Watlow CLS200 - Manual (Page 188)

Chapter 9: Troubleshooting and Reconfiguring CLS200 Series User’s Guide
172 Watlow Anafaze Doc.# 0600-3050-2000
Earth Grounding
If you suspect a problem with the ac ground or a ground loop:
• Measure for ac voltage between ac neutral and panel
chassis ground. If ac voltage above 2V
Å (ac) is ob-
served, then there may be a problem with the ac power
wiring. This should be corrected per local electrical
codes.
• With ac power on, measure for ac voltage that may be
present between control panels’ chassis grounds. Any
ac voltage above 2V
Å (ac) may indicate problems with
the ac ground circuit.
• Check for ac voltage on thermocouples with the heater
power on. A control output providing power to the
heaters will increase the ac voltage if there is heater
leakage and an improper grounding circuit. Measure
from either positive or negative thermocouple lead to
ac ground. AC voltage above 2V
Å (ac) may indicate the
ground lead is not connected to the CLS200 TB2
ground terminal.
If the above tests indicate proper ac grounding but the con-
troller is indicating incorrect temperatures or process read-
ings:
• Verify which type of sensor is installed and that the
INPUT TYPE parameter is set accordingly.
• For an RTD or linear voltage or current input, check
that the correct input scaling resistors are installed
(page 180) and check the input scaling parameter set-
tings (page 86).
• If readings are erratic, look for sources of electrical
noise. See Noise Suppression on page 22.
• Eliminate possible ground loops. See Ground Loops on
page 24.
• Contact your supplier for further troubleshooting
guidance. See Returning Your Unit on page 164.
Checking Control Outputs
To check control outputs:
• Set the loop you want to check to manual mode.
• Set the output power percentage to the desired level.
• Set the output type to ON/OFF or TP (see Chapter 4,
Setup).
If the control output is not connected to an output device
like an SSR, connect an LED in series with a 1 k
Ω
resistor
from +5V to the output. (Tie the anode of the LED to +5V.)
The LED should be off when the output is 0% and on when
the output is 100%.