PM600 and PM630 Pressure Measurement Modules model A28M (28 MPa or 4000 psi) or higher automatically correct the drift of their quartz sensor by adjusting them to match the value of the module's on-board barometer (AutoZero process). This is only done when in absolute mode and the pressure controller is vented and in a ready state. Note that on factory calibration reports for modules A28M and higher that the on-board barometer is calibrated with data and coefficients reported. Because of this, it is required to calibrate the on-board barometer each time the module is calibrated. This article provides instructions to calibrate and/or adjust the on-board barometer.
Note: This article only applies to PM600 and PM630 Pressure Measurement Modules. PM200, PM230 and PM500 modules do not have on-board barometers or fast sensors. This article can be used to calibrate or adjust the on-board barometer of PM600 modules A20M and below (20 MPa or 3000 psi) but this is not necessary to maintain or achieve the uncertainty specifications of the modules.
Use any available standard (controller) that can source pressure in the range of 10-16 psia to run the calibration. Make sure the uncertainty specification of the controller is ±0.01 psi or better. Connect the TEST port of controller to the reference port of the calibration sled and connect the EXHAUST port of the controller to a vacuum pump.
1. Install the PMM in the calibration sled
2. Set the unit of the pressure to kPa or psi. To set the unit of measure send "PRES_UNIT KPAL" for kPa or "PRES_UNIT PSI" for psi. Only send the part of the command that is inside the quotation marks. Do not send the quotation marks.
3. Capture the as Found calibration coefficients for the on-board barometer C0 and C1 by sending the following commands. Only send the part inside the quotation marks.
"OFFSET_SET2?” (reply is in psi)
"C1=GAIN_SET2?” (unitless)
"CAL-DATE2?”
4. Apply at least three pressure points (10,13 and 16 psi). When the pressure is stable and ready, query the on-board barometer pressure by sending the RS232 command “VAL2?"
5. Record the reference pressure and PMM on-board barometer values in the attached Excel workbook
6. If the PMM on-board barometer is in tolerance you are done.
7. If the PMM on-board barometer is out of tolerance, or you wish to adjust it, first set the PMM on-board barometer calibration coefficients to factory default values. Clear C0 and C1 by sending the following commands. Don't send the quotation marks.
"C0=OFFSET_SET2 0”
"C1=GAIN_SET2 1”
“CAL_STORE” (save the changes)
8. Repeat steps 4 and 5 and record the new pressure points in the Excel sheet to calculate the new C0 and C1. Once you have the new coefficients, send the following commands. Only send the part inside the quotation marks.
"C0=OFFSET_SET2” (New calculated value in psi)
"C1=GAIN_SET2” (New calculated value)
"CAL-DATE2 MM/DD/YY” (use today's date for MM/DD/YY"
“CAL_STORE” (save the changes)
9. Repeat steps 4 and 5 to verify the adjustment.
10. Remove the module from the calibration sled and install it back in the pressure controller that it is used with. Go to the following menu path to verify the new coefficients. Setup > Module Information > (choose the slot) > Calibration Coefficients > (enter 8270, 8370 or 1234). Note that this screen may not show the full resolution of the values.
When the module is installed in a pressure controller, the command to read the on-board barometer is below, where x is the slot number; slot 1=2, slot 2=12, slot3=22, slot4=32, slot 5=42.
meas:presx?
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