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Pressure Transducer Training Project

Updated: Mar 30, 2023

This training project is designed to provide a clear way to see how a pressure transducer operates and how they can be tested.

Why does the Pressure Transducer Matter?

Pressure transducers are typically found on commercial VRF (variable refrigerant flow) systems. These devices are used to communicate the refrigerant pressure, as a specific voltage, to the PCB. This project is designed to visualize how pressure transducers work and provide an example for how to test them. To learn more about pressure transducers, watch this video: and to learn more about inverter mini splits, check out our book:

Building the Display

A pressure transducer testing assembly can be built in a number of ways, using a variety of different materials. For this example, the tools, parts, and steps are listed below:

Tools Required
  • Wire Cutter/Stripper

  • Multimeter

  • 1/4" Refrigerant Hose with Valve

  • Pressurization Method such as Nitrogen along with a Regulator

  • Quick Connect Pressure Test Gauge

  • 2 Adjustable Wrenches

Parts Required
Step #1

Before setting up the pressure transducer project, first determine the power source and ratings for the transducer. For this example, the transducer operates on 5 volts DC. In this case, either 3 AA batteries in a battery holder (4.5V to 4.95V) or a 5V USB phone charging cube and cord can be used. In the case of cube and cord, the end of the charging wire can be cut off and stripped back to reveal a black and red wire. Make sure the cord is unplugged and not powered when doing this.

Step #2

After choosing a power source, the three wires on the pressure transducer can be cut to the desired length. Be sure to leave at least 2" of wire connected to the transducer plug end.

Step #3

Next, using the pieces of wire cut off the transducer, cut a short length of wire (no shorter than 2") from each wire. Strip both ends of each wire. Strip the ends of the wire attached to the pressure transducer. Additionally, strip the ends of each wire from the power source (either the battery holder or the phone charging wire (while non-powered)). Wire nut each of the three wires as shown in the image below (all red wires together and all black wires together). Leave the green wire unattached.

Step #4

Next, attach the 1/4"flare union or 1/4" flare tee to the pressure transducer body. Attach the plug end into the transducer. If using a 1/4" flare union, be sure to snug the union to the pressure transducer body using the two adjustable wrenches.

Step #5

Make sure that the exposed wires coming from the wire nuts are not making contact with any conductive surfaces and that they remain separate from each other and separate from the green wire from the transducer. Now, the pressure transducer can be powered.

Step #6

The multimeter can now be used to measure the voltage. In order to measure voltage on the pressure transducer, connect one probe to the exposed black wire and one probe to the exposed green wire. Then turn on the multimeter and set it to measure DC Volts. Turn the power supply on at the on/off switch on the side of the battery case. In the case of a phone charging cord allow power to the cord to supply 5V to the pressure transducer. This will power the internal circuit board within the pressure transducer. When pressure is not being applied, a millivolt measurement should be present.

Step #7

After the multimeter has been set in place, the pressure source can be connected. If using a nitrogen tank and regulator, a 1/4" hose can be run from the nitrogen regulator to the 1/4" flare union or tee. If using a 1/4" flare tee, a pressure gauge can also be mounted onto the tee, allowing the user to view the pressure more accurately.

Step #8

While wearing appropriate PPE (personal Protective Equipment), apply nitrogen pressure a little at a time in 50PSI increments. Make sure to not exceed the pressure rating on the pressure transducer. As pressure is applied, the voltage measured by the multimeter will increase.

Make sure that pressure does not remain in the pressure transducer tubing or downstream of the nitrogen regulator when not in use. Also make sure to shut the nitrogen tank handle to the closed position after use.

Using the Project

At this point, the pressure transducer should be ready to use for testing! Testing the pressure transducer using this setup will allow the user to see the relationship between the pressure and the voltage present on the green output wire of the pressure transducer. On a VRF system, the PCB (Printed Circuit Board) powers the pressure transducer and interprets the output voltage to mean that the system is running at a certain pressure at the pressure transducer's mounted location.

Alternative Method for Testing

Alternatively, the pressure transducer's brass port section can be cut apart to access the internal sensor. This method would allow for pressure to be applied using fingers to push on the end of the sensor. If cutting the brass section apart, make sure to wear proper PPE and verify that the pressure transducer is disconnected from the HVACR system and no gas pressure is present.

If you are interested in learning more about pressure transducers, these projects, and how they can be used for instruction, be sure to check out the video below. If you are interested in learning more about inverter mini split operation and testing purchase our new Inverter Mini Split Operation and Service Procedure book, available in our store!

If you want to know more about Inverter Mini Splits, check out our Book!

Published: 3/29/2023

Author: Brandon Price

About the Author: Brandon is the Director of Production at AC Service Tech LLC and has contributed to the creation of various resources. Brandon has several years of experience as an HVAC installation and service technician and has worked under Craig as an apprentice. Brandon is also the primary project manager as well as web designer and illustrator at AC Service Tech.



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