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A Beginner’s Guide To NTC Thermistors

With over 20 year’s experience in the thermal controls industry, ATC Semitec is the country’s leading distributor of thermal components.  NTC Thermistors are a key part of our business and in this article we will attempt to explain in layman’s terms, firstly, what NTC Thermistors are; then secondly, suggest some possible uses.  If you then feel they may form part of the solution to your temperature sensor or thermal safety requirements, please contact us at ATC and we will be happy to further advise.

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What Are NTC Thermistors?

Thermistor is a compound word formed of “thermal” and “resistor”, while the acronym NTC denotes, specifically, a Negative Temperature Coefficient Thermistor (as compared to the alternative Positive Temperature Coefficient – the PTC).  Temperature sensitive, these are solid state sensors that, in effect, behave as electrical resistors.  Their benefits are many and varied.  For instance, they are widely available, easy to use and affordable, while also being very adaptable.  They are not usually the choice for measuring high temperatures, but with decent output voltages, they are very effective for simple temperature measurements, where they are incredibly accurate, especially at these lower temperatures.

Usually constructed in temperature-sensing ceramics, Thermistors feature a semi-conducting element, which is sintered (formed into a solid mass via heating) so that with even small changes in temperature, it can detect large shifts in resistance.  A small direct (DC) current passes through the Thermistor, so that the voltage drop can be measured.  NTC Thermistors are non-linear, so that resistance will decrease as the temperature increases. The standard temperature of the Thermistor is usually 25°C at zero-power resistance. The Resistance Ratio then detects the ratio of a thermistor at 125°C, to that standard temperature of 25°C. The temperature should never pass that highest value.

What Are NTC Thermistors Used For?

Broadly speaking, NTC Thermistors find applications in temperature control, temperature compensation and temperature measuring. Extremely accurate, and highly versatile, their utility finds them in a wide range of applications:

The car industry

Demand has been massive in the car industry, with manufacturers using around 20 NTC Thermistors in the average new car.  You will now find them as components in fuelling systems, safety, engine monitoring and cooling.  This has been especially key with changes to emissions regulations in modern cars.

Manufacturing and the wider industry

NTC Thermistor probes can be found throughout industry, in everything from chemical analysis equipment and plastic laminating, through to soldering, hot gluing, copier machines, photo processing and, naturally, safety and fire protection.  They can be found in science labs, with uses as varied as bathythermography to titration, spectrophotometry to bolometry.

From the Domestic…

If you feel none of this relates to you, or your domestic environment, you may be surprised to hear there are NTC Thermistors in the humble domestic burglar alarm, in your air con, oven, fire detectors… even your fridge.  If you have ever used a thermometer to take your child’s temperature, there will have been one in there, too.

… to the otherworldly

Beyond the domestic, commercial and transport spheres, NTC Thermistors have found their way into everything from medical to military to scientific applications, everywhere from missiles to oceanographic exploration.  They have even been used in spacecraft!

There are NTC Thermistors to suit every possible need, and at ATC Semitec we have the leading range of reliable, durable models built to survive high temperatures, for long periods of time. Built from a variety of quality materials, and available in a range of designs, and fully customisable, we have a Thermistor to suit ever possible requirement.  Simply contact us on 01606 871 680 and we will walk you through the options and find the right Thermistor solution for you.