The function of a basic resistive temperature sensor (RTD) is to measure temperature by utilizing the principle that electrical resistance changes with temperature. RTDs are commonly used in various industrial, scientific, and consumer applications to accurately and reliably measure temperature.
The basic working principle of an RTD is based on the fact that the electrical resistance of most pure metals increases linearly with temperature. Platinum is one of the most commonly used metals in RTDs due to its stable and predictable resistance-temperature relationship.
Here's how an RTD works:
Sensing Element: The RTD consists of a sensing element, which is usually made of a platinum wire or a platinum film deposited on a ceramic substrate. This sensing element acts as the temperature-sensitive component.
Electrical Resistance: At a known reference temperature, typically 0°C or 25°C (known as the nominal resistance point), the RTD has a known resistance value, often 100 ohms (PT100) or 1000 ohms (PT1000).
Temperature Sensing: When the RTD is exposed to a temperature change, its resistance changes accordingly. The resistance increases with an increase in temperature and decreases with a decrease in temperature.
Electrical Measurement: To determine the temperature, the RTD is connected to a measuring instrument such as a digital thermometer, temperature controller, or data acquisition system. A known current is passed through the RTD, and the resulting voltage drop is measured across the RTD. Using this resistance measurement and the RTD's calibration data, the temperature can be accurately calculated.
RTDs offer several advantages, including high accuracy, excellent long-term stability, and a wide temperature measurement range. They are widely used in various applications such as industrial process control, environmental monitoring, laboratory equipment, and many more. The resistance-temperature relationship of an RTD follows a nearly linear curve, which simplifies calibration and provides precise temperature readings.