Watlow Series D8 - Manual (Page 39)

Series D8 User’s Guide Chapter 2: Installation
Doc. 0600-3120-2000 Watlow Anafaze 21
Table 2.1 Cable Recommendations
Noise Suppression
The D8 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 mo-
tor starters. Such devices may generate electromagnetic inter-
ference (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 D8 case.
Symptoms of Noise
If your controller displays the following symptoms, suspect
noise:
•
The display screen blanks out and then reenergizes as if
power had been turned off for a moment.
• The process variable value is incorrect on the controller
display.
Noise may also damage the digital output circuit such that the
digital outputs will not turn on. If the digital output circuit is
damaged, return the controller to Watlow Anafaze for repair.
Avoiding Noise
To avoid or eliminate most RFI/EMI noise problems:
Function Mfr. P/N
No. of
Wires
AWG mm
2
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
thermocouple
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