Resistance Temperature Devices (RTDs)
Like thermocouples, RTD sensors are also widely used to sense temperature specifically where linearity, accuracy and repeatability are important factors. Resistance temperature detectors are powered devices that sense changes in resistance and as a result display temperature in °F or °C. There are two commonly used industrial grade RTDs established by DIN- IEC-751 (International Electric Code) Class B + .30°C and Class A + .15°C @ 0°C. Elements in this section are 100Ω .00385 curve.
- RTD sensor elements are primarily a fine platinum coil (wire wound) or platinum deposited onto a ceramic substrate (thin film). The application will define which element to use. Most often the thin film will be used due to vibration resistance and lower cost.
- Thin film resistance temperature detector elements are commonly used when faster response time is required and minimal physical size is the issue.
- Wire wound RTD elements are widely used for industrial RTD sensors or higher temperatures (above 260°C)
- Low temperature RTDs (-50 to 260°C) are designed to be more responsive to changes in temperature.
- Mineral insulated (MgO) sheathed resistance temperature detectors are available for higher temperature applications (650°C rating)
RTD sensors are specifically useful where linearity, accuracy, interchangeability and repeatability are important.