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Definition of transmitter
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- 5.2 Types of transmitters Transmitters are divided into two types 1. Pneumatic transmitters 2. Electronic transmitters 5.3
| 5.1 Definition of transmitter A transmitter is used to transmit signal from field to control room or if anywhere else is required. A transmitter takes signal from the primary measuring element and transmits that proportional signal at required place. A transmitter can transmit signal over very wide ranges. 5.2 Types of transmitters Transmitters are divided into two types 1. Pneumatic transmitters 2. Electronic transmitters 5.3 Pneumatic Transmitters To measure the signal of hazardous chemicals remotely, a pneumatic signal transmission system is used. The pneumatic transmitter output is piped to the recording or control instrument. Standard output range fora pneumatic transmitter is 3 to 15 psi, 20 to 100 Kpa, or 0.2 to 1.0 bar or Kg/cm2. Transmitter output signal is carried by tubing, usually ΒΌ inch copper or plastic, to the control room. The live zero makes it possible to distinguish between true zero and a dead instrument. Pneumatic transmitters use a force balance principle that balances an input force change to an output force change to nullify internal motion and increase accuracy. Pressure transmitters usually apply process pressures to diaphragms or bellows to generate linear force that is sensed by a pneumatic pilot that facilitates the output change to the control instrument while internally rebalancing the forces between input and output. Temperature transmitters employ sealed helium bulb elements and bellows to convert temperatures to pressures and linear forces according to the Ideal Gas Law that states that a fixed amount of gas in a fixed volume will increase its pressure proportionately to an increase in temperature. Pneumatic flow transmitters most often use a differential pressure principle which resolves a balance between two opposing pressure diaphragms which is then fed as a single force to the output section of 96 Field Instrumentation GEN Rev) the device, similarly to the simple pressure transmitter. Level sensors may use the differential pressure principle that measures liquid head, or a proportional float mechanism that measures the force change of a partially submerged float as liquid level goes up and down. Download 3.37 Mb. Share with your friends:
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