emphasizes: absolute pressure; a - absolute, g - gauge (measure, size).

Water pressure

The SI unit of measurement is m.

• Head in feet (feet-head); 1 ft hd = 0.3048 m

Pressure loss during filtration

• PSI/ft - pounds (P) per square (S) inch (I)/foot (ft) - pounds per square inch/foot; 1 PSI/ft = 22.62 kPa per 1 m of filter layer.

SI unit of measurement - Joule(named after the English physicist J.P. Joule).

• 1 J - mechanical work of force 1 N when moving a body over a distance of 1 m.
• Newton (N) is the SI unit of force and weight; 1 Н is equal to the force imparting to a body weighing 1 kg an acceleration of 1 m 2 /s in the direction of the force. 1 J = 1 N m.

In heating engineering, they continue to use the abolished unit of measurement of the amount of heat - calorie (cal).

• 1 J (J) = 0.23885 cal. 1 kJ = 0.2388 kcal.
• 1 lbf ft (lbf) = 1.35582 J.
• 1 pdl ft (poundal feet) = 42.1401 mJ.
• 1 Btu (British Heat Unit) = 1.05506 kJ (1 kJ = 0.2388 kcal).
• 1 Therm (British large calorie) = 1 10 -5 Btu.

POWER, HEAT FLOW

SI unit of measurement is Watt (W)- named after the English inventor J. Watt - mechanical power at which 1 J of work is performed in 1 s, or a heat flux equivalent to 1 W of mechanical power.

• 1 W (W) = 1 J/s = 0.859985 kcal/h (kcal / h).
• 1 lbf ft/s (lbf ft/s) = 1.33582 W.
• 1 lbf ft/min (lbf ft/min) = 22.597 mW.
• 1 lbf ft/h (lbf ft/h) = 376.616 µW.
• 1 pdl ft/s (poundal feet/s) = 42.1401 mW.
• 1 hp (British horsepower/s) = 745.7 W.
• 1 Btu/s (British Heat Unit/s) = 1055.06 W.
• 1 Btu/h (British Heat Unit/h) = 0.293067 W.

Surface heat flux density

The SI unit is W/m2.

• 1 W/m2 (W/m2) = 0.859985 kcal/(m2 h) (kcal/(m2 h)).
• 1 Btu/(ft 2 h) = 2.69 kcal/(m 2 h) = 3.1546 kW/m 2.

Dynamic viscosity (viscosity coefficient), η.

SI unit - Pa s. 1 Pa s = 1 N s/m2;
non-systemic unit - poise (P). 1 P = 1 dyne s/m 2 = 0.1 Pa s.

• Dina (dyn) - (from the Greek dynamic - strength). 1 dyne = 10 -5 N = 1 g cm/s 2 = 1.02 10 -6 kgf.
• 1 lbf h/ft 2 (lbf h/ft 2) = 172.369 kPa s.
• 1 lbf s / ft 2 (lbf s/ft 2) = 47.8803 Pa s.
• 1 pdl s / ft 2 (poundal-s/ft 2) = 1.48816 Pa s.
• 1 slug /(ft s) = 47.8803 Pa s. Slug (slug) is a technical unit of mass in the English system of measures.

Kinematic viscosity, ν.

Unit of measurement in SI - m 2 /s; The unit cm 2 /s is called “Stokes” (named after the English physicist and mathematician J. G. Stokes).

Kinematic and dynamic viscosity are related by the equality: ν = η / ρ, where ρ is density, g/cm 3 .

• 1 m 2 /s = Stokes / 104.
• 1 ft 2 /h (ft 2 /h) = 25.8064 mm 2 /s.
• 1 ft 2 /s (ft 2 /s) = 929.030 cm 2 /s.

The SI unit of magnetic field strength is A/m(Ammeter). Ampere (A) is the surname of the French physicist A.M. Ampere.

Previously, the Oersted unit (E) was used - named after the Danish physicist H.K. Oersted.
1 A/m (A/m, At/m) = 0.0125663 Oe (Oe)

The resistance to crushing and abrasion of mineral filter materials and, in general, of all minerals and rocks is indirectly determined using the Mohs scale (F. Mohs - German mineralogist).

In this scale, numbers in ascending order designate minerals arranged in such a way that each subsequent one is capable of leaving a scratch on the previous one. The extreme substances on the Mohs scale are talc (hardness unit 1, the softest) and diamond (10, the hardest).

• Hardness 1-2.5 (drawn with a fingernail): volskonkoite, vermiculite, halite, gypsum, glauconite, graphite, clay materials, pyrolusite, talc, etc.
• Hardness >2.5-4.5 (not drawn with a fingernail, but drawn with glass): anhydrite, aragonite, barite, glauconite, dolomite, calcite, magnesite, muscovite, siderite, chalcopyrite, chabazite, etc.
• Hardness >4.5-5.5 (not drawn with glass, but drawn with a steel knife): apatite, vernadite, nepheline, pyrolusite, chabazite, etc.
• Hardness >5.5-7.0 (not drawn with a steel knife, but drawn with quartz): vernadite, garnet, ilmenite, magnetite, pyrite, feldspars, etc.
• Hardness >7.0 (not marked with quartz): diamond, garnets, corundum, etc.

The hardness of minerals and rocks can also be determined using the Knoop scale (A. Knoop - German mineralogist). In this scale, values ​​are determined by the size of the imprint left on the mineral when a diamond pyramid is pressed into its sample under a certain load.

Ratios of indicators on the Mohs (M) and Knoop (K) scales:

SI unit of measurement - Bq(Becquerel, named after the French physicist A.A. Becquerel).

Bq (Bq) is a unit of activity of a nuclide in a radioactive source (isotope activity). 1 Bq is equal to the activity of a nuclide, at which one decay event occurs in 1 s.

Radioactivity concentration: Bq/m 3 or Bq/l.

Activity is the number of radioactive decays per unit time. The activity per unit mass is called specific.

• Curie (Ku, Ci, Cu) is a unit of activity of a nuclide in a radioactive source (isotope activity). 1 Ku is the activity of an isotope in which 3.7000 · 1010 decay events occur in 1 s. 1 Ku = 3.7000 · 1010 Bq.
• Rutherford (Рд, Rd) is an obsolete unit of activity of nuclides (isotopes) in radioactive sources, named after the English physicist E. Rutherford. 1 Rd = 1 106 Bq = 1/37000 Ci.

Radiation dose

Radiation dose is the energy of ionizing radiation absorbed by the irradiated substance and calculated per unit of its mass (absorbed dose). The dose accumulates over time of exposure. Dose rate ≡ Dose/time.

SI unit of absorbed dose - Gray (Gy, Gy). The extrasystemic unit is Rad, corresponding to the radiation energy of 100 erg absorbed by a substance weighing 1 g.

Erg (erg - from the Greek: ergon - work) is a unit of work and energy in the non-recommended GHS system.

• 1 erg = 10 -7 J = 1.02 10 -8 kgf m = 2.39 10 -8 cal = 2.78 10 -14 kW h.
• 1 rad = 10 -2 Gr.
• 1 rad (rad) = 100 erg/g = 0.01 Gy = 2.388 · 10 -6 cal/g = 10 -2 J/kg.

Kerma (abbreviated English: kinetic energy released in matter) - kinetic energy released in matter, measured in grays.

The equivalent dose is determined by comparing the nuclide radiation with X-ray radiation. The radiation quality factor (K) shows how many times the radiation hazard in the case of chronic human irradiation (in relatively small doses) for a given type of radiation is greater than in the case of x-ray radiation at the same absorbed dose. For X-ray and γ-radiation K = 1. For all other types of radiation K is established according to radiobiological data.

Deq = Dpogl · K.

SI unit of absorbed dose - 1 Sv(Sievert) = 1 J/kg = 102 rem.

• BER (rem, ri - until 1963 was defined as the biological equivalent of an x-ray) - a unit of equivalent dose of ionizing radiation.
• X-ray (P, R) - unit of measurement, exposure dose of X-ray and γ-radiation. 1 P = 2.58 10 -4 C/kg.
• Coulomb (C) is an SI unit, amount of electricity, electric charge. 1 rem = 0.01 J/kg.

Equivalent dose rate - Sv/s.

Permeability of porous media (including rocks and minerals)

Darcy (D) - named after the French engineer A. Darcy, darsy (D) · 1 D = 1.01972 µm 2.

1 D is the permeability of such a porous medium, when filtering through a sample with an area of ​​1 cm 2, a thickness of 1 cm and a pressure drop of 0.1 MPa, the flow rate of a liquid with a viscosity of 1 cP is equal to 1 cm 3 /s.

Sizes of particles, grains (granules) of filter materials according to SI and standards of other countries

In the USA, Canada, Great Britain, Japan, France and Germany, grain sizes are estimated in meshes (eng. mesh - hole, cell, network), that is, by the number (number) of holes per inch of the finest sieve through which they can pass grains And the effective grain diameter is the hole size in microns. IN last years The US and UK mesh systems are more commonly used.

The relationship between the units of measurement of grain sizes (granules) of filter materials according to SI and standards of other countries:

Mass fraction

Mass fraction shows what mass amount of a substance is contained in 100 parts by mass of a solution. Units of measurement: fractions of a unit; interest (%); ppm (‰); parts per million (ppm).

Solution concentration and solubility

The concentration of a solution must be distinguished from solubility - the concentration of a saturated solution, which is expressed by the mass amount of a substance in 100 parts by mass of a solvent (for example, g/100 g).

Volume concentration

Volume concentration is the mass amount of a dissolved substance in a certain volume of solution (for example: mg/l, g/m3).

Molar concentration

Molar concentration is the number of moles of a given substance dissolved in a certain volume of solution (mol/m3, mmol/l, µmol/ml).

Molal concentration

Molal concentration is the number of moles of a substance contained in 1000 g of solvent (mol/kg).

Normal solution

A solution is called normal if it contains one equivalent of a substance per unit volume, expressed in mass units: 1H = 1 mg eq/l = 1 mmol/l (indicating the equivalent of a specific substance).

Equivalent

Equivalent is equal to the ratio of the part of the mass of an element (substance) that adds or replaces one atomic mass of hydrogen or half in a chemical compound atomic mass oxygen, to 1/12 the mass of carbon 12. Thus, the equivalent of an acid is equal to its molecular weight, expressed in grams, divided by the basicity (the number of hydrogen ions); base equivalent - molecular weight divided by acidity (the number of hydrogen ions, and for inorganic bases - divided by the number of hydroxyl groups); salt equivalent - molecular weight divided by the sum of charges (valence of cations or anions); the equivalent of a compound participating in redox reactions is the quotient of the molecular weight of the compound divided by the number of electrons accepted (donated) by an atom of the reducing (oxidizing) element.

Relationships between units of measurement of the concentration of solutions
(Formula for transition from one expression of solution concentrations to another):

Accepted designations:

• ρ - solution density, g/cm 3 ;
• m is the molecular weight of the dissolved substance, g/mol;
• E is the equivalent mass of a solute, that is, the amount of substance in grams that interacts in a given reaction with one gram of hydrogen or corresponds to the transition of one electron.

According to GOST 8.417-2002 The unit of quantity of a substance is established: mole, multiples and submultiples ( kmol, mmol, µmol).

The SI unit of measurement for hardness is mmol/l; µmol/l.

In different countries, the abolished units for measuring water hardness often continue to be used:

• Russia and CIS countries - mEq/l, mcg-eq/l, g-eq/m 3 ;
• Germany, Austria, Denmark and some other countries of the Germanic group of languages ​​- 1 German degree - (Н° - Harte - hardness) ≡ 1 part CaO/100 thousand parts water ≡ 10 mg CaO/l ≡ 7.14 mg MgO/ l ≡ 17.9 mg CaCO 3 /l ≡ 28.9 mg Ca(HCO 3) 2 /l ≡ 15.1 mg MgCO 3 /l ≡ 0.357 mmol/l.
• 1 French degree ≡ 1 hour CaCO 3 /100 thousand parts water ≡ 10 mg CaCO 3 /l ≡ 5.2 mg CaO/l ≡ 0.2 mmol/l.
• 1 English degree ≡ 1 grain/1 gallon of water ≡ 1 part CaCO 3 /70 thousand parts water ≡ 0.0648 g CaCO 3 /4.546 l ≡ 100 mg CaCO3 /7 l ≡ 7.42 mg CaO/l ≡ 0.285 mmol /l. Sometimes the English degree of hardness is denoted Clark.
• 1 American degree ≡ 1 part CaCO 3 /1 million part water ≡ 1 mg CaCO 3 /l ≡ 0.52 mg CaO/l ≡ 0.02 mmol/l.

Here: part - part; the conversion of degrees into their corresponding amounts of CaO, MgO, CaCO 3, Ca(HCO 3) 2, MgCO 3 is shown as examples mainly for German degrees; Dimensions of degrees are tied to calcium-containing compounds, since calcium in the composition of hardness ions is usually 75-95%, in rare cases - 40-60%. Numbers are generally rounded to the second decimal place.

The relationship between units of water hardness:

1 mmol/l = 1 mg eq/l = 2.80°H (German degrees) = 5.00 French degrees = 3.51 English degrees = 50.04 American degrees.

A new unit of measurement of water hardness is the Russian degree of hardness - °Zh, defined as the concentration of an alkaline earth element (mainly Ca 2+ and Mg 2+), numerically equal to ½ its mole in mg/dm 3 (g/m 3).

Alkalinity units are mmol, µmol.

The SI unit of electrical conductivity is µS/cm.

The electrical conductivity of solutions and its inverse electrical resistance characterize the mineralization of solutions, but only the presence of ions. When measuring electrical conductivity, nonionic substances cannot be taken into account. organic matter, neutral suspended impurities, interference that distorts the results - gases, etc. It is impossible by calculation to accurately find the correspondence between the values ​​of specific electrical conductivity and the dry residue or even the sum of all separately determined substances of the solution, since in natural water different ions have different specific electrical conductivity, which simultaneously depends on the mineralization of the solution and its temperature. To establish such a dependence, it is necessary to experimentally establish the relationship between these quantities for each specific object several times a year.

• 1 µS/cm = 1 MΩ cm; 1 S/m = 1 Ohm m.

For pure solutions sodium chloride (NaCl) in distillate approximate ratio:

• 1 µS/cm ≈ 0.5 mg NaCl/l.

The same ratio (approximately), taking into account the above reservations, can be accepted for most natural waters with mineralization up to 500 mg/l (all salts are converted to NaCl).

When mineralization of natural water is 0.8-1.5 g/l, you can take:

• 1 µS/cm ≈ 0.65 mg salts/l,

and with mineralization - 3-5 g/l:

• 1 µS/cm ≈ 0.8 mg salts/l.

Content of suspended impurities in water, transparency and turbidity of water

Water turbidity is expressed in units:

• JTU (Jackson Turbidity Unit) - Jackson turbidity unit;
• FTU (Formasin Turbidity Unit, also designated EMF) - unit of turbidity for formazin;
• NTU (Nephelometric Turbidity Unit) - nephelometric turbidity unit.

It is impossible to give an exact ratio of turbidity units to suspended solids content. For each series of determinations, it is necessary to construct a calibration graph that allows you to determine the turbidity of the analyzed water in comparison with the control sample.

As a rough guide: 1 mg/l (suspended solids) ≡ 1-5 NTU units.

If the clouding mixture (diatomaceous earth) has a particle size of 325 mesh, then: 10 units. NTU ≡ 4 units JTU.

GOST 3351-74 and SanPiN 2.1.4.1074-01 equate to 1.5 units. NTU (or 1.5 mg/l for silica or kaolin) 2.6 units. FTU (EMF).

The relationship between font transparency and haze:

The relationship between transparency along the “cross” (in cm) and turbidity (in mg/l):

The SI unit of measurement is mg/l, g/m3, μg/l.

In the USA and some other countries, mineralization is expressed in relative units (sometimes in grains per gallon, gr/gal):

• ppm (parts per million) - part per million (1 · 10 -6) of a unit; sometimes ppm (parts per mille) also means a thousandth (1 · 10 -3) of a unit;
• ppb - (parts per billion) billionth (billionth) fraction (1 · 10 -9) of a unit;
• ppt - (parts per trillion) trillionth part (1 · 10 -12) of a unit;
• ‰ - ppm (also used in Russia) - thousandth (1 · 10 -3) of a unit.

The relationship between units of measurement of mineralization: 1 mg/l = 1ppm = 1 10 3 ppb = 1 10 6 ppt = 1 10 -3 ‰ = 1 10 -4%; 1 gr/gal = 17.1 ppm = 17.1 mg/l = 0.142 lb/1000 gal.

For measuring the salinity of salt waters, brines and salinity of condensates It is more correct to use units: mg/kg. In laboratories, water samples are measured by volume rather than by mass, so in most cases it is advisable to refer the amount of impurities to a liter. But for large or very small values ​​of mineralization the error will be sensitive.

According to SI, volume is measured in dm 3, but measurement is also allowed in liters, because 1 l = 1.000028 dm 3. Since 1964 1 l is equal to 1 dm 3 (exactly).

For salt waters and brines salinity units are sometimes used in degrees Baume(for mineralization >50 g/kg):

• 1°Be corresponds to a solution concentration equal to 1% in terms of NaCl.
• 1% NaCl = 10 g NaCl/kg.

Dry and calcined residue

Dry and calcined residues are measured in mg/l. The dry residue does not fully characterize the mineralization of the solution, since the conditions for its determination (boiling, drying the solid residue in an oven at a temperature of 102-110 ° C to constant weight) distort the result: in particular, part of the bicarbonates (conventionally accepted - half) decomposes and volatilizes in the form of CO 2.

Decimal multiples and submultiples of quantities

Decimal multiples and submultiple units of measurement of quantities, as well as their names and designations, should be formed using the factors and prefixes given in the table:

(based on materials from the site https://aqua-therm.ru/).

Physical size is a physical property of a material object, process, physical phenomenon, characterized quantitatively.

Physical quantity value expressed by one or more numbers characterizing this physical quantity, indicating the unit of measurement.

The size of a physical quantity are the values ​​of numbers appearing in the value of a physical quantity.

Units of measurement of physical quantities.

Unit of measurement of physical quantity is a quantity of fixed size that is assigned a numerical value equal to one. It is used for the quantitative expression of physical quantities homogeneous with it. A system of units of physical quantities is a set of basic and derived units based on a certain system of quantities.

Only a few systems of units have become widespread. In most cases, many countries use the metric system.

Basic units.

Measure a physical quantity - means to compare it with another similar physical quantity taken as a unit.

The length of an object is compared with a unit of length, the mass of a body with a unit of weight, etc. But if one researcher measures the length in fathoms and another in feet, it will be difficult for them to compare the two values. Therefore, all physical quantities throughout the world are usually measured in the same units. In 1963, the International System of Units SI (System international - SI) was adopted.

For each physical quantity in the system of units there must be a corresponding unit of measurement. Standard units is its physical implementation.

The length standard is meter- the distance between two strokes applied on a specially shaped rod made of an alloy of platinum and iridium.

Standard time serves as the duration of any regularly repeating process, for which the movement of the Earth around the Sun is chosen: the Earth makes one revolution per year. But the unit of time is taken not to be a year, but give me a sec.

For a unit speed take the speed of such uniform rectilinear motion at which the body moves 1 m in 1 s.

A separate unit of measurement is used for area, volume, length, etc. Each unit is determined when choosing a particular standard. But the system of units is much more convenient if only a few units are selected as the main ones, and the rest are determined through the main ones. For example, if the unit of length is a meter, then the unit of area will be a square meter, volume will be a cubic meter, speed will be a meter per second, etc.

Basic units The physical quantities in the International System of Units (SI) are: meter (m), kilogram (kg), second (s), ampere (A), kelvin (K), candela (cd) and mole (mol).

Basic SI units
Magnitude	Unit	Designation
	Name	Russian	international
Force electric current
Thermodynamic temperature
The power of light
Quantity of substance

There are also derived SI units that have their own names:

Derived SI units with their own names
	Unit		Derived unit expression
Magnitude	Name	Designation	Through other SI units	Through SI major and supplementary units
Pressure				m -1 ChkgChs -2
Energy, work, amount of heat				m 2 ChkgChs -2
Power, energy flow				m 2 ChkgChs -3
Amount of electricity, electric charge
Electrical voltage, electrical potential				m 2 ChkgChs -3 ChA -1
Electrical capacity				m -2 Chkg -1 Ch 4 Ch 2
Electrical resistance				m 2 ChkgChs -3 ChA -2
Electrical conductivity				m -2 Chkg -1 Ch 3 Ch 2
Magnetic induction flux				m 2 ChkgChs -2 ChA -1
Magnetic induction				kgHs -2 HA -1
Inductance				m 2 ChkgChs -2 ChA -2
Light flow
Illumination				m 2 ChkdChsr
Radioactive source activity	becquerel
Absorbed radiation dose

ANDmeasurements. To obtain an accurate, objective and easily reproducible description of a physical quantity, measurements are used. Without measurements, a physical quantity cannot be characterized quantitatively. Definitions such as “low” or “high” pressure, “low” or “high” temperature reflect only subjective opinions and do not contain comparisons with reference values. When measuring a physical quantity, a certain numerical value is assigned to it.

Measurements are carried out using measuring instruments. There are quite a large number of measuring instruments and devices, from the simplest to the most complex. For example, length is measured with a ruler or tape measure, temperature with a thermometer, width with calipers.

Measuring instruments are classified: by the method of presenting information (displaying or recording), by the method of measurement (direct action and comparison), by the form of presentation of readings (analog and digital), etc.

The following parameters are typical for measuring instruments:

Measuring range- the range of values ​​of the measured quantity for which the device is designed during its normal operation (with a given measurement accuracy).

Sensitivity threshold- the minimum (threshold) value of the measured value, distinguished by the device.

Sensitivity- connects the value of the measured parameter and the corresponding change in the instrument readings.

Accuracy- the ability of the device to indicate the true value of the measured indicator.

Stability- the ability of the device to maintain a given measurement accuracy for a certain time after calibration.

Since 1963, in the USSR (GOST 9867-61 “International System of Units”), in order to unify units of measurement in all fields of science and technology, the international (international) system of units (SI, SI) has been recommended for practical use - this is a system of units of measurement of physical quantities , adopted by the XI General Conference on Weights and Measures in 1960. It is based on 6 basic units (length, mass, time, electric current, thermodynamic temperature and luminous intensity), as well as 2 additional units ( flat angle, solid angle); all other units given in the table are their derivatives. The adoption of a unified international system of units for all countries is intended to eliminate the difficulties associated with the transfer of numerical values ​​of physical quantities, as well as various constants from any one currently operating system (GHS, MKGSS, ISS A, etc.) into another.

Name of quantity	Units; SI values	Designations
		Russian	international
I. Length, mass, volume, pressure, temperature
	Meter is a measure of length, numerically equal to the length of the international standard meter; 1 m=100 cm (1·10 2 cm)=1000 mm (1·10 3 mm)	m	m
	Centimeter = 0.01 m (1·10 -2 m) = 10 mm	cm	cm
	Millimeter = 0.001 m (1 10 -3 m) = 0.1 cm = 1000 μm (1 10 3 μm)	mm	mm
	Micron (micrometer) = 0.001 mm (1·10 -3 mm) = 0.0001 cm (1·10 -4 cm) = 10,000	mk	μ
	Angstrom = one ten-billionth of a meter (1·10 -10 m) or one hundred-millionth of a centimeter (1·10 -8 cm)	Å	Å
Weight	The kilogram is the basic unit of mass in the metric system of measures and the SI system, numerically equal to the mass of the international standard kilogram; 1 kg=1000 g	kg	kg
	Gram=0.001 kg (1·10 -3 kg)	G	g
	Ton= 1000 kg (1 10 3 kg)	T	t
	Centner = 100 kg (1 10 2 kg)	ts
	Carat - a non-systemic unit of mass, numerically equal to 0.2 g		ct
	Gamma = one millionth of a gram (1 10 -6 g)		γ
Volume	Liter = 1.000028 dm 3 = 1.000028 10 -3 m 3	l	l
Pressure	Physical, or normal, atmosphere - pressure balanced by a mercury column 760 mm high at a temperature of 0° = 1.033 atm = = 1.01 10 -5 n/m 2 = 1.01325 bar = 760 torr = 1.033 kgf/cm 2	atm	atm
	Technical atmosphere - pressure equal to 1 kgf/cmg = 9.81 10 4 n/m 2 = 0.980655 bar = 0.980655 10 6 dynes/cm 2 = 0.968 atm = 735 torr	at	at
	Millimeter of mercury = 133.32 n/m 2	mmHg Art.	mm Hg
	Tor is the name of a non-systemic unit of pressure measurement equal to 1 mm Hg. Art.; given in honor of the Italian scientist E. Torricelli	torus
	Bar - unit of atmospheric pressure = 1 10 5 n/m 2 = 1 10 6 dynes/cm 2	bar	bar
Pressure (sound)	Bar is a unit of sound pressure (in acoustics): bar - 1 dyne/cm2; Currently, a unit with a value of 1 n/m 2 = 10 dynes/cm 2 is recommended as a unit of sound pressure	bar	bar
	Decibel is a logarithmic unit of measurement of excess sound pressure level, equal to 1/10 of the unit of measurement of excess sound pressure - bela	dB	db
Temperature	Degree Celsius; temperature in °K (Kelvin scale), equal to temperature in °C (Celsius scale) + 273.15 °C	°C	°C
II. Force, power, energy, work, amount of heat, viscosity
Force	Dyna is a unit of force in the CGS system (cm-g-sec.), in which an acceleration of 1 cm/sec 2 is imparted to a body with a mass of 1 g; 1 din - 1·10 -5 n	ding	dyn
	Kilogram-force is a force that imparts an acceleration to a body with a mass of 1 kg equal to 9.81 m/sec 2 ; 1kg=9.81 n=9.81 10 5 din	kg, kgf
Power	Horsepower =735.5 W	l. With.	HP
Energy	Electron-volt is the energy that an electron acquires when moving in an electric field in a vacuum between points with a potential difference of 1 V; 1 eV = 1.6·10 -19 J. It is allowed to use multiple units: kiloelectron-volt (Kv) = 10 3 eV and megaelectron-volt (MeV) = 10 6 eV. In modern times, particle energy is measured in Bev - billions (billions) eV; 1 Bzv=10 9 eV	ev	eV
	Erg=1·10 -7 j; The erg is also used as a unit of work, numerically equal to the work done by a force of 1 dyne along a path of 1 cm	erg	erg
Job	Kilogram-force-meter (kilogrammometer) is a unit of work numerically equal to the work done by a constant force of 1 kg when moving the point of application of this force a distance of 1 m in its direction; 1 kGm = 9.81 J (at the same time kGm is a measure of energy)	kGm, kgf m	kGm
Quantity of heat	Calorie is an off-system unit of measurement of the amount of heat equal to the amount of heat required to heat 1 g of water from 19.5 ° C to 20.5 ° C. 1 cal = 4.187 J; common multiple unit kilocalorie (kcal, kcal), equal to 1000 cal	feces	cal
Viscosity (dynamic)	Poise is a unit of viscosity in the GHS system of units; viscosity at which in a layered flow with a velocity gradient equal to 1 sec -1 per 1 cm 2 of the layer surface, a viscous force of 1 dyne acts; 1 pz = 0.1 n sec/m 2	pz	P
Viscosity (kinematic)	Stokes is a unit of kinematic viscosity in the CGS system; equal to the viscosity of a liquid having a density of 1 g/cm 3 that resists a force of 1 dyne to the mutual movement of two layers of liquid with an area of ​​1 cm 2 located at a distance of 1 cm from each other and moving relative to each other at a speed of 1 cm per second	st	St
III. Magnetic flux, magnetic induction, magnetic field strength, inductance, electrical capacitance
Magnetic flux	Maxwell is a unit of measurement of magnetic flux in the CGS system; 1 μs is equal to the magnetic flux passing through an area of ​​1 cm 2 located perpendicular to the magnetic field induction lines, with an induction equal to 1 gf; 1 μs = 10 -8 wb (Weber) - units of magnetic current in the SI system	mks	Mx
Magnetic induction	Gauss is a unit of measurement in the GHS system; 1 gf is the induction of such a field in which a straight conductor 1 cm long, located perpendicular to the field vector, experiences a force of 1 dyne if a current of 3 10 10 CGS units flows through this conductor; 1 gs=1·10 -4 tl (tesla)	gs	Gs
Magnetic field strength	Oersted is a unit of magnetic field strength in the CGS system; one oersted (1 oe) is taken to be the intensity at a point in the field at which a force of 1 dyne (dyn) acts on 1 electromagnetic unit of the amount of magnetism; 1 e=1/4π 10 3 a/m	uh	Oe
Inductance	Centimeter is a unit of inductance in the CGS system; 1 cm = 1·10 -9 g (Henry)	cm	cm
Electrical capacity	Centimeter - unit of capacity in the CGS system = 1·10 -12 f (farads)	cm	cm
IV. Luminous intensity, luminous flux, brightness, illumination
The power of light	A candle is a unit of luminous intensity, the value of which is taken such that the brightness of the full emitter at the solidification temperature of platinum is equal to 60 sv per 1 cm2	St.	CD
Light flow	Lumen is a unit of luminous flux; 1 lumen (lm) is emitted within a solid angle of 1 ster from a point source of light having a luminous intensity of 1 light in all directions	lm	lm
	Lumen-second - corresponds to the light energy generated by a luminous flux of 1 lm emitted or perceived in 1 second	lm sec	lm·sec
	A lumen hour is equal to 3600 lumen seconds	lm h	lm h
Brightness	Stilb is a unit of brightness in the CGS system; corresponds to the brightness of a flat surface, 1 cm 2 of which gives in a direction perpendicular to this surface a luminous intensity equal to 1 ce; 1 sb=1·10 4 nits (nit) (SI unit of brightness)	Sat	sb
	Lambert is a non-systemic unit of brightness, derived from stilbe; 1 lambert = 1/π st = 3193 nt
	Apostilbe = 1/π s/m 2
Illumination	Phot - unit of illumination in the SGSL system (cm-g-sec-lm); 1 photo corresponds to the illumination of a surface of 1 cm2 with a uniformly distributed luminous flux of 1 lm; 1 f=1·10 4 lux (lux)	f	ph
V. Radiation intensity and dose
Intensity	Curie is the basic unit of measurement of the intensity of radioactive radiation, the curie corresponding to 3.7·10 10 decays per 1 second. any radioactive isotope	curie	C or Cu
	millicurie = 10 -3 curies, or 3.7 10 7 acts of radioactive decay in 1 second.	mcurie	mc or mCu
	microcurie= 10 -6 curie	mccurie	μC or μCu
Dose	X-ray - the number (dose) of X-rays or γ-rays, which in 0.001293 g of air (i.e. in 1 cm 3 of dry air at t° 0° and 760 mm Hg) causes the formation of ions carrying one electrostatic unit of quantity of electricity of each sign; 1 p causes the formation of 2.08 10 9 pairs of ions in 1 cm 3 of air	R	r
	milliroentgen = 10 -3 p	mr	mr
	microroentgen = 10 -6 p	microdistrict	μr
	Rad - the unit of absorbed dose of any ionizing radiation is equal to rad 100 erg per 1 g of irradiated medium; when air is ionized by X-rays or γ-rays, 1 r is equal to 0.88 rad, and when tissue is ionized, almost 1 r is equal to 1 rad	glad	rad
	Rem (biological equivalent of an x-ray) is the amount (dose) of any type of ionizing radiation that causes the same biological effect as 1 r (or 1 rad) of hard x-rays. Uneven biological effect with equal ionization different types radiation led to the need to introduce another concept: the relative biological effectiveness of radiation - RBE; the relationship between doses (D) and the dimensionless coefficient (RBE) is expressed as D rem = D rad RBE, where RBE = 1 for x-rays, γ-rays and β-rays and RBE = 10 for protons up to 10 MeV, fast neutrons and α - natural particles (according to the recommendation of the International Congress of Radiologists in Copenhagen, 1953)	reb, reb	rem

Note. Multiple and submultiple units of measurement, with the exception of units of time and angle, are formed by multiplying them by the appropriate power of 10, and their names are added to the names of the units of measurement. It is not allowed to use two prefixes to the name of the unit. For example, you cannot write millimicrowatt (mmkW) or micromicrofarad (mmf), but you must write nanowatt (nw) or picofarad (pf). Prefixes should not be applied to the names of such units that indicate a multiple or submultiple unit of measurement (for example, micron). To express the duration of processes and designate calendar dates of events, the use of multiple units of time is allowed.

The most important units of the International System of Units (SI)

Basic units
(length, mass, temperature, time, electric current, light intensity)

Name of quantity		Designations
		Russian	international
Length	Meter - length equal to 1650763.73 wavelengths of radiation in vacuum, corresponding to the transition between levels 2p 10 and 5d 5 of krypton 86 *	m	m
Weight	Kilogram - mass corresponding to the mass of the international standard kilogram	kg	kg
Time	Second - 1/31556925.9747 part of a tropical year (1900)**	sec	S, s
Electric current strength	Ampere is the strength of a constant current, which, passing through two parallel straight conductors of infinite length and negligible circular cross-section, located at a distance of 1 m from each other in a vacuum, would cause between these conductors a force equal to 2 10 -7 N per meter length	A	A
The power of light	A candle is a unit of luminous intensity, the value of which is taken such that the brightness of a complete (absolutely black) emitter at the solidification temperature of platinum is equal to 60 sec per 1 cm 2 ***	St.	CD
Temperature (thermodynamic)	Degree Kelvin (Kelvin scale) is a unit of measurement of temperature on the thermodynamic temperature scale, in which the temperature of the triple point of water**** is set to 273.16° K	°K	°K

* That is, the meter is equal to the indicated number of waves of radiation with a wavelength of 0.6057 microns, received from a special lamp and corresponding to the orange line of the spectrum of the neutral gas krypton. This definition of the unit of length makes it possible to reproduce the meter with the greatest accuracy, and most importantly, in any laboratory that has the appropriate equipment. In this case, there is no need to periodically check the standard meter with its international standard stored in Paris.
** That is, a second is equal to the specified part of the time interval between two successive passages of the Earth in orbit around the Sun of the point corresponding spring equinox. This gives greater accuracy in determining the second than defining it as a part of the day, since the length of the day varies.
*** That is, the luminous intensity of a certain reference source emitting light at the melting temperature of platinum is taken as a unit. The old international candle standard is 1.005 of the new candle standard. Thus, within the limits of normal practical accuracy, their values ​​can be considered identical.
**** Triple point - the temperature at which ice melts in the presence of saturated water vapor above it.

Additional and derived units

Name of quantity	Units; their definition	Designations
		Russian	international
I. Plane angle, solid angle, force, work, energy, amount of heat, power
Flat angle	Radian - the angle between two radii of a circle, cutting out an arc on the circle, the length of which is equal to the radius	glad	rad
Solid angle	Steradian is a solid angle whose vertex is located at the center of the sphere and which cuts out an area on the surface of the sphere equal to the area of ​​a square with a side equal to the radius of the sphere	erased	sr
Force	Newton is a force under the influence of which a body with a mass of 1 kg acquires an acceleration equal to 1 m/sec 2	n	N
Work, energy, amount of heat	Joule is the work done by a constant force of 1 N acting on a body along a path of 1 m traveled by the body in the direction of the force.	j	J
Power	Watt - power at which in 1 second. 1 J of work done	W	W
II. Amount of electricity, electrical voltage, electrical resistance, electrical capacitance
Amount of electricity, electric charge	Coulomb - the amount of electricity flowing through the cross-section of a conductor for 1 second. at a DC current of 1 A	To	C
Electrical voltage, electrical potential difference, electromotive force (EMF)	Volt is the voltage in a section of an electrical circuit through which 1 k of electricity passes through which 1 j of work is done.	V	V
Electrical resistance	Ohm - the resistance of a conductor through which, at a constant voltage at the ends of 1 V, a constant current of 1 A passes	ohm	Ω
Electrical capacity	Farad is the capacitance of a capacitor, the voltage between the plates of which changes by 1 V when charging it with an amount of electricity of 1 k.	f	F
III. Magnetic induction, magnetic flux, inductance, frequency
Magnetic induction	Tesla is the induction of a uniform magnetic field, which acts on a section of a straight conductor 1 m long, placed perpendicular to the direction of the field, with a force of 1 N when a direct current of 1 A passes through the conductor	tl	T
Magnetic induction flux	Weber - magnetic flux created by a uniform field with a magnetic induction of 1 T through an area of ​​1 m 2 perpendicular to the direction of the magnetic induction vector	wb	Wb
Inductance	Henry is the inductance of a conductor (coil) in which an emf of 1 V is induced when the current in it changes by 1 A in 1 second.	gn	H
Frequency	Hertz is the frequency of a periodic process in which in 1 sec. one oscillation occurs (cycle, period)	Hz	Hz
IV. Luminous flux, luminous energy, brightness, illumination
Light flow	Lumen is a luminous flux that gives within a solid angle of 1 ster a point source of light of 1 sv, emitting equally in all directions	lm	lm
Light energy	Lumen-second	lm sec	lm·s
Brightness	Nit is the brightness of a luminous plane, each square meter of which gives in the direction perpendicular to the plane, luminous intensity of 1 light	nt	nt
Illumination	Lux - illumination created by a luminous flux of 1 lm with its uniform distribution over an area of ​​1 m2	OK	lx
Lighting quantity	Lux second	lx sec	lx·s

In principle, one can imagine any large number of different systems of units, but only a few are widely used. All over the world, the metric system is used for scientific and technical measurements and in most countries in industry and everyday life.

Basic units.

In the system of units, for each measured physical quantity there must be a corresponding unit of measurement. Thus, a separate unit of measurement is needed for length, area, volume, speed, etc., and each such unit can be determined by choosing one or another standard. But the system of units turns out to be much more convenient if in it only a few units are selected as basic ones, and the rest are determined through the basic ones. So, if the unit of length is a meter, the standard of which is stored in the State Metrological Service, then the unit of area can be considered a square meter, the unit of volume is a cubic meter, the unit of speed is a meter per second, etc.

The convenience of such a system of units (especially for scientists and engineers, who deal with measurements much more often than other people) is that the mathematical relationships between the basic and derived units of the system turn out to be simpler. In this case, a unit of speed is a unit of distance (length) per unit of time, a unit of acceleration is a unit of change in speed per unit of time, a unit of force is a unit of acceleration per unit of mass, etc. In mathematical notation it looks like this: v = l/t, a = v/t, F = ma = ml/t 2. The presented formulas show the “dimension” of the quantities under consideration, establishing relationships between units. (Similar formulas allow you to determine units for quantities such as pressure or electric current.) Such relationships are of a general nature and are valid regardless of what units (meter, foot or arshin) the length is measured in and what units are chosen for other quantities.

In technology, the basic unit of measurement of mechanical quantities is usually taken not as a unit of mass, but as a unit of force. Thus, if in the system most commonly used in physical research, a metal cylinder is taken as a standard of mass, then in the technical system it is considered as a standard of force that balances the force of gravity acting on it. But since the force of gravity is not the same at different points on the Earth's surface, location specification is necessary to accurately implement the standard. Historically, the location was sea level at a latitude of 45°. Currently, such a standard is defined as the force necessary to give the specified cylinder a certain acceleration. True, in technology, measurements are usually not carried out with such high accuracy that it is necessary to take care of variations in gravity (if we are not talking about the calibration of measuring instruments).

There is a lot of confusion surrounding the concepts of mass, force and weight. The fact is that there are units of all these three quantities that have the same names. Mass is an inertial characteristic of a body, showing how difficult it is to remove it external force from a state of rest or uniform and linear motion. A unit of force is a force that, acting on a unit of mass, changes its speed by one unit of speed per unit of time.

All bodies attract each other. Thus, any body near the Earth is attracted to it. In other words, the Earth creates the force of gravity acting on the body. This force is called its weight. The force of weight, as stated above, is not the same at different points on the surface of the Earth and at different altitudes above sea level due to differences in gravitational attraction and in the manifestation of the Earth's rotation. However, the total mass of a given amount of substance is unchanged; it is the same both in interstellar space and at any point on Earth.

Precise experiments have shown that the force of gravity acting on different bodies (i.e. their weight) is proportional to their mass. Consequently, masses can be compared on scales, and masses that turn out to be the same in one place will be the same in any other place (if the comparison is carried out in a vacuum to exclude the influence of displaced air). If a certain body is weighed on a spring scale, balancing the force of gravity with the force of an extended spring, then the results of measuring the weight will depend on the place where the measurements are taken. Therefore, spring scales must be adjusted at each new location so that they correctly indicate the mass. The simplicity of the weighing procedure itself was the reason that the force of gravity acting on the standard mass was adopted as an independent unit of measurement in technology. HEAT.

Metric system of units.

The metric system is the general name for the international decimal system of units, the basic units of which are the meter and the kilogram. Although there are some differences in details, the elements of the system are the same throughout the world.

Story.

The metric system grew out of regulations adopted by the French National Assembly in 1791 and 1795 defining the meter as one ten-millionth of the portion of the earth's meridian from the North Pole to the equator.

By decree issued on July 4, 1837, the metric system was declared mandatory for use in all commercial transactions in France. It gradually replaced local and national systems in other European countries and was legally accepted as acceptable in the UK and USA. An agreement signed on May 20, 1875 by seventeen countries created international organization, designed to preserve and improve the metric system.

It is clear that by defining the meter as a ten-millionth part of a quarter of the earth's meridian, the creators of the metric system sought to achieve invariance and accurate reproducibility of the system. They took the gram as a unit of mass, defining it as the mass of one millionth of a cubic meter of water at its maximum density. Since it would not be very convenient to carry out geodetic measurements of a quarter of the earth's meridian with each sale of a meter of cloth or to balance a basket of potatoes at the market with the appropriate amount of water, metal standards were created that reproduced these ideal definitions with extreme accuracy.

It soon became clear that metal length standards could be compared with each other, introducing much less error than when comparing any such standard with a quarter of the earth's meridian. In addition, it became clear that the accuracy of comparing metal mass standards with each other is much higher than the accuracy of comparing any such standard with the mass of the corresponding volume of water.

In this regard, the International Commission on the Meter in 1872 decided to accept the “archival” meter stored in Paris “as it is” as the standard of length. Similarly, the members of the Commission accepted the archival platinum-iridium kilogram as the standard of mass, “considering that the simple relationship established by the creators of the metric system between the unit of weight and the unit of volume is represented by the existing kilogram with an accuracy sufficient for ordinary applications in industry and commerce, and the exact Sciences do not need a simple numerical relationship of this kind, but an extremely perfect definition of this relationship.” In 1875, many countries around the world signed a meter agreement, and this agreement established a procedure for coordinating metrological standards for the world scientific community through the International Bureau of Weights and Measures and the General Conference on Weights and Measures.

The new international organization immediately began developing international standards for length and mass and transmitting copies of them to all participating countries.

Standards of length and mass, international prototypes.

The international prototypes of the standards of length and mass - the meter and the kilogram - were deposited with the International Bureau of Weights and Measures, located in Sèvres, a suburb of Paris. The meter standard was a ruler made of a platinum alloy with 10% iridium, the cross-section of which was given a special X-shape to increase bending rigidity with a minimum volume of metal. In the groove of such a ruler there was a longitudinal flat surface, and the meter was defined as the distance between the centers of two strokes applied across the ruler at its ends, at a standard temperature of 0 ° C. The mass of a cylinder made of the same platinum was taken as the international prototype of the kilogram. iridium alloy, the same as the standard meter, with a height and diameter of about 3.9 cm. The weight of this standard mass, equal to 1 kg at sea level at latitude 45°, is sometimes called kilogram-force. Thus, it can be used either as a standard of mass for an absolute system of units, or as a standard of force for a technical system of units in which one of the basic units is the unit of force.

The international prototypes were selected from a large batch of identical standards produced simultaneously. Other standards of this batch were transferred to all participating countries as national prototypes (state primary standards), which are periodically returned to the International Bureau for comparison with international standards. Comparisons made at various times since then show that they do not show deviations (from international standards) beyond the limits of measurement accuracy.

International SI system.

The metric system was very favorably received by scientists of the 19th century. partly because it was proposed as an international system of units, partly because its units were theoretically assumed to be independently reproducible, and also because of its simplicity. Scientists began to develop new units for the various physical quantities they dealt with, based on the elementary laws of physics and linking these units to the metric units of length and mass. The latter increasingly conquered various European countries, in which previously many unrelated units for different quantities were in use.

Although all countries that adopted the metric system of units had nearly identical standards for metric units, various discrepancies in derived units arose between different countries and different disciplines. In the field of electricity and magnetism, two separate systems of derived units emerged: electrostatic, based on the force with which two electric charges act on each other, and electromagnetic, based on the force of interaction between two hypothetical magnetic poles.

The situation became even more complicated with the advent of the so-called system. practical electrical units introduced in the mid-19th century. by the British Association for the Advancement of Science to meet the demands of rapidly developing wire telegraph technology. Such practical units do not coincide with the units of both systems mentioned above, but differ from the units of the electromagnetic system only by factors equal to whole powers of ten.

Thus, for such common electrical quantities as voltage, current and resistance, there were several options for accepted units of measurement, and each scientist, engineer, and teacher had to decide for himself which of these options was best for him to use. In connection with the development of electrical engineering in the second half of the 19th and first half of the 20th centuries. Practical units were increasingly used and eventually came to dominate the field.

To eliminate such confusion at the beginning of the 20th century. a proposal was put forward to combine practical electrical units with corresponding mechanical ones based on metric units of length and mass, and build some kind of coherent system. In 1960, the XI General Conference on Weights and Measures adopted a single International system units (SI), defined the basic units of this system and prescribed the use of certain derived units, “without prejudice to others that may be added in the future.” Thus, for the first time in history international agreement The International Coherent System of Units was adopted. It is now accepted as a legal system of units of measurement by most countries in the world.

The International System of Units (SI) is a harmonized system that provides one and only one unit of measurement for any physical quantity, such as length, time, or force. Some of the units are given special names, an example is the unit of pressure pascal, while the names of others are derived from the names of the units from which they are derived, for example the unit of speed - meter per second. The basic units, together with two additional geometric ones, are presented in Table. 1. Derived units for which special names are adopted are given in table. 2. Of all the derived mechanical units, the most important are the unit of force newton, the unit of energy the joule and the unit of power the watt. Newton is defined as the force that imparts an acceleration of one meter per second squared to a mass of one kilogram. A joule is equal to the work done when the point of application of a force equal to one Newton moves a distance of one meter in the direction of the force. A watt is the power at which one joule of work is done in one second. Electrical and other derived units will be discussed below. The official definitions of major and minor units are as follows.

A meter is the length of the path traveled by light in a vacuum in 1/299,792,458 of a second. This definition was adopted in October 1983.

A kilogram is equal to the mass of the international prototype of the kilogram.

A second is the duration of 9,192,631,770 periods of radiation oscillations corresponding to transitions between two levels of the hyperfine structure of the ground state of the cesium-133 atom.

Kelvin is equal to 1/273.16 of the thermodynamic temperature of the triple point of water.

A mole is equal to the amount of a substance that contains the same number of structural elements as atoms in the carbon-12 isotope weighing 0.012 kg.

A radian is a plane angle between two radii of a circle, the length of the arc between which is equal to the radius.

The steradian is equal to the solid angle with its vertex at the center of the sphere, cutting out on its surface an area equal to the area of ​​a square with a side equal to the radius of the sphere.

To form decimal multiples and submultiples, a number of prefixes and factors are prescribed, indicated in the table. 3.

Table 3. Prefixes and multipliers of the international system of units
exa			deci
peta			centi
tera			Milli
giga			micro	mk
mega			nano
kilo			pico
hecto			femto
soundboard	Yes		atto

Thus, a kilometer (km) is 1000 m, and a millimeter is 0.001 m. (These prefixes apply to all units, such as kilowatts, milliamps, etc.)

It was originally intended that one of the base units should be the gram, and this was reflected in the names of the units of mass, but nowadays the base unit is the kilogram. Instead of the name megagram, the word “ton” is used. In physics disciplines, such as measuring the wavelength of visible or infrared light, a millionth of a meter (micrometer) is often used. In spectroscopy, wavelengths are often expressed in angstroms (Å); An angstrom is equal to one tenth of a nanometer, i.e. 10 - 10 m. For radiation with a shorter wavelength, such as X-rays, in scientific publications it is allowed to use a picometer and an x-unit (1 x-unit = 10 –13 m). A volume equal to 1000 cubic centimeters (one cubic decimeter) is called a liter (L).

Mass, length and time.

All basic SI units, except the kilogram, are currently defined in terms of physical constants or phenomena that are considered immutable and reproducible with high accuracy. As for the kilogram, a way to implement it with the degree of reproducibility that is achieved in procedures for comparing various mass standards with the international prototype of the kilogram has not yet been found. Such a comparison can be carried out by weighing on a spring balance, the error of which does not exceed 1H 10 –8. Standards of multiple and submultiple units for a kilogram are established by combined weighing on scales.

Since the meter is defined in terms of the speed of light, it can be reproduced independently in any well-equipped laboratory. Thus, using the interference method, line and end length measures, which are used in workshops and laboratories, can be checked by comparing directly with the wavelength of light. The error with such methods under optimal conditions does not exceed one billionth (1H 10 –9). With the development of laser technology, such measurements have become very simplified, and their range has expanded significantly.

Likewise, the second, according to its modern definition, can be independently realized in a competent laboratory in an atomic beam facility. The beam's atoms are excited by a high-frequency oscillator tuned to the atomic frequency, and an electronic circuit measures time by counting the periods of oscillation in the oscillator circuit. Such measurements can be carried out with an accuracy of the order of 1H 10 -12 - much higher than was possible with previous definitions of the second, based on the rotation of the Earth and its revolution around the Sun. Time and it reciprocal– frequency – are unique in that their standards can be transmitted by radio. Thanks to this, anyone who has the appropriate radio receiving equipment can receive signals of exact time and reference frequency, almost no different in accuracy from those transmitted over the air.

Mechanics.

Temperature and warmth.

Mechanical units do not allow solving all scientific and technical problems without involving any other relationships. Although the work done when moving a mass against the action of a force, and the kinetic energy of a certain mass are equivalent in nature to the thermal energy of a substance, it is more convenient to consider temperature and heat as separate quantities that do not depend on mechanical ones.

Thermodynamic temperature scale.

The unit of thermodynamic temperature Kelvin (K), called kelvin, is determined by the triple point of water, i.e. the temperature at which water is in equilibrium with ice and steam. This temperature is taken to be 273.16 K, which determines the thermodynamic temperature scale. This scale, proposed by Kelvin, is based on the second law of thermodynamics. If there are two thermal reservoirs with a constant temperature and a reversible heat engine transferring heat from one of them to the other in accordance with the Carnot cycle, then the ratio of the thermodynamic temperatures of the two reservoirs is given by T 2 /T 1 = –Q 2 Q 1 where Q 2 and Q 1 – the amount of heat transferred to each of the reservoirs (the minus sign indicates that heat is taken from one of the reservoirs). Thus, if the temperature of the warmer reservoir is 273.16 K, and the heat taken from it is twice as much as the heat transferred to the other reservoir, then the temperature of the second reservoir is 136.58 K. If the temperature of the second reservoir is 0 K, then it no heat will be transferred at all, since all the gas energy has been converted into mechanical energy in the adiabatic expansion section of the cycle. This temperature is called absolute zero. Thermodynamic temperature commonly used in scientific research, coincides with the temperature included in the equation of state of an ideal gas PV = RT, Where P- pressure, V– volume and R– gas constant. The equation shows that for an ideal gas, the product of volume and pressure is proportional to temperature. This law is not exactly satisfied for any of the real gases. But if corrections are made for virial forces, then the expansion of gases allows us to reproduce the thermodynamic temperature scale.

International temperature scale.

In accordance with the definition outlined above, temperature can be measured with very high accuracy (up to approximately 0.003 K near the triple point) by gas thermometry. A platinum resistance thermometer and a gas reservoir are placed in a thermally insulated chamber. When the chamber is heated, the electrical resistance of the thermometer increases and the gas pressure in the reservoir increases (in accordance with the equation of state), and when cooled, the opposite picture is observed. By measuring resistance and pressure simultaneously, you can calibrate the thermometer by gas pressure, which is proportional to temperature. The thermometer is then placed in a thermostat in which the liquid water can be kept in equilibrium with its solid and vapor phases. By measuring its electrical resistance at this temperature, a thermodynamic scale is obtained, since the temperature of the triple point is assigned a value equal to 273.16 K.

There are two international temperature scales - Kelvin (K) and Celsius (C). Temperature on the Celsius scale is obtained from temperature on the Kelvin scale by subtracting 273.15 K from the latter.

Accurate temperature measurements using gas thermometry require a lot of labor and time. Therefore, the International Practical Temperature Scale (IPTS) was introduced in 1968. Using this scale, thermometers different types can be calibrated in the laboratory. This scale was established using a platinum resistance thermometer, a thermocouple and a radiation pyrometer, used in the temperature intervals between certain pairs of constant reference points (temperature benchmarks). The MPTS was supposed to correspond to the thermodynamic scale with the greatest possible accuracy, but, as it turned out later, its deviations were very significant.

Fahrenheit temperature scale.

The Fahrenheit temperature scale, which is widely used in combination with the British technical system units, as well as in non-scientific measurements in many countries, are usually determined by two constant reference points - the melting temperature of ice (32° F) and the boiling point of water (212° F) at normal (atmospheric) pressure. Therefore, to get the Celsius temperature from the Fahrenheit temperature, you need to subtract 32 from the latter and multiply the result by 5/9.

Units of heat.

Since heat is a form of energy, it can be measured in joules, and this metric unit has been adopted by international agreement. But since the amount of heat was once determined by the change in temperature of a certain amount of water, a unit called a calorie became widespread and is equal to the amount of heat required to increase the temperature of one gram of water by 1 ° C. Due to the fact that the heat capacity of water depends on temperature , I had to clarify the calorie value. At least two appeared different calories– “thermochemical” (4.1840 J) and “steam” (4.1868 J). The “calorie” used in dietetics is actually a kilocalorie (1000 calories). The calorie is not an SI unit and has fallen into disuse in most fields of science and technology.

Electricity and magnetism.

All commonly accepted electrical and magnetic units of measurement are based on the metric system. In accordance with modern definitions of electrical and magnetic units, they are all derived units, derived by certain physical formulas from the metric units of length, mass and time. Since most electrical and magnetic quantities are not so easy to measure using the standards mentioned, it was found that it is more convenient to establish, through appropriate experiments, derivative standards for some of the indicated quantities, and to measure others using such standards.

SI units.

Below is a list of SI electrical and magnetic units.

The ampere, a unit of electric current, is one of the six SI base units. Ampere is the strength of a constant current, which, when passing through two parallel straight conductors of infinite length with a negligibly small circular cross-sectional area, located in a vacuum at a distance of 1 m from each other, would cause on each section of the conductor 1 m long an interaction force equal to 2H 10 - 7 N.

Volt, a unit of potential difference and electromotive force. Volt is the electrical voltage in a section of an electrical circuit with a direct current of 1 A with a power consumption of 1 W.

Coulomb, a unit of quantity of electricity (electric charge). Coulomb is the amount of electricity passing through the cross-section of a conductor at a constant current of 1 A in 1 s.

Farad, a unit of electrical capacitance. Farad is the capacitance of a capacitor on the plates of which, when charged at 1 C, an electric voltage of 1 V appears.

Henry, unit of inductance. Henry is equal to the inductance of the circuit in which a self-inductive emf of 1 V occurs when the current in this circuit changes uniformly by 1 A in 1 s.

Weber unit of magnetic flux. Weber is a magnetic flux, when it decreases to zero, an electric charge equal to 1 C flows in the circuit connected to it, which has a resistance of 1 Ohm.

Tesla, a unit of magnetic induction. Tesla is the magnetic induction of a uniform magnetic field, in which the magnetic flux through a flat area of ​​1 m2, perpendicular to the induction lines, is equal to 1 Wb.

Practical standards.

Light and illumination.

Luminous intensity and illuminance units cannot be determined based on mechanical units alone. We can express the energy flux in a light wave in W/m2, and the intensity of the light wave in V/m, as in the case of radio waves. But the perception of illumination is a psychophysical phenomenon in which not only the intensity of the light source is significant, but also the sensitivity of the human eye to the spectral distribution of this intensity.

By international agreement, the unit of luminous intensity is the candela (previously called a candle), equal to the luminous intensity in a given direction of a source emitting monochromatic radiation of frequency 540H 10 12 Hz ( l= 555 nm), energetic force the light radiation of which in this direction is 1/683 W/sr. This roughly corresponds to the luminous intensity of a spermaceti candle, which once served as a standard.

If the luminous intensity of the source is one candela in all directions, then the total luminous flux is 4 p lumens. Thus, if this source is located at the center of a sphere with a radius of 1 m, then the illumination of the inner surface of the sphere is equal to one lumen per square meter, i.e. one suite.

X-ray and gamma radiation, radioactivity.

X-ray (R) is an obsolete unit of exposure dose of x-ray, gamma and photon radiation, equal to the amount of radiation that, taking into account secondary electron radiation, forms ions in 0.001 293 g of air that carry a charge equal to one unit of the CGS charge of each sign. The SI unit of absorbed radiation dose is the gray, equal to 1 J/kg. The standard for absorbed radiation dose is a setup with ionization chambers that measure the ionization produced by radiation.

Contents:

Electric current is characterized by quantities such as current, voltage and resistance that are interconnected. Before considering the question of how voltage is measured, it is necessary to find out exactly what this quantity is and what its role is in the formation of current.

How does tension work?

The general concept of electric current is the directed movement of charged particles. These particles are electrons, the movement of which occurs under the influence of an electric field. The more charges need to be moved, the more work is done by the field. This work is affected not only by current, but also by voltage.

The physical meaning of this value is that the work done by the current in any section of the circuit is correlated with the amount of charge that passes through this section. In the process of this work, a positive charge moves from a point where there is a small potential to a point with a high potential. Thus, voltage is defined as electromotive force, and work itself is energy.

The work done by an electric current is measured in joules (J), and the amount of electric charge is a coulomb (C). As a result, the voltage is a ratio of 1 J/C. The resulting unit of voltage is called a volt.

To clearly explain the physical meaning of stress, you need to refer to the example of a hose filled with water. In this case, the volume of water will play the role of current strength, and its pressure will be equivalent to voltage. When water moves without a tip, it is free and in large quantities moves along the hose, creating low pressure. If you press the end of the hose with your finger, the volume will decrease while the water pressure increases. The jet itself will travel a much greater distance.

The same thing happens in electricity. The strength of the current is determined by the number or volume of electrons moving through the conductor. The voltage value is essentially the force with which those electrons are pushed through. It follows that, given the same voltage, a conductor that conducts a larger amount of current must also have a larger diameter.

Voltage unit

The voltage can be constant or variable, depending on the current. This value can be designated as the letter B (Russian designation) or V, corresponding to the international designation. To indicate alternating voltage, the “~” symbol is used, which is placed in front of the letter. For constant voltage there is a “-” sign, but in practice it is almost never used.

When considering the question of how voltage is measured, it should be remembered that there are not only volts for this. Larger quantities are measured in kilovolts (kV) and megavolts (mV), which means 1 thousand and 1 million volts, respectively.

How to measure voltage and current