The basic function of a Resistive Temperature Sensor (RTD) is to measure temperature by exploiting the predictable change in electrical resistance with temperature. RTDs are passive devices made of a metal or a metal alloy with a well-defined resistance-temperature relationship. The most common metal used in RTDs is platinum, and this type is referred to as a Platinum RTD (Pt100 or Pt1000), where the numbers indicate the nominal resistance at 0 degrees Celsius (e.g., Pt100 has a resistance of 100 ohms at 0°C).
The operating principle of an RTD is based on the fact that as temperature increases, the resistance of the metal also increases in a nearly linear manner. This resistance change is used to infer the temperature being measured. Here's how it works:
RTD Element: The RTD typically consists of a thin wire or coil made of the metal alloy, usually platinum, wound into a small, stable, and precise package.
Electrical Connection: The RTD is connected to a circuit, which passes a small electric current through the RTD element.
Resistance Measurement: As temperature changes, the resistance of the RTD changes accordingly. The circuit measures the resistance and converts it into a corresponding temperature value using the known resistance-temperature relationship of the RTD material.
Calibration: To ensure accurate temperature measurement, RTDs are usually calibrated, and the relationship between resistance and temperature is characterized. Calibration data is used to create a temperature-resistance table or mathematical equation that allows for accurate temperature readings.
RTDs are widely used in various industries and applications due to their accuracy, stability, and reliability. They are commonly found in temperature measurement and control systems, industrial processes, scientific research, HVAC (heating, ventilation, and air conditioning) systems, and more.