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# RTD Working Principle

RTD stands for Resistance Temperature Detector, which is a type of temperature sensor widely used in various industries and applications. The working principle of an RTD is based on the relationship between electrical resistance and temperature.

RTDs are typically constructed using a length of pure or alloyed metal wire, such as platinum (Pt), nickel (Ni), or copper (Cu). Platinum RTDs are the most commonly used due to their excellent stability and accuracy over a wide temperature range.

## How to calculate the Temperature from Resistance Value?

PT100 Resistance to Temperature Converter

## Working Principle of RTD

Change in Resistance with Temperature: RTDs exploit the characteristic of metals where their electrical resistance changes with temperature. As the temperature of the RTD changes, the resistance of the metal wire also changes in a predictable manner.

Resistance vs Temperature Plot

## Resistance vs Temperature Plot

Linear Relationship: RTDs, particularly platinum RTDs, exhibit a nearly linear relationship between resistance and temperature over a specific temperature range. This linear relationship allows for accurate and reliable temperature measurements.

Resistance Measurement: To measure the resistance of the RTD accurately, it is connected to a Wheatstone bridge circuit. The bridge circuit consists of four resistors, with the RTD forming one of the arms. The bridge circuit balances the resistance of the RTD against the other resistors, producing a voltage output proportional to the temperature.

Temperature Calculation: The output voltage from the Wheatstone bridge circuit is then converted into temperature using calibration curves or mathematical equations specific to the RTD type. These calibration curves are determined during the manufacturing process and are based on the known resistance-temperature relationship of the RTD material.

Accuracy and Calibration: RTDs offer high accuracy and stability, providing precise temperature measurements. To ensure accuracy, RTDs are often calibrated against known temperature references, such as a reference thermometer, to verify their performance and make necessary adjustments if required.

Applications: RTDs find extensive use in various industries, including manufacturing, process control, HVAC, automotive, aerospace, and scientific research. They are particularly suitable for applications requiring high accuracy, repeatability, and stability over a wide temperature range.

In summary, RTDs work by exploiting the change in electrical resistance of metal wire with temperature. By measuring the resistance and converting it into temperature using calibration curves, RTDs provide accurate and reliable temperature measurements in a variety of applications.