Temperature Sensors & Transmitters
Temperature sensors and transmitters are devices used to measure and transmit temperature data in various industrial, commercial, and scientific applications.
A temperature sensor can be classified into two main types: contact and non-contact sensors. Contact sensors, such as thermocouples and resistance temperature detectors (RTDs), are in direct contact with the object being measured and provide accurate temperature readings. Non-contact sensors, such as infrared sensors, use infrared radiation to measure temperature without the need for physical contact with the object.
A temperature transmitter converts the temperature data received from the sensors into electrical signals that can be transmitted to a control system, such as a PLC or DCS. It is commonly used in industrial automation applications, such as process control and monitoring.
One common type of temperature transmitter is the 4-20 mA transmitter. This type of transmitter converts the temperature data into a 4-20 mA current signal, which can be transmitted over long distances without loss of signal quality. Other types of temperature transmitters include thermocouple transmitters, RTD transmitters, and digital temperature transmitters.
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More Information about Temperature Sensors and Transmitters
Temperature sensors and transmitters are available in various types, depending on the application requirements. Some common types of temperature sensors and transmitters include:
Resistance Temperature Detectors (RTDs)
RTDs, also known as resistance thermometers, are temperature sensors that are made of a metal wire or film, and their resistance changes with temperature. RTD sensors are highly accurate and stable over a wide temperature range, making them suitable for use in industrial environments.
Thermocouples
Thermocouples are temperature sensors that use the voltage produced by two dissimilar metals to measure temperature. Thermocouples are highly durable and can withstand high temperatures, making them suitable for use in high-temperature industrial applications.
Infrared Temperature Sensors
Infrared temperature sensors use non-contact infrared technology to measure temperature. They are ideal for use in applications where the temperature needs to be measured without making contact with the object being measured, such as in food processing or medical applications.
Digital Temperature Sensors
Digital temperature sensors are microchip-based sensors that provide accurate temperature measurements and can communicate with digital systems.
FAQs
What is the difference between an analog signal and a digital signal?
The main difference between an analog signal and a digital signal is that an analog signal is continuous, while a digital signal is discrete. Analog signals can vary in an infinite number of ways, while digital signals can only represent a finite number of values.
What is the standardized output signal for temperature probes?
The standardized output signal for temperature probes varies depending on the type of sensor being used, but in all cases, the signal is proportional to the temperature being measured.
What are thermocouple sensors?
A thermocouple is a type of temperature sensor made from two different metals that are joined at one end. When the junction of these two metals is heated or cooled, it produces a voltage, a principle known as the Seebeck effect. The voltage generated is proportional to the temperature difference between the junction and the other ends of the metal wires.
What is an RTD?
What is an RTD?
RTD stands for Resistance Temperature Detector. RTDs use a specific type of metal that, depending on the resistance measured in the metal, can determine temperature. Thin film element RTDs use a very thin layer of resistive metal adhered to a substrate, typically ceramic, and coated in glass or epoxy. Wire wound element RTDs provide greater accuracy and a wider temperature measurement range, however, over time the element wire can become stressed leading to slight measurement errors. Coiled element RTDs are the most common type of RTD and allow for strain free measurement on the wire element while still providing accurate measurement.
How do RTD elements work?
As the temperature of a metal increases, the metal's resistance to the flow of electricity increases. As the temperature of the RTD resistive element increases, the electrical resistance, measured in ohms, also increases. Each metal has a certain resistance measurement at different temperatures. Based on the resistance that is measured in a given type of metal, it can be determined what the temperature is. The most common types of metals used in RTDs are platinum, nickel and copper.
What are some advantages and disadvantages of RTDs?
RTDs provide a high level of accuracy over a wide operating range. Because of their accuracy, they are often used in situations where temperature measurement is critical. RTDs are rarely used at temperatures above 660 degrees Celsius and they do not provide the same level of accuracy or resolution as thermistors at lower temperatures.