Interested to Buy Any Domain ? << Click Here >> for more details...
how to connect 3 wire 4-20 mA transmitter in Plc system PLC
system and how explain how the measuring data communicate
with plc system.
- 1 Answers
- 17095 Views
- I also Faced
- E-Mail Answers
Answer Posted / sam
We normally use a clean separate power source to power all
the instrumentation on the plant including the DCS and
PLC's. This instrumentation power source is going through a
UPS and a inverter backup system to smooth and minimize
power failures. Each zone in the plant normally have its own
24VDC power supply unit, but they are all backed up by the
same UPS.
The UPS can normally keep the instrumentation and other
emergency and critical power for about 6 hours in case of a
total main power failure.
In your 3 wire system the supply to your TX will be from
this external power source, and the loop power for your 4 to
20 ma will be generated by the same TX and will not come
from the PLC or DCS as with a loop power 2-wire systems.
Since the external power to your TX is the same as the 24VDC
power it generates for the signal, you can use the negative
as a common. This common(OV) and the 4 to 20mA(24VDC) signal
is then connected to the PLC as for a normal 2-wire loop
powered TX.
This common from your TX is 0V and is the same as the 0V of
the PLC or DCS since they are all from the same UPS.
The PLC or DCS will only get the positive of your TX as the
input signal, since all the negatives of the inputs are all
connected together on a common 0V bar close to the the PLC
or DCS and only one wire from this negatives bar is then
daisy chained to each input. The negative from your TX you
therefore also need to connect to this common negative bar
of the PLC or DCS and only the positive goes to the input
connection.
The only thing you need to remember is that the 3 and 4 wire
systems are externally powered systems and are therefore
active inputs or source inputs and that the loop powered 2
wire system is a passive or sink type input. This you then
need to set up inside the PLC or DCS input configuration
parameters.
Good luck
| Is This Answer Correct ? | 13 Yes | 3 No |
Post New Answer View All Answers
Dear Sir/Madam,im going to attend Hpcl written exams on feb 17th in instrumentation stream..can anyone send me the HPCL model papers and pattern of HPCL ....i ve not yet attended anything in HPCL...so i dont know how it comes...so just i need some model test papers and pattern ..pls help me friends...
With N nodes and B branches what will have a network ???
Why flow/pressure transmitter before control valve?
Tell me the field calibration procedure step by step with diagram of pressure gauge, pressure switch, pressure transmitter, temperature switch, level switch, flow switch, flow transmitter.
What is wet leg condition and why is it used?
What are the application of bernoulli’s theorem?
you are on site,the plant trips,you are approached by operations,what do you do?
List three types Level Switches with their working principles
how to calculate range of level transmitter?
IS there any effect of vortex in low pressure side of the transmiter after the orific in feed water line? if yes then what is the calculation?
What are the interlocks we have to check during the start up of LP/HP compressor?
when a magnet is heated?
If we increase only P what will be controller action ?
what is the difference between active & reactive power?
What are the type of bonnets in the control valves?
