How to test a sensor with a multimeter

ES Systems: Pressure transmitters are precise instruments, and they, like all instruments, can sometimes fail.

It’s difficult to tell whether a transmitter is working well or not, especially when on the field, and even if you know something is not right, it might still be difficult to know how to test a pressure sensor.

This is because, without specialized equipment, you won’t be able to see or interpret pressure increase in a container in most cases.

Do you want to know how to tell if a transducer is bad?

All you need is a multimeter!

What is a multimeter

In our case, a multimeter is the finest tool for determining if a transmitter is operating or not.

In general, it is a well-known measuring instrument among electricians and technicians in the electrical/electronic industries that can measure multiple electrical properties, such as voltage, current and resistance.

Multimeters can be either analog or digital, with digital multimeters (also commonly abbreviated as dmm) becoming more and more popular.

How to test a sensor with a multimeter

In order to test a pressure transducer, you need to connect the transmitter to the multimeter and use the suitable excitation voltage to excite the transmitter.

At zero load, measure the transmitter’s voltage output. Record the voltage and compare it to the manufacturer’s datasheet’s no-load voltage specification.

If the measured value does not correlate, the pressure transmitter is not working correctly.

If the transmitter’s output is current (4-20mA) you can simply connect a resistance (usually 250R) in series and measure the voltage across the resistance in order to determine if the sensor is malfunctioning.

How to check a pressure transducer before installation

It is critical to test the pressure transmitter prior to installation – it gives you the ability to identify any system flaws.

You’re more likely to acquire inaccurate pressure data if you use a malfunctioning pressure transmitter, which can lead to unfavorable results. Pressure transmitters should be tested at regular intervals to ensure that they are performing properly and within specifications.

Follow the steps mentioned below and learn how to check a transducer.

How to test a 2-wire current pressure sensor

• Connect the V+ terminal of the power supply to the V+ terminal of the transmitter
• Connect the V- (or GND) terminal of the transmitter to the V+ lead on the multimeter
• Connect V- (or GND) lead of the multimeter to the V- (or GND) terminal on the power supply

The transmitter must deliver a current range from 4 to 20mA in no-load conditions. The manufacturer’s datasheet usually specifies the exact values corresponding to various pressure measurements. Check the datasheet to see if the transmitter is working properly.

How to test a 3-wire current pressure sensor

• Connect the V+ terminal of the power supply to the V+ terminal of the transmitter
• Connect the V- (or GND) terminal of the transmitter to the V- lead of the power supply
• Connect V- (or GND) lead of the multimeter to the V- (or GND) terminal on the power supply
• Connect Iout lead of the transmitter to the I+ terminal of the multimeter

The transmitter must deliver a current range from 4 to 20mA in no-load conditions. The manufacturer’s datasheet usually specifies the exact values corresponding to various pressure measurements. Check the datasheet to see if the transmitter is working properly.

How to test a 3-wire voltage pressure transmitter

• Connect the V+ terminal of the power supply to the V+ terminal of the transmitter
• Connect V- (or GND) of the transmitter to the V- (or GND) terminal of the power supply
• Connect V+ leads of the multimeter to the Vout out terminal of the transmitter
• Connect V- (or GND) lead of multimeter to the V- (or GND) terminal of the power supply

The transmitter must provide a voltage that matches the manufacturer’s datasheet when no load is applied. If the results are identical, the pressure transmitter is working properly; if the values aren’t similar, your pressure transmitter is most likely malfunctioning.

How to test a 4-wire voltage pressure transmitter

• Connect V+ of the power supply to the transmitter’s V+ terminal
• Connect V- of the power supply to the transmitter’s V- terminal
• Connect V+ lead of the multimeter to the Vout+ lead of transmitter
• Connect V- lead of the multimeter to the Vout- lead of transmitter

In no-load condition, the transmitter must output a voltage equal to the no-load voltage specified in the datasheet.

As you can see, it’s easy to learn how to test a sensor with a multimeter, and this knowledge can be applied well beyond pressure sensors, and into speed sensors, oxygen sensors etc.

Make sure you carry a multimeter with you, especially when on the field, in order to tell if a transducer is bad and how to fix it!