A derivative of the term thermally sensitive resistor, thermistor probes are highly precise, economical devices that take measurements of temperatures and liquid levels in a wide range of industries. Many everyday applications rely on these probes, including computing technology, vehicles, and consumer appliances.
Thermistor probes from Digital Instruments are extremely versatile and offer heightened sensitivity and quick response times for applications in a broad range of industries. All of our devices come pre-certified to allow for immediate use and enhanced temperature measurement technology.
What Is a Thermistor Probe?
Thermistor probes are resistance thermometers that depend on the temperature to determine their level of resistance. These devices are constructed out of metallic oxide to form a disk, bead, or cylinder that’s enclosed within glass or epoxy.
Thermistors can’t function in extremely high or low temperatures. However, they provide precise measurements in environments within a certain range of a target temperature. This range is determined by its base resistance and is typically very accurate within about 50°C in either direction of the target temperature.
Thermistors are durable, inexpensive, and easy to use for a variety of applications. Unlike conventional thermometers, thermistors do not display a temperature reading, rather their resistance level fluctuates with changes in temperature.
Thermistor Types & Configurations
Depending on the needs of a particular application, different types and configurations of thermistors are available, including:
Negative Temperature Coefficient (NTC)
NTC thermistors are the most commonly used thermistor device. In NTC thermistors, resistance has a converse relationship with temperature. Resistance decreases with increases in temperature and increases when temperature decreases. Industries that commonly use these thermistors include product manufacturing, HVAC, appliance, and transportation. Corrections can be applied to maintain accurate measurements if the thermistor is to operate in an environment with extremely high temperatures.
Positive Temperature Coefficient (PTC)
In PTC thermistor probes, resistance increases with increased temperatures and decreases when the temperature decreases. PTC thermistors are not as widely used, but function as fuses that mitigate rises in temperature when heat should not be present. The increase of resistance that accompanies the temperature increase acts as a type of safety valve, allowing the overactive circuit to reach an upper limit.
Additionally, there are a few different types of configurations available, such as:
HSTH
Hermetically sealed thermistors feature a plastic polymer (PFA) jacket, which protects from corrosion and moisture. Applications often use them to measure the temperatures of various liquids such as industrial chemicals, oils, and liquid foods.
Bolt/Washer-Mounted Sensors
Standard-sized threaded openings or holes may use bolt- or washer-mounted sensors. These sensors have a small thermal mass that makes them suitable for applications with rapidly changing temperatures, including water tanks, equipment casings, and pipes.
Surface-Mounted Sensors
Surface-mounted sensors include adhesives on their exteriors that enable applications to stick them on curved or flat surfaces. It’s easy to apply and remove them for a wide range of applications.
Thermistor Probe Advantages & Applications
Thermistor probes offer several benefits that make them popular for use in many industries, including:
- Accuracy: Thermistor probes are consistently accurate when incremental changes occur within their specific operating range. This accuracy is the result of the significant changes in resistance per degree Celsius.
- Temperature Range: Thermistors operate in many temperature settings, with NTC thermistors functioning within a temperature range of -50 to 250 °C.
- Stability: Thermistors enable controllers to keep these devices at a consistent temperature according to the temperature feedback from the sensor.
- Sensitivity: Thermistors are highly sensitive compared to other sensors, as they’re quick to respond to temperature changes.
- Relatively Affordable: Thermistors are less expensive compared to RTDs and other sensors because of the materials they use.
A large number of commercial and industrial applications use thermistors to measure surface, liquid, or gas temperatures. Some of these potential applications include:
- Food and beverage
- Various industrial processes
- Scientific labs
- Biological applications
- Research & development facilities
Custom Thermistor Probes from Digital Instruments
At Digital Instruments, we offer a variety of custom thermistors and assemblies for nearly any application. Our experienced technicians and designers are dedicated to providing solutions that adhere to even the most stringent industry standards.
For more information about our thermistor probes and other products and solutions, request a quote from us or contact us today.