Answers were Sorted based on User's Feedback
Answer / ranganadh
Long distance communication mA signal is preferable than
mV, V signals to avoid noise. It cann't be predictable with
0 mA, whether the loop was broken or the signal itself. So
to avoid loop break problems we consider 4mA as the lowest
signal. Moreover, it is recommended to put a 250 ohms
resistor at the input terminals of the instrument to get
1VDC for 4mA and 5 VDC for the 20mA and further these
signals will be amplified by instrumentation amplifier in
the instrument circuit.
|Is This Answer Correct ?||8 Yes||2 No|
Answer / jazz
4-20 mA signal differentiates live process 0% with 4mA
signal with a wire break (0 mA), current is also used for
transmission because even if your receiver or PLC/DCS card
is far away current signal sent proportionately by the
transmitter will be received as the same current at the
receiver/PLC/DCS card, although it is converted as a voltage
signal (1 to 5 VDC) by a 250ohm resistor, since
micro-processor process signals in voltage levels.
|Is This Answer Correct ?||1 Yes||0 No|
What is difference between reset and initialization in system.
How it the difference between force balance system and dispalacement balance system?
Explain PID controller tuning & any one method used for it.
What is the diffrence between ff tx and non ff tx
what is meant by nuclear power plant?
Explain level troll principle & interface level measurement.
How many are the types of instrument cables in terms of No. of pair.
how to control motor load with rpm or vfd
what is the formula for changing Range of Transmitter from X mmwc to some Y mmwc with respect to DCS NCMH flow range from x NCMH to y NCMH?
Which is the best field foundation bus. ( FF ) Yokogawa, Honeywell or others ?
what is the use of glycol filling in seal pot (or) condensate pot in instrument impluse line?
You are looking at the RS-485-side of an RS-232/RS-485 converter and the power supply voltage for the converter is +5V. Under idle conditions (no transmission), and assuming you have enabled the RS-485 output: what would you expect at: (a) Output A measured against output B (b) Output A measured against ground (c) Output B measured against ground