A thermistor, whose name comes from ‘thermal’ and ‘resistor,’ is a type of resistor whose resistance depends on temperature. For all intents and purposes, a thermistor is a resistance thermometer. They are made from metallic oxide formed into a bead, disk, or cylindrical shape enclosed in epoxy or glass. While they do not work well at extreme temperatures, thermistors are ideal for measuring temperatures at a certain point and are most precise when used within a limited range. The range in which a thermistor will work is dependent on the base resistance.
Thermistors are simple to use, comparatively cheap, and highly durable. They have many uses, in applications such as digital thermometers, in vehicles to measure oil and coolant temperatures, in household appliances like ovens and refrigerators, and other applications that require heating or cooling protection microcircuits for safe operation. Thermistors are sometimes built into devices used in more complex applications such as laser stabilisation detectors, optical blocks, and charge-coupled devices.
There are two types of thermistors: Negative Temperature Coefficient (NTC) thermistors and Positive Temperature Coefficient (PTC) thermistors. In an NTC, the more common of the two, the thermistor’s resistance decreases as the temperature increases and vice versa. In the PTC, the resistance increases as the temperature increases, and vice versa. Thermistors of this type are commonly used as a fuse. The resistance change of a thermistor, which changes with temperature, is dictated by the type of material used. Thermistors are nonlinear, meaning the connection between resistance and temperature will not form a straight line on a graph, but instead will form a curve.
Another type of temperature sensor that offers a similar function to thermistors is the resistance temperature detector (RTD). Both thermistors and RTDs offer their own advantages and disadvantages, and the intended application will determine which sensor is most ideal. The advantages of thermistors are their durability, sensitivity, compact size, and their relative affordability. Their disadvantages include their curved output and limited temperature range. RTDs, on the other hand, offer the benefits of being extremely accurate, providing a linear output, and measuring a wider temperature range. The drawbacks of these are their slow response time and high cost.
There are also a variety of shapes of thermistors available for surface mounting or embedding. The shape is dependent on the type of material being monitored, such as solid, liquid, or gas. Depending on the application, the thermistor can be enclosed in resin or glass, baked on phenolic, or painted over. For instance, some types of thermistors are mounted onto circuit boards while bead thermistors are embedded directly into the device. Whatever the application, maximum surface contact with the device being measured is ideal.
In summary, thermistors are temperature-dependent resistors that change resistance as temperature chances. They are tailored to situations where a specific temperature needs to be maintained, and are sensitive to minute temperature changes. Thermistors are the best way to measure and control the temperature of a thermo-electric cooler, but can do much more than that. No matter the intended application, be sure you are getting thermistors from a trusted and reputable source.
For all types of thermistors and much more, look no further than ASAP Parts Online, a trusted supplier of parts for a wide range of industries. Owned and operated by ASAP Semiconductor, we are an online distributor of aircraft parts as well as parts pertaining to the aerospace, civil aviation, defense, electronics, and IT hardware markets. We’re always available and ready to help you find all the parts and equipment you need, 24/7-365. For a quick and competitive quote, call us at 1-702-919-1616 or email us at firstname.lastname@example.org.
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