D6F-series MEMS Flaw Sensor User’s Manual (A286)
20
Volumetric flow rate and Mass flow rate
The volumetric flow rate is the volume of gas flowing per unit time. It is proportional to the
temperature, which is inversely proportional to the pressure. It is described as m
3
/s, m
3
/min, L/s, or
L/min in case of SI unit. The volume of gas is influenced by the pressure and the temperature, so
then the condition of the pressure and the temperature should be considered in case of the
volumetric flow rate.
On the other hand, the mass flow rate is the mass of gas flowing per unit time. It does not depend
on the temperature and the pressure. It is described as kg/s, kg/min in case of SI unit. OMRON’s
MEMS flow sensor will output an equivalent value with the mass flow rate.
Normal Volumetric Flow Rate and Standard Volumetric Flow Rate
To define this mass flow rate, it is common to express as the volumetric flow rate at the conditions
which defines the pressure and temperature. The condition of the pressure and temperature are
1atm (101.3kPa) and 0 degree C. Under this condition, the volumetric flow rate value is expressed
as NLM (Normal Liters per Minute) or SLM (Standard Liters per Minute). Each company has each
condition of this pressure and temperature and there is no rule in particular. Please be sure to
check the standard condition of the product before use.
