
RTDs

Resistance temperature detectors (RTDs) measure temperature based on the principle that as the temperature of a metal increases, so does the resistance to the flow of electricity. When an electrical current is applied to the RTD, the metallic element is used to measure the resistance of the passing electrical current. As the temperature increases, the resistance increases. The resistance value can be converted to temperature based on the known resistance characteristics of the metallic element. RTDs are adaptable to most industrial applications because of their wide temperature range (-330 degrees Fahrenheit to 1560 degrees Fahrenheit) and their exceptional accuracy to within 0.1 degree.
ACI Hazardous Transmitter Series temperature transmitters are mounted in an industrial connection head style enclosure. The transmitters are protected from moisture and corrosion in harsh environments due to the epoxy coating. The sensors are manufactured using a double encapsulation process, which eliminates the effects of moisture on the sensors and increases response times. For better accuracy, use with A/TTM Series transmitters which include a secondary calibration process that removes most of the sensor error over the calibrated temperature span.
ACI High Temperature Duct Series sensors and transmitters are a single point duct sensor designed with a three wire RTD sensor assembly and a 316 Series stainless steel probe. The three wire sensors can be used with a two wire transmitter by connecting the two colored wires to one of the RTD terminal blocks with the third wire going to the second RTD terminal block.
Products
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.