Hi,
I've bought a VOCs gas sensor from IDT (SGAS707), with the purpose of measuring the concentration of some volatile gases in air. In the datasheet of the sensor there are some examples of typical responses of some gases (R x Concentration, once the sensor works with resistance). The concentration is in ppm. Do you know what units are typically used in these sensors? For example, mg of gas/ m3 of air or V/V?
The ppm (parts-per-million) is a relative / dimensionless value, e.g., mole fraction (mkmol /mol), mass fraction (mg / kg) or volume fraction (cm3 / m3) used in chemistry, biology, and toxicology. Sometimes people consider that 1 ppm = 1 mg / L. This may be true for aqueous solutions, since the density of water is ~1 kg / L, but this is wrong for gases, since their density varies from 1.2 g/L (air) to 0.7 g / L (methane). Be careful!
I guess it is parts-per-million, so relative concentration in terms of number of molecules
1 ppm = 1 cm3 vapour of the volatile compound at the ambient temperature and pressure/ 1 m3 air (same T,P). All definitions (V/V, P/P, n/n) produce the same concentration value.
The unit ppm (parts per milion) is often used for gas concentration. For the details of a convertation of ppm into other units, see e.g., https://www.lenntech.com/calculators/ppm/converter-parts-per-million.htm.
The ppm (parts-per-million) is a relative / dimensionless value, e.g., mole fraction (mkmol /mol), mass fraction (mg / kg) or volume fraction (cm3 / m3) used in chemistry, biology, and toxicology. Sometimes people consider that 1 ppm = 1 mg / L. This may be true for aqueous solutions, since the density of water is ~1 kg / L, but this is wrong for gases, since their density varies from 1.2 g/L (air) to 0.7 g / L (methane). Be careful!
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