Answer / s.k.bakshi

The 250 ohm resiatance is necessary to support the communication between transmitter and HART because it equalizes
1. loop resistance
2. barrier resistance
3.wire resistance
4. receivers resistance

Answer / anzal

WHILE USING COMMUNICATOR ITS NEED 250 OHM IN BETWEEN THE TRANSMITTER AND POWER SUPPLY......
THE COMMUNICATOR INJECT HIGH FREQUENCY IN LOOP FOR COMMUNICATING PURPOSE............
IN POWER SUPPLY USING LOW PASS FILTER...
LOW PASS FILTER ALOVE ONLY LOW FREQUENCY..HIGH FREQUENCY IT WILL BLOCK..........
THAT'S WHY IN BETWEEN 250 OHMS NEED...OTHERWISE IT WILL BLOCK THE HIGH FREQUENCY...IF HIGH FREQUENCY BLOCK IT CANNOT COMMUNICATE WITH TRANSMITTER..........

Answer / g.venkat

Because hart portocol need proper loop resistance

Answer / j shinde

For impedence matching.

Answer / carl_ellis

My friend Dan has an article on why HART needs a minimum
resistance in the loop to work.

http://blog.lesman.com/2011/10/06/add250-ohm-resistors-to-
make-hart-work/#more-68

Anzal, above, is on the right path. The loop power supply
is a low pass filter. The 1200Hz HART signal needs a
minimum resistance to develop a signal that the HART
receiver can 'see'.

Tell Dan Carl sent you.

any body please send me the old question papers of ongc test.

0 Answers   NTPC,

what is plc? Basic function of plc? application of plc in industry? What is lader diagram ? What is the main advantage to use plc in industry?

15 Answers   Schlumberger,

Why we use the double acting control valve in flow line?

3 Answers  

What the basic of communication?

4 Answers   Schneider,

if conical type tank in top LEFT side solid material coming but LT MOUNTED IN TOP OF LEFT SIDE, how to measure ultrasonic level transmitter ?

1 Answers   Cairn,

what is seebeck effect?

7 Answers  

how to calculate flow by dp transmitter?

4 Answers  

selection criteria of control valve? and selection criteria of actuator explain in brief?

0 Answers  

i m passed my engineering in 2010 in instrumentation and control engineering. my question is can i apply for software jobs or vacancies.??????????? plz give me answer soonnn......

2 Answers  

how do i calibrate mmwc pressure guage with out calibrator.if any? pls give me the ans.

1 Answers  

what is cold loop? difference between hot and cold loop?

0 Answers   Adani Power,

why 1 to 5 vdc is used for output measurment

4 Answers