Watlow CAS - Manual (Page 79)

Troubleshooting
CAS User’s Guide 69
Troubleshooting Stand-Alone Systems
The CAS is only part of a control system- be sure to check other parts of
the system, like thermocouples, before you assume that the unit is
broken. To check inputs and outputs, follow these procedures.
Checking an Analog Input
To check any input except the pulse input, follow these steps:
1. Disconnect the sensor wiring.
2. Set the input sensor to type J T/C from the Setup menus.
3. Place a short across the input.
The process variable should indicate ambient temperature. If it does not,
call Watlow Anafaze for an RMA number and return the unit to Watlow
Anafaze for repair.
To check thermocouple inputs, remove the thermocouple leads and use
an ohm meter to measure between the In+ and In- terminals of TB1.
Thermocouple inputs should not read above 200 ohms.
Checking Digital I/O
The following steps will help you test digital inputs and outputs.
TB-50 Test
1. Plug in the power supply, if you have not already done so.
2. Measure the +5Vdc supply at the TB-50:
A. Connect the voltmeter's Common lead to TB-50 screw terminal
#3.
B. Connect the voltmeter's Power lead to TB-50 screw terminal
#1. The voltage should be 4.75 to 5.25 Vdc.