RTD Basics Hindi

What is RTD
How RTD works
Material Used in RTD
Why Platinum is used in RTD
Types of RTD
Construction of RTD
Advantage of RTD
Working Principle
Electrical resistance of a metal changes with change in Temperature.
If temperature of measuring element increase the resistance of element also increases.
Temperature coefficient of resistance is change in electrical resistance  per degree of temperature change. This denoted by α
Wire wound Type
In wire wound Technology a coil of thin resistive wire(like Platinum) is made onto a ceramic mandrel.
It is available in 2-wire technology

Thin Film Type
In Thin Film, Very fine layer of platinum is deposited on a ceramic. After that a circuit is formed thru laser cutting. Then the platinum film and wire connections are sealed together with a glass layer.
Two Wire RTD
2 wire RTD is simplest RTD circuit. This RTD has two wire leads. In two wire RTD there is no way to compensate the Lead wires resistance of RTD. Lead resistance is also added with Measuring element. Two wire RTD is used where lead length is short and accuracy is not concern.
2. Three Wire RTD
It is most commonly used configuration used in industrial application. It RTD have three wire leads.
The Third lead wire provide the lead compensation and hence the average resistance of lead wires is reduced, which improves the accuracy of RTD. They are suitable for where wire length is long.
3. Four Wire RTD
It is most complex and accurate configuration.
These type RTD have four wire leads. The Four wire leads form a true bridge which provide best lead compensation, making it most accurate Wire configuration. Four wire RTD is used where high accuracy is require.
Advantages of RTD
High Accuracy
Long Term Stability
Good Linearity
Easy to Install
Limitations of RTD
Limited temperature range (-200 deg C to 500 deg C)
High initial price
Slower response time

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