It's possible to make a valid verification check of a Michell Easidew dew-point transmitter in the field. The simplest way to verify the performance of the sensor by using gas with a certified H2O content.
Cylinders of gas (N2 is fine) with certified H2O content are available from most specialty gas producers but it is crucial to buy a cylinder with a certificate and stated uncertainty, as without a known reference the results of your test will be invalid.
Ensure that you specify an H2O content which is as close to your typical measurement point as possible. Ideally it should be slightly wetter than the typical measurement to reduce test time and gas consumption.
You will also need the following items:
The test procedure is as follows:
|Dew-Point Temperature °Cdp||Minimum Stabilisation Time|
Note: to limit the effects of temperature on the adsorption/desorption rates of moisture in the regulator and tubing, time this test to begin at the time of day when the temperature is as stable as possible. Ideally conduct the test in a temperature stable environment.
The alternatives to the above are:
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