Test a thermistor

Having accurate temperature readouts is crucial for the success of many industrial applications. For many different manufacturing endeavors, machines need a certain temperature to function efficiently. There are many different devices on the market that measure temperature, but some are more accurate than others. Thermistors and RTDs are devices that measure precise temperatures. These tools are primarily used in applications that require accurate temperature read outs. Although these tools measure temperature, they operate differently and are suitable for different applications.

An RTD or a resistance temperature device measures resistance of 100 ohms at zero degrees. These devices are made with a thin strip of platinum on a plastic film. The RTD measures change in resistance in order to gauge temperature and measures temperatures up to 850 degrees Celsius. As temperature rises, so does resistance and an RTD gives this precise readout in digital form.     

RTDs are considered to be passive measurement devices that must be supplied with a current.  The voltage is read across the terminals and is easily translated into temperature via a simple algorithm. The electric current causes the RTD to self-heat, which ultimately damages the device. To limit this occurrence, it is best to limit the amount of currents as much as possible.

RTDs use a two wire or four wire methods in order to measure temperatures.

Thermistors are easily related to RTDs as they also gauge change temperature by measuring change in resistance. The main difference between the two is that thermistors are made out of metal oxide semiconductor material that is coated with a glass or an epoxy substance. Thermistors are able to measure both positive and negative temperature coefficients. A NTC, or negative temperature coefficient has a resistivity that declines when in the presence of rising temperatures. Conversely, a PTC, or positive temperature coefficient, has a resistivity that rises when temperature increases. Similar to the

RTD, a thermistor is also a passive measurement device that requires a consistent voltage. The voltage is read at terminals to acquire a temperature reading

In comparison, thermistors have a much higher sensitivity than RTDs and a higher overall nominal resistance. If you are interested in learning more about thermistors or resistance temperature devices, it is best to contact a local professional in the field. If you are looking to work with these devices, a manufacture of RTDS and thermistors is the best resource for information.

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