How to test a temperature sensor with a multimeter?

In this blog post, I will show you how to test a temperature sensor with a multimeter. Temperature sensors are used in a variety of applications, including HVAC systems, automotive engines, and many other types of equipment. It is important to test the accuracy of your temperature sensor to ensure that it is providing accurate readings. Here, I will tell you how use a digital multimeter to test temperature sensors. But first let see what is a temperature sensor and how it works.

What is a temperature sensor and what does it do?

A temperature sensor is a device that measures the ambient temperature. It can be used to monitor the environment, or it can be used in conjunction with other devices to control a process. For example, in an HVAC system, a temperature sensor can be used to detect when the room has reached the desired temperature and then signal the heating or cooling system to turn off. In industrial applications, the most commonly used temperature sensors are thermocouples, RTD and PT100.

How does a temperature sensor work?

A temperature sensor typically consists of two parts: a sensing element and a signal conditioner. The sensing element is usually made of metal or semiconductor material, such as silicon. When the ambient temperature changes, the resistance of the sensing element also changes. This change in resistance is converted into a change in voltage or current by the signal conditioner, which is then outputted as an analog or digital signal. 

Type of Temperature Sensors

There are three main types of temperature sensors: resistance temperature detectors (RTD), thermocouples, and silicon diodes.

Resistance Temperature Detectors (RTD): 

RTDs are made of a metal wire or ribbon that has been wound into a coil. The resistance of the metal changes with temperature, so by measuring the voltage across the RTD, you can determine the ambient temperature. Moreover, the most common type of RTD is the platinum RTD, which has a resistance that changes linearly with temperature.

Thermocouples: 

A thermocouple is made up of two dissimilar metals joined together at one end. When the junction of these two metals is heated, a voltage is generated. The magnitude of this voltage reading depends on the type of metals used and the temperature of the junction. Thermocouples are often used in high-temperature applications because they can withstand very high temperatures. There are different type of thermocouples, so I have made a separate guide about testing thermocouples.

Silicon Diodes: 

A silicon diode is made up of a piece of silicon that has been doped with impurities to create a P-N junction. When the diode is exposed to heat, the resistance of the silicon changes. By measuring this change in resistance, you can determine the ambient temperature. Silicon diodes are often used in low-temperature applications because they are very sensitive to small changes in temperature.

The most common way to test a temperature sensor is by measuring the change in resistance as the ambient temperature changes. You can do this using a digital multimeter with an ohmmeter function. Set the

Now that we know what a temperature sensor is and how it works, let's see how to test it with a multimeter. 

How to test a temperature sensor with a multimeter in 3 easy steps:

industrial temperature gauges
Step 1:

First of all you need a multimeter. It can be analog or digital, but i prefer digital multimeters. Now, Turn it on and set the dial to resistance. Moreover, make sure that the test leads are inserted in the slots properly. Red Test lead in (V) and black test lead in the (Com).

Step 2:

Now, take the temperature sensor and connect it in between the red test lead and black test lead.

Step 3:

Now, slowly increase the temperature of the sensor by heating it with a lighter or using a heat gun. You will see the resistance on the multimeter changing as you increase the temperature.

You can also use a silicon diode to test the temperature sensor. Just connect it in between the red and black test leads. The resistance of the silicon diode will change as the temperature changes.

By using a multimeter, you can easily test a temperature sensor and see if it is working properly. 

How to test temperature sensor of your car or truck?

There are a few ways to test vehicle's temperature sensor with multimeter. The most common way is to locate the sensor and measure the resistance between it and ground. Another way is to measure the voltage at the sensor. There might be heavy chances that your car control unit is faulty. Do check them also.

Wire Tracing

The easiest way to find the temperature sensor is to look for a two-wire connector with a yellow or orange wire. The connector usually has a label that says "temperature." The sensor is located on the intake manifold, near the firewall.

Standard measurement range

If you can't find the electrical connector or if the sensor is buried deep inside the engine temperature box. A temperature sensor is also in the intake plenum of engine. You'll have to measure the resistance between the two wires coming from engine. Therefore, measurement should be taken at room temperature (about 20 degrees C). The resistance should be about 1000 ohms.

Multimeter connections

If you're measuring the voltage, connect the positive lead of the multimeter to the wire that goes to the engine computer (usually a white wire with a black stripe). Connect the negative lead of the multimeter to ground. The voltage should be about 0.45 volts at room temperature. So, if the voltage is outside of this range, the sensor may be bad.

If you're not sure which wire is the positive and negative lead, try measuring the resistance between each wire and ground. The reading should be about the same for both wires. If it's not, one of the wires is probably reversed.

Use of scan tool

You can also use a scan tool to test the sensor. The scan tool will show you the voltage or resistance of the sensor. It will also show you the temperature that the sensor is reading.

engine testing with temperature scan tool

Testing automotive temperature sensor can be done with multimeter easily and it is a helpful way to locate problems in your car or truck. With this guide, testing temperature sensor should be a breeze.

Now that we know how to test a temperature sensor with a multimeter, let's see how to calibrate it. In addition to this, if you don't have a multimeter yet then you can check my life of best multimeter for electronics technicians

7 Common problems with temperature sensors and how to fix the:

Sensor is dirty or contaminated:

If the sensor is dirty or contaminated, it will not give accurate results. Clean the sensor with a clean cloth and try testing it again.

Sensor is broken:

If the sensor is broken, you will see a constant reading on the multimeter, even when the temperature changes. You can easily assess its condition by sensor's body. If there is any break just replace the sensor with a new one. If there is any temperature always make sure that it is in good condition.

Coolant temperature sensor is defective:

If the sensor is defective, you will see erratic readings on the multimeter, even when the temperature doesn't change. Replace the sensor with a new one.

Leads are not connected properly:

If the leads are not connected properly, you will get inaccurate readings on the multimeter. Furthermore, make sure that the test leads are inserted in the slots properly.

Meter is not set to resistance:

If the meter is not set to resistance, you will get inaccurate readings on the multimeter. Make sure that the dial is set to resistance and try testing it again.

Ambient temperature is too high or too low:

If the ambient temperature is too high or too low, you will get inaccurate readings on the multimeter. Try testing the sensor in a different environment or check the wires, there must be a leakage.

Calibration is not correct:

If the calibration is not correct, you will get inaccurate readings on the multimeter. calibrate the meter according to the instructions in the manual and try testing it again. You can do this negative temperature coefficient measurement.

These are the most common problems that you will face while testing a temperature sensor with a multimeter. By following the instructions given above, you can easily test and calibrate a temperature sensor. 

How to calibrate a temperature sensor with a multimeter?

A faulty temperature sensor not only damage the equipment or your car but can also put your life into danger. Mostly cars upper radiator hose or coolant sensor malfunctioned, which can cause complete engine failure.

The first step is to find the resistance of the sensor at a known temperature. This can be done by using a table of values or by measuring the resistance with a multimeter.

Next, you need to determine the actual temperature of the sensor. This can be done by using a thermometer or by measuring the voltage across the sensor.

Finally, you need to compare the resistance of the sensor at the known temperature with the actual temperature of the sensor. If they are not equal, then you need to adjust the calibration constant until they are equal.

By following these steps, you can easily calibrate a temperature sensor with a multimeter.

Tips for keeping your temperature sensor working properly:

Clean the sensor regularly:

If the sensor is dirty or contaminated, it will not give you actual temperature. Clean the sensor with a clean cloth and try testing it again.

Keep the wires away from heat:

If the wires are exposed to heat, they will get hot and distort the readings on the multimeter. Keep them away from heat sources.

Check the calibration regularly:

If the calibration is not correct, you will get inaccurate readings on the multimeter. Check the calibration regularly and adjust it if necessary.

Replace the batteries regularly:

If the batteries are weak, they will not be able to power the sensor properly and you will get inaccurate readings. Replace the batteries regularly.

Keep the sensor away from strong magnetic fields:

If the sensor is exposed to a strong magnetic field, it will not work properly. Keep it away from magnets and other sources of electromagnetic radiation.

Handle the sensor carefully:

If the sensor is dropped or mishandled, it will break and you will have to replace it. Handle the sensor carefully. If there is a thermostat then check thermostat housing first.

Store the sensor in a safe place for accurate temperature reading:

If you are not using the sensor, store it in a safe place where it will not get damaged. Store it in a cool, dry place.

These are some tips that will help you keep your temperature sensor working properly. By following these tips, you can ensure accurate readings from your sensor.

5 Multimeters Recommended for testing temperature

1. Fluke 116 HVAC Multimeter

Fluke 116 is a choice of professional HVAC technicians. It has a LED display backlight which makes it easy to read in low light conditions. This meter has a built in thermometer so you can take temperature readings without having to carry an extra instrument. The microamps mode allows you to test flame sensors, and the LoZ mode prevents false readings. You can also check Resistance, continuity, frequency and capacitance with this multimeter easily.

fluke 116 hvac multimeter

4.8/5 stars with 367 Reviews

2. Klein Tools ET600 Multimeter

This Klein Tools multimeter is perfect for electricians, contractors, and home DIYers. With a resistance up to 4000M ohms, it can measure up to 1000V AC/DC, resistance, and continuity. The True Root Mean Square (TRMS) technology ensures increased accuracy, while the bar graph and Auto-power off features make it easy to use. The low battery indicator lets you know when it's time to replace the battery, and the fuse is easily replaceable. you can also check your car solenoid with it. For a guide you can check my solenoid testing blog.

 Klein Tools ET600 Multimeter

4.7/5 stars with 553 Reviews

3. Amprobe AM-570 Industrial Digital Multimeter

This is a hand-held digital multimeter with a flashlight. It can be used to measure voltage, current, resistance, frequency and capacitance. The meter has true RMS detection for accurate measurements of non-sinusoidal waveforms such as those produced by motors and generators. The low Z measurement capability makes it possible to detect stray voltages in electrical systems. A duty cycle measurement function allows the user to determine the percentage of time that an output is active during each cycle of a repetitive waveform.

The AM-570 also features temperature measurement (-22°F to +572°F), capacitance measurement (0.001 to 100000μF), and an auto power off function.

 Amprobe AM-570 Industrial Digital Multimeter with True-RMS

4.6/5 stars with 349 Reviews

4. Klein Tools MM700 Multimeter

This is a hand-held digital multimeter with a large, easy-to-read LCD display. It can be used to measure voltage, current, resistance, frequency and capacitance. The meter has true RMS detection for accurate measurements of non-sinusoidal waveforms such as those produced by motors and generators. You can measure up to 1000V AC/DC voltage, 10A AC/DC current and 40MOhms resistance. Plus, it has a CAT IV 600V Safety Rating and is built to withstand a 6.6-foot (2m) drop. The Klein Tools MM700 is also durable enough to withstand daily wear and tear on the job site. Klein also offers a budget friendly range of multimeter Klein mm600. You can check my blog about Klein mm700 vs mm600 to make your final decision.

 Klein Tools MM700 Multimeter,

4.7/5 stars with 490 Reviews

5. AstroAI Digital Multimeter 10000 Counts

AstroAI smart multimeter is a multifunctional and intelligent digital multimeter with 10000 counts display. It has a high-resolution color screen, and can automatically identify voltage, resistance, continuity and diode test. The smart mode of the meter can accurately measure voltage (V), current (I), resistance (Ω), frequency (Hz), duty cycle (%), and capacitance. With its high accuracy, it is suitable for electronic circuit. The operating temperature range of this sturdy electrical teste is up to 50℃. With it high temperature gauge you can measure hot and cold readings from -40℃ to 300℃.

AstroAI Digital Multimeter 10000 Counts

4.6/5 stars with 289 Reviews

Conclusion

All in all, properly calibrating and maintaining your temperature sensors is key to keeping your equipment or car running smoothly. By following the steps I outlined above, you can test and calibrate any temperature sensor in no time. Have any questions or comments? Let us know in the comments below! If you looking for best automotive multimeters then you can visit my blog. 

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