How to Check a PT100 with a Multimeter

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You will find many different types of sensors on the market—humidity sensors, pressure sensors, temperature sensors, flow sensors, proximity sensors, RTD sensors, and so much more. PT100 is a type of resistance temperature sensor that is made using a platinum element along with a resistance of 100 ohms at 0 degrees Celsius and normally with a 38.5-ohm fundamental interval. 

A resistance temperature sensor (RTD) is a sensor utilized to measure temperature. They are made from nickel, copper, and platinum and have a repeatable temperature versus resistance relationships as well as an operating temperature range of -200 degrees Celsius to +850 degrees Celsius. 

For many years, they have been widely utilized to calculate the temperature in industrial and laboratory processes and have established a reputation for stability, repeatability, and accuracy. Platinum is considered a noble material and provides the most reliable resistance-temperature relationship over the biggest temperature range. Hence, it’s more typical than nickel and copper RTDs.

What is PT100? 

PT100 is one of the most accurate and highly sought RTD sensors. It does not just offer excellent accuracy, but it also offers superior repeatability and stability. PT100 sensors are also immune to electrical noise. Thus, it’s well fitted for temperature measurement within environmental settings, particularly generators, motors, and other high voltage equipment. 

It’s worth mentioning that they are slowly changing thermocouples in industrial applications under 600 degrees Celsius. That’s mainly because of the RTD’s better accuracy and repeatability. 

Resistive sensors are utilized to measure numerous physical parameters like displacement and position, human interface devices, force, and so much more. Temperature sensors like RTD and PT100 can be damaged because of electrical overstress, abuse, or normal wear and tear. Digital multimeters can measure resistance correctly with a wide enough range Ω to GΩ.

Some digital multimeters can also measure capacitance that can help fix a broad spectrum of capacitive sensors. 

How Does It Work?

As stated, the PT100 sensor is a common example of a resistance temperature detector. It’s mainly based on the concept observed in metals where a change in temperature would cause a change in the material’s resistance. 

Platinum shows a positive temperature coefficient. Meaning it shows an accelerating resistance with accelerating temperature. That’s why it’s the most typical material utilized to create RTDs. 

The PT100 sensors are created to have a resistance of 100Ω at 0.0 degrees Celsius, and a resistance increase of 0.385 Ω per 1-degree Celsius increase between 0 and 100 degrees Celsius, according to ISO 60751: 2008. 

These sensors are typically constructed with two methods:

  1. Thin Film Sensors

These sensors are based on a ceramic substrate with a deposition of high purity platinum, laser-etched. That is then closed within a glass adhesive. Such sensors are more reasonable compared to wire-wound detectors and are less sensitive to impact damage. Nevertheless, they work in a smaller temperature range. 

  1. Wire Wound Sensors

Platinum wire wound sensors are composed of a small platinum wire roughly closed around or looped in a ceramic core. These sensors can be utilized over a broad spectrum of temperatures. Yet, they can be prone to mechanical shocks that encourage measurement drift. 

Choosing the Perfect PT100 Detector

Remember that this is a balance between competing factors. For instance, choosing a PT100 sensor for use in a pharmaceutical autoclave chamber. That’s a balance between the resilience of the sensor to recurrent handling by process operators and the optimum tolerance of the temperature measurement.

Therefore, a class A thin film sensor would be most suitable for pharmaceutical uses. 

On the other hand, a class B will have enough tolerance for the majority of manufacturing and chemical uses.

Keep in mind that maximum service temperature might also indicate a ceramic detector in preference to a thin film sensor. 

Should You Use PT100? 

You will find many good things using RTDs (PT100 and PT1000). Some of its advantages are as follows:

  • Most stable and accurate over time (especially when compared to thermistors and thermocouples)
  • Platinum PT100 are ideal for higher temperature ranges
  • Long-term stability
  • Present exact measurement even in extreme circumstances
  • Consistent
  • High repeatability
  • Highly accurate

Standard response times of PT100 are between 0.5 to five seconds, which isn’t categorized as an immediate response. 

However, most applications won’t necessarily need an immediate response. 

That makes PT100 the best option. 

Many suitable industries for PT100 temperature sensors include HVAC, marine, white goods, automotive, and other industrial applications. 

How Do You Test a PT100 with a Digital Multimeter?

Here are the steps you need to follow if you like to test your PT100 temperature sensor with a digital multimeter. You can use a very simple multimeter for this process. 

  1. Place your digital multimeter on the resistance measurement 
  1. Calculate the resistance among the individual couple of wires. You must get a reading close to 100 in two couples and zero in one couple. 
  1. If you get a reading close to 100 in two couples, then you understand your PT100 temperature sensors and the wires are doing well. 
  1. The couple you read, zero is a couple of wires on the same side of the resistor. Most of the time, their color will be red, the other side is often white in color 
  1. You may be wondering why you need two wires on the same side. Keep in mind that the PT100 is a resistor that changes its resistance as dependents on the temperature. However, the wires have some resistance as well. When you connect your PT100 sensor to a controller or a transmitter, the device measures the resistance of the wires. It ignores them while calculating the PT100. 

That way, you have a more exact and specific reading.

Final Thoughts 

There you have it! Now you understand how to test a PT100 temperature sensor and how to locate what each wire is. Thank you so much for reading. Are you now ready to test your PT100 with a digital multimeter? 

We hope you find something useful in today’s post. Share your thoughts with us by leaving your comments below.

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