Watlow PPC-2000 - Manual (Page 174)

Chapter 4: Troubleshooting PPC-2000 User’s Guide
148 Watlow Anafaze Doc.# 30002-00 Rev 2.3
PPC-2021 - 2025 Analog Input
Refer to the following descriptions of LED indicators when
troubleshooting the analog input modules.
• Error 3 Red LED blinking in sync with Green Status
LED: Indicates an open thermocouple.
Corrective Actions:
Verify that the correct sensor keys are installed correctly.
See Sensor Keys on page 46.
Check for an open thermocouple alarm and repair the cor-
responding thermocouple.
If the input is not used, make sure it is not selected as the
PV Source for any channel. Failed sensors are only re-
ported for an input chosen as the PV Source for a channel.
• Error 3 Red LED on or blinking but not in sync with
Green Status LED: Indicates common mode overvoltage.
The cause could be either a transitional noise source or a
steady state signal, such as an AC continuous source
electrically tied into an input line.
Corrective Actions:
Locate the source of the noise and remove it.
Remove ground loop problems.
Check cabling - loose cables or input wires may cause in-
termittent noise.
• Error 4 Red LED on: Indicates a reference voltage
overload. The precision 10Vdc source is being overdrawn.
The LED will glow and increase with intensity as more
current is overdrawn.
Corrective Actions:
If an AITB is used with an analog input module, check to
make sure all key cards are inserted properly. Reverse in-
sertion will cause the LED to light.
If the 10V reference on the AITBs are used to power an ex-
ternal circuit (i.e., bridges, etc.) make sure the total
current required does not exceed the specified limit. Refer
to Chapter 7, Specifications for current information. These
conditions will not harm the voltage source.