Cable Resistance Guide; Catalytic Sensors - Honeywell 5704 Operating Instructions Manual

MAN0448_Issue 13_01-2010
005704-M-5001 A03249
CHAPTER 4 - INSTAllATION INSTRUCTIONS
The following sections outline how to calculate the maximum line
resistance for catalytic sensors, loop powered sensors and transmitters
powered from the System 57. See Section 11.3 for a guide on cable
selection.
11.3

Cable Resistance Guide

A guide to the resistance of various copper cable sizes is given below:
Cross Sectional Area
(mm˝) AWG
0.50
0.75
1.00
1.50
2.50
Cross Sectional Area
(mm˝) AWG
0.50
0.75
1.00
1.50
2.50
11.4

Catalytic Sensors

The maximum line resistance of cabling for a catalytic sensor varies with
the current and voltage requirements of the type of sensor installed. It is
also subject to a maximum of 10V permitted across terminals S and NS
at the Quad Relay Interface Card.
Maximum line loop resistance is calculated as follows:
R
L
Where: R =
L
V =
s
I =
s
Solid Copper Conductor
Maximum resistance at 20°C
21
19
18
16
14
Stranded Copper Conductor
Maximum resistance at 20°C
21
19
18
16
14
10 - V
s
=
I
s
Total Line Resistance (ohms). Including sensor.
Sensor Voltage (V)
Sensor Current (A)
4-17
5704 Control System
(ohm/km)
36.8
24.5
18.4
12.3
7.4
(ohm/km)
36.8
24.5
17.6
11.7
7.4