Temperature Sensors & Transmitters
Temperature sensors and transmitters allow the monitoring, control, and even the measurement of temperature. At their most basic, these sensors and transmitters comprise two elements: a temperature-measuring device (the sensor part), which is the part that does the "sensing"; and a signal-processing component (the transmitter part), which converts the kind of signal generated by the "sensing" into a format that can be displayed or further processed.
Resistance temperature detectors (RTDs) and thermocouples are two of the most popular temperature-sensing technologies. As their name suggests, RTDs measure temperature by detecting changes in electrical resistance. In the case of an RTD that uses platinum, the resistance change is highly linear with temperature.
Taking a signal from a temperature sensor and converting it into a standardized output is the job of temperature transmitters. Transmitters can be used with either thermocouples or RTDs, but using them with RTDs seems to be becoming more common.
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 RTD has the slowest responsiveness over the narrowest temperature range?
An RTD with a larger mass or thicker protective sheath, such as a wire-wound RTD, typically has the slowest responsiveness and operates over a narrower temperature range compared to other RTD types like thin-film RTDs.
Does a negative temperature coefficient RTD have a semiconductor based temperature sensor?
No, a negative temperature coefficient (NTC) RTD does not have a semiconductor-based temperature sensor, as NTC sensors are typically thermistors, which differ from RTDs that use metals like platinum for temperature measurement.
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.