Types of Temperature Sensors

Temperature sensors are integral to modern-day living. From thermostats to oven sensors, everyday applications are all around us, quietly regulating temperature across applications. These temperature monitoring devices are vital to maintaining and improving safety, efficiency, quality, and automation in commercial settings across various industries, including industrial and manufacturing applications.

Today, we’re examining the different types of temperature sensors and their applications in modern-day electronics, specifically four types of temperature sensors used in industry applications related to manufacturing and industrial equipment.

The easiest trivia question ever is probably: what type of sensor measures temperature? A temperature sensor, of course. These devices are electronic instruments that ​​measure the temperature of the air, liquid, and solid matter in a wide range of industries and applications. They monitor temperature by converting thermal energy into an electrical signal that can be measured and displayed at regular intervals. Temperature sensors can be wireless or hardwired into a larger computerized maintenance management system, a.k.a. a CMMS network, for streamlined access to readings.

Temperature sensors are vital to regulating temperature in applications and systems that apply to consumer and commercial use, including industrial applications to control electrical radiator heat, monitoring temperature measurements in medical applications (like MRI machines and ultrasound scanners), and environmental temperature control in laboratory settings. Different types of temperature sensors can also be found in computers to prevent overheating, food and beverage equipment for sanitary purposes, and in household appliances like freezers, refrigerators, and ovens. Temperature sensors also play a critical role in measuring surrounding air, particularly important in colder climates to prevent freezing issues.

Before we explain the different types of temperature sensors and their applications, let’s discuss the two broad categories of temperature measurement devices: contact and non-contact temperature sensors. The choice between these types is critical, as the application's setup can influence how temperature readings are obtained. 

Contact temperature sensors are efficient in applications where there are ample opportunities for contact with an object, liquid, or gas. In these cases, the contact temperature sensors measure the temperature when it is expected to be below 3400 °F (1700 °C) or above -40 °F (-40 °C). Thermistors, thermocouples, and resistance temperature detectors are contact temperature sensors.

Non-contact temperature sensors, on the other hand, do not require contact for temperature measurement, as they use infrared technology to measure the surface temperature remotely. These types of temperature sensors are ideal in applications where the object measuring is moving or making contact, which could damage the temperature probe or object or change the temperature. They are also useful when large areas need to be measured, or the object is too far away or difficult to access, like in space.

What are the different types of temperature sensors? Let's explore the temperature sensors commonly used in various industrial applications.

These temperature sensors change the resistance of the RTD element directly with temperature. They are constructed with a film and glass or ceramic core wrapped in wire, which offers more accuracy. Resistance temperature detectors are available in two-, three-, and four-wire options and are recognized for their accuracy, stability, and wide temperature range. These types of temperature sensors can be found in manufacturing processes, like metal forging and material quality control, where accurate temperature measurement is crucial.

This type of temperature sensor is highly sensitive to temperature changes within a specific range. Thermistors are typically constructed from polymer or ceramic materials covered in a glass surface, making them cheaper than RTDs yet less accurate. Thermistors are, however, more accurate compared to other types of temperature sensors (other than RTDs) due to their repeatability and quick response to variations in temperature. Thermistors are commonly used in HVAC systems for precise temperature measurement and control in heating, ventilation, and air conditioning systems.

These types of temperature sensors are indigestible to industrial and everyday applications due to their broad temperature range, durability, and relatively simple construction. The thermocouple construction involves two dissimilar metal wires (a.k.a. thermoelements), a hot junction or measurement point, a cold junction or reference point, insulation, and a protective sheath. 

Operationally, they generate a voltage based on the Seebeck Effect, where two dissimilar metals joined at one end produce a voltage proportional to the temperature difference between the hot and cold junctions. We find thermocouples in manufacturing kilns, furnaces, and other high-temperature processes or for monitoring temperatures in aerospace engines, exhaust systems, and other critical aircraft components.

Semiconductor-based sensors typically use integrated circuits, making them ideal for electrical applications. Typically, they consist of two identical diodes with temperature-sensitive voltages that detect temperature changes. Despite this linear response, they have relatively lower accuracy than other standard sensor types. Furthermore, they offer slower response times across narrow temperature ranges of approximately -70 °C to 150 °C or -94 °F to 302 °F.

Although the accuracy of different types of temperature sensors depends on the application's specific requirements, RTDs tend to be the most accurate, as they provide a nearly linear resistance-temperature relationship over a wide temperature range.

Understanding all types of temperature sensors is essential to accurate selection, as each application has different temperature sensing needs. Temperature sensors are vital to a wide range of industries, including industrial electronics, aerospace, and military and defense - and Peerless Electronics has the most diverse selection available for applications within these sectors. As an authorized stocking distributor for industry-leading leading manufacturers, you can expect only the best quality backed by over 50 value-added services, including custom-tailored technical support.