HART Smart Pressure Transmitter Calibration
Pressure transmitter manufacturers have improved the accuracy and technology of smart pressure measurement devices. As a result, many conventional calibration tools have become inadequate or simply unable to test and calibrate these high accuracy pressure transmitters. Better test solutions are required.
Verifying and documenting the performance of a HART communicator-enabled pressure transmitter can require a bucket full of tools. Performing pressure transmitter calibration with a HART-enabled calibrator like the Fluke 754 Documenting Process Calibrator with HART Communication simplifies the task and reduces what you need to carry.
Before going to the field, install the pressure module adapter to the hand pump with thread seal. Once you’ve properly installed the adapter on the pump, changing modules to different pressure ranges is a snap, no tools required.
To get the accuracy needed to test these new high accuracy transmitters, match the pressure measurement standard range closely to the device tested. For example, use a 100-psi pressure module to calibrate and test a transmitter ranged at 100 psi. Industry standards suggest the measurement standard should be 4-10 times more accurate than the device being tested, so best-in-class accuracy is required.
The Fluke 750P Series Pressure Module has the HART communication functionality built in to enable smart trims on transmitters. It can also document transmitter performance before and after adjustment and calculate pass/fail errors.
How To Perform Pressure Transmitter Calibration
- Isolate the transmitter from the process being measured and its loop wiring. If measuring the mA signal across the transmitter test diode leave the wires intact but note this method does not give the best mA measurement accuracy.
- Connect the mA measurement jacks of the 754 to the transmitter.
- Connect the pressure module cable to the 754 and connect the transmitter test hose from the hand pump to the transmitter.
- Press the HART button on the calibrator to see the configuration of the transmitter.
- Press HART again and the calibrator will offer the correct measure/source combination for the test. If documenting the calibration press As Found, input the test tolerance, and follow the prompts. If the measured mA signal at the test points is found within tolerance, the test is complete. If not, adjustment is required.
- Select, adjust, and trim the pressure zero, mA output signal and input sensor.
- After adjustment select As-Left, document the condition of the transmitter and after adjustment and if the test passes, pressure transmitter calibration is complete.
FAQ
Why Is Pressure Transmitter Calibration Important?
Regular calibration ensures transmitters measure as accurately as possible. This helps prevent measurement discrepancies.
Can Pressure Transmitter Calibration Be Done in the Field?
Yes, pressure transmitter calibration can be done in the field. However, a calibration laboratory offers calibration in a controlled environment, providing a greater degree of accuracy.
How Often Is Pressure Calibration Necessary?
Every facility has its own way of determining how often pressure transmitter calibration is necessary. Factors to consider include performance history, regulatory compliance, as well as safety, quality, and preventive maintenance.
How Do You Decide on a Calibration Accuracy Target?
It’s important to strive for a calibration target that is accurate but not impossible for teams to strive for. Setting a maximum permissible error (MPE) that is overly strict can cause problems — in some cases, pressure transmitter calibration may not even be possible with standard lab equipment. A reasonable MPE that’s within reach is the smart choice. Just be sure the reference equipment is at least three times more accurate than the pressure transmitter you are calibrating.
Where Should Calibration Be Performed?
Select a highly stable environment to perform your pressure transmitter calibration. This is because factors like temperature and humidity can influence the pressure reference and the pressure transmitter too.