Watlow CAS200 - Manual (Page 86)

Chapter 5: Troubleshooting and Reconfiguring CAS200 User’s Guide
74 Watlow Anafaze
5. To verify that the scanner hardware is working
correctly, check any input (except the pulse input) as
follows:
a) Disconnect the sensor wiring.
b) Set the INPUT TYPE to J thermocouple in the SETUP
LOOP INPUT menu.
c) Place a short across the input. The scanner should
indicate the ambient temperature on the channel
you are testing.
Earth Grounding
If you suspect a problem with the ac ground or a ground
channel:
• Measure for ac voltage between ac neutral and panel
chassis ground. If ac voltage above 2Vac is observed,
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 2Vac 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 2Vac may indicate the
ground lead is not connected to the CAS200 TB2
ground terminal.
If the above tests indicate proper ac grounding but the
scanner is indicating incorrect temperatures or process
readings:
• Verify which type of sensor is installed and that the
INPUT TYPE
parameter is set accordingly.
• For a linear voltage or current input, check that the
correct input scaling resistors are installed (page 82)
and check the input scaling parameter settings (page
54).
• If readings are erratic, look for sources of electrical
noise. SeeNoise Suppression on page 29.
• Eliminate possible ground channels. SeeConnecting
the TB50 to the CAS200 on page 22.
• Contact your supplier for further troubleshooting
guidance. SeeReturning Your Unit on page 68.