Emerson Exchange 365

First, do you really need to calibrate (perform sensor trim)? Have the transmitters drifted? If the transmitters are new from the factory you don’t really need to calibrate (trim) them because they are already calibrated in the factory using precision equipment. If you calibrate in the field, you might inadvertently make it worse. Especially if you can’t get the right equipment. The reason I ask is because sometimes I come across projects where they calibrate pressure and temperature transmitters (but not level, flow, and the others) as a routine procedure even though not required. But sure, in case the transmitters have been in operation for a couple of years then calibration may be required.

Anyway, back to your question, if you apply 0 psig (i.e. sensor open to atmosphere) then the transmitter display and digital reading should be about 14.7 psia (you have to check the atmospheric pressure at site since it depends on altitude and weather etc.) and you should get 14.7/1000*16+4=4.24 mA. When you apply 1000-14.7=985.3 psig you should read 1000 psia on the display and get 20 mA.

See the calibration trim tutorial found here:
www.eddl.org/.../Calibration.aspx

In reply to Jonas Berge:

I agree with Jonas, there is no portable equipment on the market that can calibrate a pressure transmitter better than the equipment at the factory so unless there are indications that a calibration needs be performed, it is best to leave it alone. Especially a zero trim as it is virtually impossible to do that in the field.
The procedure to check the calibration would be to first call your local airport and get the barometric pressure, yes, it will be a little different as your latititude and elevation is different but the error would be minute compared to the pressure range you are calibrating. I would then open the transmitter to atmosphere and compare the digitial value, the PV, to the value you got from the airport. If the difference between the PV and the airport value is outside your calibration tolerance, I would go to Maintenance, Calibration, and select Reset to Factory Calibration. This will set the transmitters calibration back to what it was when it left the factory, basically undoing any calibration the last person might have done and maybe done wrong. Compare the PV with the airport reading again. If it is still outside your calibration tolerance, with he transmitter open to atmosphere, I would do an upper sensor trim and when asked to input the applied pressure, enter the airport barametric pressure. Again their might be a slight barametric pressure error from the airport to your location but it is minute compared to your pressure range.
Saying that, if you have to, it looks like Fluke makes an absolute pressure module in the range you are looking for in the 750 series. Those should work for you.