In this section we will read about
- I/P Converter (Current to pressure Converter)
- Valve positioner
- Parts of a pneumatic control valve positioner
- Control Valve and its types
- Solenoid Valve
- Pneumatic Cylinder
- Butterfly Valve
- Pneumatic Globe Valve
- Work of different Parts of a Control Valve
- Pneumatic globe valve types
- Characteristics of Control Valve
- Class of a control valve
- Pressure Transmitter
- Working principle of pressure transmitter
- Pin type pressure Transmitter
- Connections of a pressure transmitter
- How signal is checked in a pressure transmitter
Working principle of pressure transmitter
In this lesson, we will study the working principle of a pressure transmitter.
The Pressure Transmitter Works on Variable Capacitance Principle. A variable capacitance pressure transducer has a capacitive plate bonded to one side of the diaphragm and another capacitive plate bonded to an unpressurized surface in close proximity to the diaphragm. A change in pressure will widen or narrow the gap between the two plates which varies the capacitance.
When Pressure is applied on Pressure Transmitter it is Applied on the Diaphragm of Pressure Transmitter, When Pressure Changes variation in Diaphragm Occurs. This variation Causes variation in Silicon Oil Filled in the Transmitter. Displacement of sensing diaphragm is proportional to differential pressure. The position of the sensing diaphragm is detected by capacitor plates on both sides of the sensing diaphragm.
This variation Causes Variation in the Capacitance Due to Capacitance Variation Current Varies means 4-20 m amp varies.
The Capacitance is Given by the Equation:
- C: Capacitance
- K: dielectric constant of the material between the plates
- S: Area of one side of one plate
- N: Number of plates
- d: distance between two adjacent plates.
A capacitance transducer operates on the principle that the physical property to be sensed changes on of the variables in the above equation (usually the distance d) which then changes the capacitance C.
Answer: The capacitive transducer or sensor is nothing but the capacitor with variable capacitance. The capacitive transducer comprises two parallel metal plates that are separated by the material such as silicon oil, which is called as the dielectric material. In the typical capacitor, the distance between the two plates is fixed, but in variable capacitance transducers, the distance between the two plates is variable.
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