Watlow MLS - Manual (Page 43)

Installation
MLS User’s Guide 31
NOTE
Your MLS is shipped with heat outputs enabled
and cool outputs disabled. You can disable any PID
output and use it for other digital output functions.
All digital outputs and PID outputs are sink out-
puts referenced to the 5Vdc supply. These outputs
are Low when they are On.
All digital inputs are Transistor-Transistor Logic
(TTL) level inputs referenced to control common.
Outputs
This section discusses the MLS' PID control and alarm outputs.
WARNING
Control outputs are connected to the MLS's logic
ground when the control output is On (Low). Be
careful when you connect external devices that
may have a low side at voltage other than control-
ler ground, since you may create ground loops.
If you expect grounding problems, use isolated
solid state relays and isolate the control device
inputs.
The MLS provides dual PID control outputs for each loop. These
outputs are on the 50 pin ribbon cable connector which connects to the
RTB. You can enable or disable them.
• The default setting is heat outputs enabled, cool outputs disabled.
• You can program each output for on/off, TP, or DZC control.
• You can program each output for direct or reverse action.
• You can program a deadband for heat/cool; within that deadband
both outputs will be Off.
Output Wiring Recommendations
When you wire output devices to the RTB, use multicolored stranded
shielded cable for analog outputs and PID digital outputs connected to
panel mount SSRs.
• Analog outputs usually use a twisted pair.
• Digital outputs have 9 to 20 conductors, depending on wiring tech-
nique.