Thoughts on the difference between the calibration and re-ranging of a pressure transmitter. Take a rosemount 3051 smart transmitter recently calibrated to measure flow 0-100m3/hr with sq/rt being applied at the trip amp.
Now, a few weeks later, the trip amp is removed from the loop, the range is changed to 0-200m3/hr and sq/rt is applied in the transmitter head.
The question is: should the transmitter now have a function test conducted on it such as having its calibration checked?
The present day spec for drift-over-time is so good that I probably wouldn't bother checking. I'd assume the performance is more than adequate after the range change. But it's your call.
Someone has already re-ranged the transmitter from 0-100m3/hr to 0-200m3/hr, so you don't call re-ranging 'calibration' (a lot of people do).
The two calibration adjustments that can be made to most smart transmitters are
- sensor trim
- current output trim
where calibration means
- compare the transmitter's pressure readings to a pressure reference standard to see if adjustment needs to be done or
- compare the current output values to a reference standard and adjust if need be."
Making the cal check requires a calibration reference sources and some means of implementing an adjustment, like a handheld communicator or pushbuttons and display, depending on the model or a reference grade current source and current calibrator.