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What is the difference between 4-20mA hart communicator and ordinary 4-20mA signal?

Instrument Control
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Question added by ODINAKACHI FELIX AMAIKE , Automation specialist , NIGERIAN BREWERIES PLC,oPCO of Heineken
Date Posted: 2014/07/28
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Nayeem Sakharkar
by Nayeem Sakharkar , Assistant maintenance Supervisor , Positive packaging United

4-20mA current signal requires individual cables for individual devices where4 ma represents the least /start value and20mA respresents highest value.

HART (Highway Addressable Remote Transducer protocol) enhances the capability of4-20mA signal by allowing more than one device to function over the same set of cables. One signal is sent as analog whereas the others are sent as digital.  Example : The position of a valve or actuator can be sent as analog signal and pressure or temperature can be sent as digital signal over the same line.

 

 

Nishat Hussain
by Nishat Hussain , M/s Saudi-Oger Ltd

Odinokkachi, hello! It's true that HART-365 comminicator is a2-wire (bilingual) digital comminicator which can directly simulate4-20 ma output signal (which is also2-wire to the controller which already resides either in CCR (central control room)

Joji Francis Puthusserypady
by Joji Francis Puthusserypady , Instrument and control supervisor , ADNOC Gas Processing

Hey Odinakachi,

Good to be in touch with you. 

i suposse you are asking the option in "Hart communicator" which allows you to feed MA into the loop and a normal4-20 MA simulator. both are the same. both feeds mill amperars to the loop which can be verified in the control room.

Hart protopcol is used for communicating to the device that you are connected to which a normal mili amp simulator cannot do.

 

Let me know if you need any further clarification 

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