In this section we will read about
- Current to pressure Converter (I/P Converter)
- Control Valve positioner or Pneumatic positioner
- Parts of a pneumatic control valve positioner
- Control Valve and its types
- Solenoid Valve
- Pneumatic Cylinder
- Butterfly Valve
- Globe Valve or pneumatic globe valve
- Parts of a Control Valve
- Pneumatic globe valve types
- Control Valve Characteristics
- Class of a control valve
- Pressure Transmitter
- pressure transmitter working principle
- Pin type pressure Transmitter
- Pressure Transmitter connections
- pressure transmitter signal checking
- Flow transmitter
How to check RTD
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- In this lesson, we will study How to check RTD.
- Resistance temperature Detector as the name indicates Detects Temperature and gives the output as resistance.
- The short form of Resistance Temperature Detector is RTD.
- RTD is a Temperature Sensor.
- Resistance Temperature Detectors (RTDs) give a linear change in resistance with respect to temperature.
- RTDs are a positive temperature coefficient. i.e. Resistance increases with an increase in temperature.
- Platinum is Commonly used in RTDs because its temperature Resistance characteristic is more linear in comparison to copper and nickel.
- RTD types are broadly classified according to the different sensing elements used.
- Platinum, Nickel, and Copper are the most commonly used sensing elements.
- Platinum is considered the best as it has the widest temperature range. This is shown in the resistance versus temperature graph below.
- Platinum type RTD is also known for its best interchangeability than copper and nickel. It also has the highest time stability.
How to check an RTD
- There are three wires in RTD. Out of the two wires are short-circuited as shown in the figure. The same color wires are short-circuited.
- In the above figure, blue colour wires are short-circuited.
- The different colour wire will show the same resistance with other same colour wires.
- Now the resistance will be calculated by using the following formula
Where Rt is resistance at T degrees Celcius.
R0 is the resistance at 0 degrees Celcius.
T is the temperature that we need to calculate.
@ is alpha that is temperature coefficient. Value of Alpha is .0385 for Platinum.
Now for PT 100 temperature will be Calculated by using formula
[( Resistance Shown by Multimeter- 100)/0.385]
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