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Hello everyone, myself Baras. In this
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video I will discuss briefly about 4 to
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20 millia based signals.
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Let's say we have a flow transmitter.
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And it is hotbased smart flow
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It is configured with 0 to 100 m cube
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It supports output 4 to 20 millia basin
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We have a DCS system distributed control
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Now this DCS system is connected with
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this instrument using two wires.
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This is the positive wire and this is
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the negative. DCS uh provides 24 volts
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DC power supply to the failed
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This flow transmitter measures the flow
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Let's say for example the flow is 0 m
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cube per hour. There is no flow at all.
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So the transmitter regulates the loop
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accordingly as per the measured flow
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What is the signal range? 4 to 20 millia
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signal. The four represents lower range
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value. The 20 represents upper range
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Right now the flow is zero.
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Then this flow transmitter regulates the
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loop current to the 4 milliampere.
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See the flow transmitter sending 4
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The DCS measures this loop current and
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then displays to the operator.
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Okay. So on the operator computer it is
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displaying 0 m cube per hour. So this is
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the basic concept for a 4 to 20 millia
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based instrument which is configured in
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Let's say the flow increased to 25 m
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Again the transmitter measures this flow
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and updates the loop current
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Now the transmitter sending 8 miampere
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The DCS receives this 8 milliampere
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and the DCS is already configured with
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the flow transmitter details.
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For example, the transmitter's range is
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0 to 100 m cube per hour and its
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equivalent signal is 4 to 20 miampere
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signal. Accordingly, the DCS
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uh converts this measured milliampere
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into the equivalent flow rate and then
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displays onto the computer graphics.
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The computer graphics is 25 m cube per
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Similarly, let's say the flow is
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increased to 50 m cube per hour. Again
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transmitter sends 12 milliampere signal
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to the DCS system. The DCS converts this
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12 milliampere into equivalent flow rate
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and displays 50 m cube per hour
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in the computer graphics.
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Similarly the flow is increased to let's
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say 75 m cube per hour and transmitter
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sends 16 miampere signal to the DCS
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system. Again DCS system updates this
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value in the computer graphics. This
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computer graphics nothing but operator
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workstations or engineering
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Let's say the flow reached maximum
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100 m cube per hour. Then transmitter
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updates this loop current again. The
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maximum signal is 100 m cube per hour
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flow signal. And what is the current
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What is the maximum current signal? You
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can see the 20 is the maximum signal in
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this range. So the transmitter sends 20
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milliampere signal to the DCS system and
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DCS updates the flow rate on the
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So this is the traditional 4 to 20
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millia based instruments configuration
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In the next video, I will discuss
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briefly about heart protocol.
5:02
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5:05
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