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
Types of RTD
In this Lesson, we will Discuss the Types of RTD.
RTD can be Categorized according to two types.
- According to Connections.
- In Simplex Signal goes to one location only.
- In Duplex Signal Goes to two Different Locations. for example: to PLC/DCS and to indicator
In Simplex only one Side is available with three wires.
2. According to Wires.
- 2 wire RTD.
- RTD has 2 wires is known as 2 wire RTD.
- 3 wire RTD.
- RTD has 3 wires is known as 3 wire RTD.
- 4 wire RTD.
- RTD has 4 wires is known as 4 wire RTD.
- 2 wire RTD is used for short distances.
- 3 wire RTD is used for long distances. A third wire is used for Resistance compensation. Resistance compensation means when a signal is coming from large distance wire resistance is not added.
- The various wiring arrangements are designed to reduce and/or eliminate any errors introduced due to resistance changes of the lead wires when they also undergo temperature changes. RTDs used for electrical equipment generally use either a three-wire system or a four-wire system having paired lead wires.
The four-wire system is little affected by temperature-induced resistance changes in lead-wires, and, of all the arrangements, it is affected least by stray currents. It, therefore, is used to measure temperature differences and is used generally for making very accurate measurements.
The three-wire system is generally satisfactory for industrial measurement using a secondary instrument that is remote, say, more than 3 meters distant from the RTD.
Although the error caused by temperature change in the leads is virtually eliminated in a 3-wire arrangement, a slight non-linearity in the resistance change is introduced with this scheme.
Commonly used RTD Materials:
• Platinum (most popular and accurate)
• Balco (rare)
• Tungsten (rare)
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