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In science and engineering, the parts-per notation is a set of pseudo-units to describe small values of miscellaneous dimensionless quantities, e.g. mole fraction or mass fraction. Since these fractions are quantity-per-quantity measures, they are pure numbers with no associated units of measurement. Commonly used are parts-per-million ( ppm ...
Wind speed conversion factors. Meteorological data includes wind speeds which may be expressed as statute miles per hour, knots, or meters per second. Here are the conversion factors for those various expressions of wind speed: 1 m/s = 2.237 statute mile/h = 1.944 knots. 1 knot = 1.151 statute mile/h = 0.514 m/s.
Correcting concentrations for altitude. Air pollutant concentrations expressed as mass per unit volume of atmospheric air (e.g., mg/m 3, μg/m 3, etc.) at sea level will decrease with increasing altitude. The concentration decrease is directly proportional to the pressure decrease with increasing altitude.
Grain per gallon. The grain per gallon ( gpg) is a unit of water hardness defined as 1 grain (64.8 milligrams) of calcium carbonate dissolved in 1 US gallon of water (3.785412 L ). It translates into 1 part in about 58,000 parts of water or 17.1 parts per million (ppm). Also called Clark degree (in terms of an imperial gallon ).
where TDS is expressed in mg/L and EC is the electrical conductivity in microsiemens per centimeter at 25 °C. The conversion factor k e varies between 0.55 and 0.8. [5] Some TDS meters use an electrical conductivity measurement to the ppm using the above formula. Regarding units, 1 ppm indicates 1 mg of dissolved solids per 1000 g of water. [6]
Standard cubic centimeters per minute ( SCCM) is a unit used to quantify the flow rate of a fluid. 1 SCCM is identical to 1 cm³ STP /min. Another expression of it would be Nml/min. These standard conditions vary according to different regulatory bodies.
It is also possible to use other units. For example, in the 1930s Widmark measured alcohol and blood by mass, and thus reported his concentrations in units of g/kg or mg/g, weight alcohol per weight blood. 1 mL of blood has a mass of approximately 1.055 grams, thus a mass-volume BAC of 1 g/L corresponds to a mass-mass BAC of 0.948 mg/g.
Carbonate hardness, is a measure of the water hardness caused by the presence of carbonate ( CO2−. 3) and bicarbonate ( HCO−. 3) anions. Carbonate hardness is usually expressed either in degrees KH ( °dKH) (from the German "Karbonathärte" ), or in parts per million calcium carbonate ( ppm CaCO. 3 or grams CaCO.