For transmitters, why is the calibration range always mentioned in mm of WC? How is the calibration range selected? I have a DPT with differential pressure range 0 to 0.1 kg/cm2. What shall be its calibration range?

 

The range can be in any pressure unit. Your calibration range is whatever you want to measure.

Roy

 

About Water Column:
When I started my career (25 yrs ago) in instrumentation water filled U-tubes, easily determined in mm or inches, was still commonly used for calibration of dp-transmitters. You can read more on this link:
http://www.flowcontrolnetwork.com/issuearticle.asp?ArticleID=262
"it was convenient to express the calibration as the height of water in the U-tube."

About calibration:
I would calibrate (compare to reference meter) at 0% and 100%, and at least one additional point, on mid scale maybe 60% to verify linearity.

/Ulf