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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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and then it sends this signal to the DCS
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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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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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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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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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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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This is area code. This is transmitter
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And this is the cable coming from the
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And this is the cable going to the DCS
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And this is one flow transmitter DP type
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differential pressure based flow
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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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all instruments in the industries
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operates on 4 to 20 millia basis
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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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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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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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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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This pressure is connected to the
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instrument. Inside there is a pressure
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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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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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I will show you the junction box also
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for the 4 to 20 millia based signals.
