Watlow CLS - Manual (Page 29)

Installation
CLS User’s Guide 21
Grounding
Connect the CLS chassis to an external ground at only one point, to
avoid ground loops that can cause instrument errors or malfunctions.
Since the CLS uses a non-isolated measurement system, it has the
following connections to power supply common:
• Analog common TB1 pins 5, 6, 11, & 12
• Reference common, TB1 pin 17
• Communications ground (TB1 pins 23 & 24) if using RS-232
• Power supply ground, TB2 pin 2
• Control common (TB-18 pin 2; TB-50 pin 3 and 4)
Watlow Anafaze strongly recommends that you:
• Do not connect any one of these pins to earth ground. Do not tie
them together externally.
• Isolate outputs through solid state relays, where possible.
• Isolate RTDs or “bridge” type inputs from ground, if used.
• Isolate digital inputs from ground through solid state relays. If you
can't do that, then make sure the digital input is the only place that
one of the above pins connects to ground.
• If you are using RS-232 from an un-isolated host, don't connect any
other power common point to earth ground.