How To Calibrate a P/I Transmitter in a Classified Location

How To Calibrate a P/I Transmitter in a Classified Location- With a built-in hand pump, precision measurement of both pressure and current, the Fluke 718Ex Pressure Calibrator is a complete, self-contained tool for  the calibration of P/I transmitters. To calibrate a 3 psi to 15 psi/4 mA to 20 mA transmitter using a Fluke 718Ex 30G Pressure Calibrator :

  1. Depressurize and isolate the transmitter. If opening the transmitter exposes voltages beyond the Instrinsic Safe (I.S.) rating use a continuous monitoring gas detector to monitor for explosive gases.
  2. Plumb the transmitter to the 1/8 inch NPT pressure port of the 718Ex. Connect the test leads per the figure above.
  3. Turn the calibrator on. Vent the calibrator and press zero to zero the pressure displayed. Close the vent control. 
  4. Press the UNITS key until PSI shows in the display.
  5. With the 718Ex’s bleed valve open to atmosphere, press the ZERO key. Close the bleed valve. Set the pressure / vacuum valve to +, for positive pressure.
  6. Use the hand pump to apply roughly 3 psi to the transmitter. Partial pump strokes will apply small increments of pressure. Use the fine-adjust knob to get reasonably close to 3.00 psi.
  7. Press the HOLD key, and record the psi and mA readings. Press the HOLD key to resume reading.
  8. Calculate and record the  error, using: Error = ([(i-4)/16] – [(P-3)/12]) * 100 where Error is in % of span, i is your measured current in mA and P is your measured pressure in psi.
  9. Repeat steps 5 through 7 at mid-range, around 9 psi, to check linearity at mid-span.
  10. Repeat steps 5 through 7, now at 15 psi, for a check at 100 % of span. 
If your calculated errors are within tolerance, the transmitter has passed your As-found test, and you are done. If necessary,perform your zero and span adjustments, then repeat steps 5 through 9 for an As-left test. Depressurize the line, and disconnect the 718Ex. Continue to monitor for explosive gas until the transmitter is returned to service and all non-I.S. voltagesor energy sources are isolated from exposure to the classified environment.

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