One of the easiest ways to reduce errors during flow measurements is to lower the connecting volume between the calibrator and the device under test. Mesa Laboratories piston provers were designed to minimize connecting volume effects, but reducing the connecting volume proportionately reduces measurement errors.
If lowering the connecting volume is not possible, adding a backpressure regulator may also lower effects from large connecting volumes. Flow measurements can also be corrected for connecting volume using pressure, volume and measured flow rates (see equation below).
Fcor = flow corrected for connecting volume
F = measured flow
P2= gas pressure at end of gas flow measurement interval
Pa = standardizing or ambient gas pressure
P1 = gas pressure at beginning of flow measurement interval
Vconn = estimated minimum connecting volume
For a more detailed application note regarding errors and connecting volumes, take a look at Mesa Lab’s “What You Should Know about Connecting Volume” document.