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Wednesday 20 May 2020
Posted in News, Thermocouple Information by Pyrosales

How do temperature sensors work?

How do temperature sensors work? They are devices to measure temperature readings through electrical signals. The sensor is made up of two metals, which generate electrical voltage or resistance once it notices a change in temperature. The temperature sensor plays a critical role in maintaining a specific temperature within any equipment used to make anything from medicine to beer. To produce these types of content, the accuracy and responsiveness of the temperature and temperature control are critical to ensuring the end product is perfect. Temperature is the most common physical measurement type in industrial applications. Accurate measurements are vital in ensuring the success of these processes. There are many applications that are not-so-obvious, which use temperature sensors. Melting chocolate, using a blast furnace, controlling a hot air balloon, freezing substances in a lab, running a motor vehicle, and firing a kiln.

Temperature sensors come in different forms, which are used for different methods of temperature management. There are two categories of temperature sensors which are contact and non-contact. Contact sensors are used mainly in hazardous areas.

The below are contact temperature sensors:

The Resistance Temperature Detector (RTD) is known as a resistance thermometer and measures the temperature by the resistance of the RTD element with the temperature. The metal can be made of different materials including platinum, nickel, or copper. However, platinum is the most accurate and therefore carries a higher cost.

The Thermocouple is a sensor made up of two wires with two different metals connected at two points. The voltage between the two wires reflects the change in temperature. Although the accuracy can be slightly lower than an RTD, they have the most extensive temperature range from -200 °C to 1750 °C and are generally more cost-effective.

The thermistor displays a precise, predictable, and large change in the alteration of various temperatures. With this large change, it means the temperatures are reflected very fast but also very accurately. With this large and fast nature, the NTC thermistor does require linearization – so there is some mathematics involved.

A thermometer is generally what we think of when we think temperature – particularly the mercury-filled glass tube. However, there are several types of thermometers available: Glass Thermometer: as above mercury/ ethanol glass tube. Ethanol is now the main liquid used in these thermometers.
Bi-Metal Thermometer: this thermometer type consists of a connected gauge and stem. The tip of the sensor has a spring that is attached to a rod, leading up to the gauge needle. The spring sits inside the stems sensing end. When heat is applied to the sensing coil, movement in the coil is created which causes the needle in the gauge to move – thus displaying the temperature.
Gas-filled & Liquid Thermometer: These thermometers are similar in terms of how they work. There is a bulb either filled with gas or liquid. This is situated inside the sensing end of the probe. When heated, the gas expands/liquid heats up which signals the attached rod to move the needle to the temperature being measured.
Digital Thermometer: A digital thermometer uses a probe such as a thermocouple or a resistance temperature detector (RTD). The temperature is measured using the probe (sensing end) and displayed as a digital reading.

The below is Non-contact temperature sensor

Infrared sensors determine temperatures from a distance, by measuring the thermal radiation emitted by an object or heat source. The applications for these are often in high temperatures or hazardous environments where you need to maintain a safe distance away from a particular body.  Thermal imaging and infrared sensors are the most common type of non-contact temperature sensors, and are used in the following circumstances: Fever detection or when the target object is moving (such as on a conveyor belt or within moving machinery), if it’s a great distance away if there’s a dangerous surrounding environment (such as high voltages) or at extremely high temperatures where a contact sensor would not function appropriately.

To simplify, a temperature sensor does just that, it senses the temperature of any content needing to be measured, whether that is solids, liquids or gases.