How to Calibrate a Pressure Switch Using the Fluke 729 Automatic Pressure Calibrator


In this video, we're going to take the Fluke 729 Automatic Pressure Calibrator and perform a pressure switch calibration.

You see we have the Fluke 729 with the jacks connected up to the contact points of the pressure switch as well as the pressure line connected.

Setting up a pressure switch calibration

Start out by venting the 729 and zeroing the pressure. Then we're going go in and select tasks. Option number two for the pressure switch is the one I'll be selecting.

In the setup, notice we can set the setpoint which is when the switch in this case will close, so, we've got that set for 10 PSI. We're going to set the tolerance to 2 PSI. Minimum dead band; that would be the minimum difference between the open and close. We'll set that at .5. Maximum dead band, let's go ahead and set that for 3. And again, max pressure, that will be set automatically, but we can change that if we want. In this case we'll leave maximum pressure at 17. And the switch type is normally open. So, that's complete, we've got the test set up.

Calibrator Settings

  • Setpoint: 10 PSI
  • Tolerance: 2 PSI
  • Minimum dead band: .5
  • Maximum dead band: 3
  • Maximum pressure: automatic @ 17
  • Switch type: Open

Press continue, and notice the screen reads 0 PSI, and we're going to run the auto test. Notice the set and reset on the screen.

Running the calibration

Run the auto test and it will bring pressure up to about 3 PSI. And then boost it up and add a slow rate to get that switch to close and record the set point.

Once the switch closes, you'll see a change in the switch from open to close and you'll see the set point show up on the screen. The next step you will see is the pressure will drop to find out where the reset is.

Both of these values are being recorded and we can be saved in the calibrator. Once both tests are complete, you will see the results. This is what gets documented:

  • Set at 10.5 PSI
  • Reset at about 9.5 PSI
  • Dead band about 1 PSI
  • With a .5 PSI setpoint error

And that's within specifications so it passes, and we're done.

Documenting the pressure switch calibration

In order to document and save the calibration you’ve just completed, you start by putting in the tag ID of the switch, a serial number again and of course you can use the user list to select the name of the tech that performed the test. Once you've completed entering information, press done.

If any values returned were out of spec, we could do some step up step-down tests using F2 and F3 to recheck once we have made adjustments to the switch. And then you would run the as-left test F1 to finish. But, since this was in spec, we've completed our test so you can press done. We've completed our tests of the pressure switch calibration.