WEBVTT

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Hello everyone, myself Baradwas.

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In this video I will show you some 4 to

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20 milliamp based instruments. If you

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see here this is a level transmitter.

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This instrument measures this tank level

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and generates an equivalent 4 to 20

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milliamps signal

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and then it sends this signal to the DCS

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system.

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I will show you one more instrument. It

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is control wallve. Our DCS system sends

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analog output which is 4 to 20 millia

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signal to this control wall.

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If you see here, this is the wall

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positioner.

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This wall positioner receives this 4 to

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20 milliamp signal from the DCS system

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and then accordingly regulates the

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instrument air flow to the actuator.

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Based on the instrument airflow the wall

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will open or close. Let's say DCS given

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50% signal to the wall.

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What is the 50%age equivalence of the

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current signal? It is 12 miampere

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signal.

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So when the DCS sends 12 miamp signal to

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the wall positioner, it regulates the

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instrument airflow such that the wall

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will open 50%.

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This is analog output. If we are also

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using a wall feedback then we will have

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one analog input to the DCS system for

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measuring the actual

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wall feedback.

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And in this picture we can see

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uh temperature transmitters. See these

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two are temperature transmitters. You

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can see the tag name on the top. This is

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the canop. TT means temperature

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transmitter.

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This is area code. This is transmitter

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number tag name.

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And this is the cable coming from the

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thermouple.

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And this is the cable going to the DCS

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system.

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And this is one flow transmitter DP type

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differential pressure based flow

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transmitter.

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All these instruments are 4 to 20 millia

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based instruments. They support hot

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protocol also for the configuration

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of these instruments.

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But remember

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all instruments in the industries

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operates on 4 to 20 millia basis

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signals.

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Every industry wherever you go you will

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find 4 to 20 millia based instruments

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and these are two wire instruments.

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What is two wire

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in this single cable? See this is the

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single cable blue color cable. See

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this is the blue color cable connected

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to the transmitter.

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This single cable

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provides power supply to the transmitter

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and then carries this 4 to 20 millia

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output to the DCS system using two wire

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that means one pair cable.

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You can see this is flow transmitter

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only one cable is connected blue color

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cable. This is a two wire instrument.

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That is why it is very advantageous to

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the installation cost optimization when

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compared to three wire or four-wire

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systems.

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We have three-wire instruments.

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Four-wire instruments also available

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but majority the popular one is two wire

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instrument. And next one is present

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transmitters. Here we have three

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pressure transmitters. See

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back side we have a pipeline. On the

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pipeline we have tapping point. See this

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is the pipeline and we are measuring the

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pressure inside this pipeline. For that

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purpose there is a tapping point and

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using impulse lines. Okay. These are the

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impulse tubes.

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This pressure is connected to the

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instrument. Inside there is a pressure

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sensor

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and it calculates the pressure signal

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and then transmitter sends this signal

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to the DCS system using 4 to 20 milliamp

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basis current signals. See all these

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instruments hot protocol supported for

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the configuration.

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All instruments will be configured

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uh using hot communicator as per the

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design or as per the data sheet. And

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this is a flow transmitter DP type.

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If you see all these signals are carried

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out using one pair cable.

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We will call this cable as branch cable.

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These cables will go to one junction box

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installed in the field

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and from the junction box one more cable

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will go to the control room to carry the

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signals.

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I will show you the junction box also

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for the 4 to 20 millia based signals.