Automatic compensation of flowmeter errors due to variations in the expansion coefficient of the measured medium

Conclusions

• 1) The gas and vapor measurement error due to variations of factor ε can attain large proportions (±5% or more) and, therefore, even for constant parameters of the measured gas or vapor it may become necessary to compensate automatically this error.

• 2) When variations of ε are accounted for automatically it is advisable to design the constricting device on the basis of the value of ε_d which corresponds to the maximum pressure drop.

• 3) The flowmeter error due to variations of ε can be compensated electrically or pneumatically, by means of a functional transducer or by changing the cam profile. In the latter case it is necessary to have several standard sizes of cams in order to cover the entire ε variations range.

• 4) The compensation of the ε error in flowmeters with a variable pressure drop can, in many cases, extend their application range.