Watlow CLS200 - Wiring Recommendations; Noise Suppression

CLS200 Series User’s Guide
Chapter 2: Installation
26
Wiring Recommendations
Follow these guidelines for selecting wires and cables:
• Use stranded wire. (Solid wire can be used for fixed service; it makes intermittent connections
when you move it for maintenance.)
• Use 20 AWG (0.5 mm
2
) thermocouple extension wire. Larger or smaller sizes may be difficult
to install, may break easily, or may cause intermittent connections.
• Use shielded wire. The electrical shield protects the signals and the CLS200 from electrical
noise. Connect one end of the input and output wiring shield to earth ground.
• Use copper wire for all connections other than thermocouple sensor inputs.
Table 2.1 — Cable Recommendations
FUNCTION MFR. P/N NO. OF WIRES AWG MM
2
MAXIMUM LENGTH
Analog Inputs
Belden 9154
Belden 8451
2
2
20
22
0.5
0.5
RTD Inputs
Belden 8772
Belden 9770
3
3
20
22
0.5
0.5
Thermocouple
Inputs
T/C Ext. Wire 2 20 0.5
Control Outputs
and Digital I/O
Belden 9539
Belden 9542
Ribbon Cable
9
20
50
24
24
22 to 14
0.2
0.2
0.5 to 2.5
Analog Outputs
Belden 9154
Belden 8451
2
2
20
22
0.5
0.5
Computer
Communication:
EIA/TIA-232, 422
or 485, or 20mA
Belden 9729
Belden 9730
Belden 9842
Belden 9843
Belden 9184
4
6
4
6
4
24
24
24
24
22
0.2
0.2
0.2
0.2
0.5
4,000 ft. (1,219 m)
4,000 ft. (1,219 m)
6,000 ft. (1,829 m)
Noise Suppression
The CLS200’s outputs are typically used to drive solid state relays. These relays may in turn operate
more inductive types of loads such as electromechanical relays, alarm horns and motor starters.
Such devices may generate electromagnetic interference (EMI or noise). If the controller is placed
close to sources of EMI, it may not function correctly. Below are some tips on how to recognize and
avoid problems with EMI.
For earth ground wire, use a large gauge and keep the length as short as possible. Additional
shielding may be achieved by connecting a chassis ground strap from the panel to CLS200 case.