Agilent Flowmeter ADM2000
6
Operating Instructions
Important
When compared with readings from the ADM2000, measure-
ments taken with bubble-type flowmeters may show a differ-
ence. This is not a problem with your new ADM2000.
As a consequence of the ideal gas law, measurements made
with both soap bubble meters and the ADM2000 are tempera-
ture sensitive. However, bubble-type flowmeters add water
vapor to the gas being measured which introduces error into
the flow rate measurement.
Even when accurately calibrated, soap bubble meters typically
read slightly higher than the ADM2000. The higher readings
arise from relatively high concentrations of water vapor
present in the soap bubble apparatus. At room temperature,
water vapor can raise readings by nearly 4%. This unfortunate
property is amplified by the effect of temperature. As the mea-
sured gas or the flowmeter itself is warmed, the amount of
water vapor increases, and the readings can be much higher
than the true flow rate. Figure 1 shows the effect of water
vapor on volumetric flow measurements. Since the ADM2000
is bubble-free, this error is not introduced into the flow rate
measurement.
