Hello everyone, myself Baradwas.
In this video I will show you some 4 to
20 milliamp based instruments. If you
see here this is a level transmitter.
This instrument measures this tank level
and generates an equivalent 4 to 20
milliamps signal
and then it sends this signal to the DCS
system.
I will show you one more instrument. It
is control wallve. Our DCS system sends
analog output which is 4 to 20 millia
signal to this control wall.
If you see here, this is the wall
positioner.
This wall positioner receives this 4 to
20 milliamp signal from the DCS system
and then accordingly regulates the
instrument air flow to the actuator.
Based on the instrument airflow the wall
will open or close. Let's say DCS given
50% signal to the wall.
What is the 50%age equivalence of the
current signal? It is 12 miampere
signal.
So when the DCS sends 12 miamp signal to
the wall positioner, it regulates the
instrument airflow such that the wall
will open 50%.
This is analog output. If we are also
using a wall feedback then we will have
one analog input to the DCS system for
measuring the actual
wall feedback.
And in this picture we can see
uh temperature transmitters. See these
two are temperature transmitters. You
can see the tag name on the top. This is
the canop. TT means temperature
transmitter.
This is area code. This is transmitter
number tag name.
And this is the cable coming from the
thermouple.
And this is the cable going to the DCS
system.
And this is one flow transmitter DP type
differential pressure based flow
transmitter.
All these instruments are 4 to 20 millia
based instruments. They support hot
protocol also for the configuration
of these instruments.
But remember
all instruments in the industries
operates on 4 to 20 millia basis
signals.
Every industry wherever you go you will
find 4 to 20 millia based instruments
and these are two wire instruments.
What is two wire
in this single cable? See this is the
single cable blue color cable. See
this is the blue color cable connected
to the transmitter.
This single cable
provides power supply to the transmitter
and then carries this 4 to 20 millia
output to the DCS system using two wire
that means one pair cable.
You can see this is flow transmitter
only one cable is connected blue color
cable. This is a two wire instrument.
That is why it is very advantageous to
the installation cost optimization when
compared to three wire or four-wire
systems.
We have three-wire instruments.
Four-wire instruments also available
but majority the popular one is two wire
instrument. And next one is present
transmitters. Here we have three
pressure transmitters. See
back side we have a pipeline. On the
pipeline we have tapping point. See this
is the pipeline and we are measuring the
pressure inside this pipeline. For that
purpose there is a tapping point and
using impulse lines. Okay. These are the
impulse tubes.
This pressure is connected to the
instrument. Inside there is a pressure
sensor
and it calculates the pressure signal
and then transmitter sends this signal
to the DCS system using 4 to 20 milliamp
basis current signals. See all these
instruments hot protocol supported for
the configuration.
All instruments will be configured
uh using hot communicator as per the
design or as per the data sheet. And
this is a flow transmitter DP type.
If you see all these signals are carried
out using one pair cable.
We will call this cable as branch cable.
These cables will go to one junction box
installed in the field
and from the junction box one more cable
will go to the control room to carry the
signals.
I will show you the junction box also
for the 4 to 20 millia based signals.