20Ma Loop Powered Sensors; 20Ma Transmitters - Honeywell 5704 Operating Instructions Manual

MAN0448_Issue 13_01-2010
005704-M-5001 A03249
CHAPTER 4 - INSTAllATION INSTRUCTIONS
11.5

4 - 20mA loop Powered Sensors:

The maximum line resistance of cabling for a 4 - 20mA loop powered
sensor varies with the voltage drive requirements of the type of sensor
installed. It is also subject to a 24V maximum loop drive voltage.
Maximum line loop resistance is calculated as follows:
Where: R =
L
V =
s
11.6

4 - 20mA Transmitters

The maximum line resistance of cabling for a 4 - 20mA transmitter
powered from the System 57 varies with the voltage and current
requirements of the transmitter. It is also subject to the minimum supply
voltage available from the System 57.
Maximum line loop resistance is calculated as follows:
R
L
Where: R =
L
V =
r
V =
s
I =
s
Making the above calculation using a V
worst case low dc supply situation.
The maximum resistance per core can be calculated from the above
configurations as follows:
Maximum Resistance of Core =
24 - V
s
R
L =
0.025
Total Line Resistance (ohms)
Minimum Sensor Operating Voltage (V)
V - V
r s
=
I
s
Total Line Resistance (ohms)
Minimum DC Supply to System 57 (V)
Sensor Voltage (V)
Sensor Current (A)
4-18
5704 Control System
of 18V will accommodate the
r
R
L
ohms
2