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Question
Why 24VDC power Supply is used as standard for all loop
powered transmitters?
 Question Submitted By :: Instrumentation
I also faced this Question!!     Answer Posted By  
 
Answer
# 1
dear friends
as per ISA standards 24 VDC is the minimum possible voltage
at which the spark will not come,we know our transmitters
will give max output current of 27 mA here they have limit
this current bcause the power we get is less than 1 watt
(P=VxI)648mW which is not capable of producing a spark thus
they have avoided spark generation by selecting 24 VDC and
limiting currnt to 27mA.this comes under extrisic safety.
 
Is This Answer Correct ?    41 Yes 4 No
Lokendra
 
Answer
# 2
see all loop powered transmitters are capable of
withstanding 10 t0 36v dc ...as per the process requirement
it will vary.. insome industries they are using 12v dc
also.. 24 vdc is used because as per ISA there are some
standards wich will match other process reqirement like
24vdc relays for digital control also wecan use 24dc to
energize tis relays
 
Is This Answer Correct ?    9 Yes 5 No
Sivakumar
 
 
 
Answer
# 3
Because 24vdc is a minimum voltage where no possibilities of any kind of spark.
so we can prevent our costly instuments using 24 vdc.
 
Is This Answer Correct ?    3 Yes 1 No
Sagar
 
Answer
# 4
It totally depends, 24 V DC 2 wire is not always applicable
every wehere some times it is 2 wire, 3 wire (2 cable for
power up & signal & 1 cable is for earthing), some times it
will 4 wire(2 for powerup & 2 for signal).

24 V Dc is for certain limit b'coz voltage will be drop in
that case w'll use 230v AC.
 
Is This Answer Correct ?    4 Yes 4 No
Maddy2504
 
Answer
# 5
it is not possible to design capacitors,resistors with
greater ratings.since size is the restriction.
 
Is This Answer Correct ?    6 Yes 13 No
Ankur Gupta
 
Answer
# 6
as per international standard. 
Is This Answer Correct ?    9 Yes 28 No
Ln Sharma
 

 
 
 
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in which application we use bigger size actuator   5
why the derivative in PID is always set to zero?   3
 
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