Watlow Series 1500 - Manual (Page 74)

Technical Reference
74 WATLOW Series 1500 User's Manual Bad Sensor, Chapter 4
Bad Sensor Indication and Troubleshooting
Indication
When a bad (open or shorted) sensor occurs for Ch-1 or Ch-2, the ACTUAL display
will show "- - - - ". The Series 1500 control outputs in both channels de-energize
when a bad sensor occurs. The events outputs remain energized. Bad sensor on
Ch-1 will produce alarm codes A2 and A4. Bad sensor on Ch-2 will produce alarm
codes A6 and A8.
Troubleshooting
Follow this procedure to troubleshoot a suspected bad sensor:
!
1. Remove power from the unit.
2. Check each sensor input with an ohmmeter at the terminals with the sensor
installed. Use the Connection Label pasted on the right side of the Series 1500
case to locate the correct terminals. With an open sensor, the resistance will
read greater than 330 ohms. A shorted sensor will have a resistance less than
70 ohms.
3. Replace the bad sensor.
4. Apply power to the Series 1500.
!
CAUTION:
Use National
Electric Code
standard safety
procedures when
troubleshooting
an electronic
controller. Use
grounded test
equipment, non-
conductive tools
and floor safety
mats.
Bad Sensor