Volumetric Vs. Mass Flow Measurements; Bubble Flowmeters - Restek ProFLOW 6000 User Manual

11.0 Volumetric vs. mass flow measurements

The Restek ProFLOW 6000 is a volumetric flow measurement device. Volumetric flow is the measure-
ment of the volume of gas through a conveyance per quantity of time. Standard units of measure for
this parameter are given in mL/min. The advantage of measuring volumetric flow is its independence to
the composition of the flow gas. It is not necessary to correct the flow values based on the gas composi-
tion, as is required for mass flow devices.
Mass flow measures the weight of the gas flowing through the instrument per quantity of time. Mass
flow units of measure are commonly g/sec.
12.0 Bubble flowmeter measurements
If you employ bubble flowmeters in your laboratory, you may find that they give slightly different flow
rate values than the Restek ProFLOW 6000. This error is due to technology limitations inherent in
the bubble flowmeter device, error from variances in air humidity within the bubble chamber, and its
direct contribution to the measured flow rate. In the event a bubble flowmeter is used to measure flow
gas where the gas is at elevated temperatures, the error due to humidity contributions can be extreme.
For the most accurate measurement of laboratory gas flow rates, we recommend using the Restek
ProFLOW 6000 over bubble flowmeters.
www.restek.com
- 15 -