Watlow MLS-PM, User Manual

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26 MLS User’s Guide
Installation
Cable Recommendations
Use these cables or their equivalent.
Noise Suppression
If the MLS outputs control dry-contact EM relays with inductive loads--
like alarm horns and motor starters--you may get Radio-Frequency
Interference (RFI, or "noise") This section explains how to avoid noise
problems; read it before you wire the MLS.
Symptoms of RFI
•
The MLS display blanks out and then reenergizes, as if power had
been turned off for a moment.
• The process value does not display correctly.
•
The MLS CPU may reset; if it does, it loses its' PID output levels.
RFI may also damage the digital output circuit--so digital outputs will
not energize. If the digital output circuit is damaged, return the
controller to Watlow-Anafaze for repair.
Avoiding RFI
Where possible, use solid state relays (SSRs) instead of electrical-
mechanical (EM) relays. If you must use EM relays, try to avoid
mounting them in the same panel as Watlow-Anafaze equipment.
Separate the 120 Vac power leads from the low level input and output
leads connected to the MLS. Don't run the digital output or PID control
output leads in bundles with 120 Vac wires. (Never run input leads in
bundles with high power leads--see the General Wiring section.)
Function MFR P/N No. of Wires AWG
Analog Inputs Belden #9154
Belden #8451 2
2 20
22
RTD Inputs Belden #8772
Belden #9770 3
3 20
22
T/C Inputs T/C Ext. Wire 2 20
Carbon Probe Input Belden #88760 2 18
Digital PID Outputs and Digital
I/O Belden #9539
Belden #9542
Ribbon Cable 9
20
50 24
24
Analog Outputs Belden #9154
Belden #8451 2
2 20
22
Computer Communication:
RS232, RS422, RS485, or 20
ma Belden #9729
Belden #9730
Belden #9842
Belden #9843 4
6
4
6 24
24
24
24