4-18
Self-diagnostic messages pertaining to fail-safe operation
If the device judges, based on the result of self-diagnosis, that it cannot control the valve
properly, the device executes fail-safe operation.
The output air pressure and Travel Transmission during fail-safe operation are as follows.
<Output air pressure>
Positioner Action Pilot Relay Type Output Air Pressure
Direct action single acting zero
double acting Po1: zero
Po2: Supply Pressure
Reverse action single acting Supply Pressure
double acting double acting
Po1: Supply Pressure
Po2: zero
<Travel Transmission>
The travel transmission signal is output in accordance with the fail-safe direction (UP or
DOWN) specified by a switch. (For how to check the setting, refer to 4-2-19, “Option.”)
UP: 21.0 mA minimum
DOWN: 3.6 mA maximum
Fail-safe operation is executed if any of the following self-diagnostic messages appear.
Table 4-5 Self-diagnostic messages leading to fail-safe operation
Message
Valve Travel Detector Failure
Valve Travel Detector Out of Range
CPU Failure
RAM Failure
ROM Failure
A/D Conversion Module 1 Failure
Non-Volatile Memory Failure
Input Circuit Failure
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