How To Use A Multimeter To Troubleshoot Your Sensor

Video How to check parking sensors with a multimeterSo you are having a problem with the signal from your sensor. Maybe it only works sometimes, maybe there’s too much noise to establish a strong connection, or maybe you just don’t know what’s wrong. An easy way to find out what’s wrong is to use a multimeter to test your sensor. Don’t worry, we will teach you how to use a multimeter to troubleshoot your industrial sensor and get it working properly in no time! But wait – what is a multimeter and how does it work? Let’s take a quick look. After all, we’ve got a sensor for troubleshooting Read: how to test parking sensors with a multimeterWant to get straight into troubleshooting? Don’t worry, click here for our simple steps on how to use a multimeter to troubleshoot your sensors!

What is a multimeter?


A multimeter is an electrical instrument used to test electrical circuits. Multimeters can measure voltage, current, resistance, and continuity, hence the name: multimeter. A multimeter is very important for troubleshooting. When a circuit or device malfunctions, continuity testing (i.e. circuit with continuity from source to sensor and vice versa) and voltage/current/resistance measurement can help identify and determine trouble. On a multimeter, you will find several settings available to test. Different areas. The most common settings are:

  • for current, both alternating current (AC) and direct (DC), measuring from micro or milli-amps to amps;
  • for voltages, both AC and DC, measured from millivolts to hundreds of volts;
  • for resistance, measure from ohms to megaohms.

More advanced models have additional settings for measuring capacitance, decibels, frequency, inductance, and/or temperature.

How does a multimeter work?

Magic miniature elves. Or not. We were unable to reach them for comment. (I know, there’s nowhere more fun than elves.) Ohm’s law states the fixed relationship between voltage, current, and resistance between any two points in a circuit: I = V/R (i.e. current by voltage divided by Resistance). Like any good math student, most use two known quantities to solve for a third, unknown, quantity:

  • To measure resistance, one measures the change in voltage produced by a small current.
  • To measure voltage, one measures the motion produced by a small quantifiable current through a known resistance.
  • To measure current, an analog motion is measured through a resistor at a specific ratio to the current in question.
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The other quantities mentioned above (capacitance, etc.) are measured using the same techniques.

Step by Step Guide to Testing Multimeters

Thus, you have a multimeter in hand. So what now? Let’s run three simple tests that will help us identify the problem. Use the diagram below for reference as you move through the tests.sample circuit for multimeter test connections

Multimeter Test: Continuity

We’ll start with a multimeter continuity test. We want to make sure that all wires are connected correctly.Step 1Read more: how to clear a rewritable cd Disconnect the wire for the sensor at its power source (Point A in the diagram).Step 2 Plug it in. black probe into COM (usually) on your multimeter. Plug the red probe into the VΩ port.Step 3 Set your multimeter to Continuous – the icon looks like this: •))). Step 4 Connect the red probe to the + wire of the sensor and connect the black probe to the ground wire going to the sensor. Note: Communication wiring is often more complicated than + and – wires and will vary depending on the output of your sensor and control system. Please refer to your sensor’s user manual or manufacturer for more information. If the multimeter doesn’t take a reading, then something is wrong with the wiring. Repeat these steps along different parts of the circuit between the source and the sensor to isolate the fault. Step 6 This process is also possible (and recommended!) with the sensor’s communication wiring.

Multimeter test: Voltage

After establishing circuit continuity, check the mains voltage, but not the source.Step 1 Reconnect the sensor’s power supply. Step 2: Disconnect the power cord at the sensor (Point C in the diagram) or the connection point closest to the sensor (Point B, if the cable to your sensor cannot be disconnected at the sensor). Step 3: Retain same probe – multimeter connections.Step 4 Connect red probe to input + wire, pin or terminal and black probe to ground wire /pin/ terminal.Step 5Choose the closest DCV value on the multimeter, but greater than the mains voltage.Step 6Read more: how to make a ponytail with a ribbon Turn on the power. Step 7 Verify that the voltage at the sensor is within the range recommended in your manual. If so, we’ve eliminated the source voltage as the problem. If not, the voltage source is at least a problem, if not a problem. (And either way, turn the power back off!)

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Multimeter test: Resistance

Next, we will test the impedance or resistance of the circuit *. In general, the impedance of the circuit is only important for communication circuits (Modbus, Hart, etc.), but testing can still be effective for other circuits. (Point A).Step 3M Repaint the same probe – multimeter connections.Step 4 As before, connect the red probe to the + wire going to the sensor and connect the black probe to the wire earth goes to the sensor. Step 5 Many sensors use communication protocols that require a minimum of 150Ω to 180Ω, so choose the Ohm value on the multimeter closest to, but greater than, 200Ω. If the impedance of the circuit is less than that recommended by your manual, add an appropriate amount of resistance to the circuit. Step 6 If the multimeter does not register impedance, select the next highest Ohms value. If the impedance of the circuit is too high (and not infinite), something will need to be removed from the circuit (switching to a smaller wire size, too many intermediate junctions, etc.).

Is your sensor still not working?

If these steps don’t help you identify and isolate the problem, there’s a good chance your sensor has a problem. If you’re in need of a new sensor, check out our selection of high-quality sensors. We make sure all of our products are reliable and always ready to help our customers. You can email us directly or submit a contact form and one of our representatives will get back to you within 24 hours! * Yes, I know that there is a difference between impedance and resistance (X = R + jωL). However, I also know that the difference is only important for AC circuits at high frequencies. But even for this DC circuit, the total opposition to current is called impedance rather than resistance. Explore APGtop photo credit: Andrew Mason via flickr ccRead more: How to clean a Window Air Conditioner without removing it

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