Detcon PI-700 - Manual (Page 29)

Model PI-700
PI-700 Instruction Manual Rev. 2.5 Page 25 of 54
3.6.2 Fault Diagnostic/Failsafe Features
Fail-Safe/Fault Supervision
Model PI-700 sensors are designed for Fail-Safe operation. If any of the diagnostic faults listed below are
active, the ITM Display will scroll the message “Fault Detected” every 1 minute during normal operation. At
any time during “Fault Detected” mode, holding the programming magnet over PGM1 or PGM2 for 1 second
will display the active fault(s). All active faults are reported sequentially.
Most fault conditions result in failed operation of the sensor. In these cases the 4-20mA signal is dropped to
the universal fault level of 0mA. These include the AutoSpan Calibration faults, Sensor Fault, Processor Fault,
Memory Fault, Loop Fault, and Input Voltage Fault. The 0mA fault level is not employed for Temperature or
AutoSpan Faults. For every diagnostic fault condition the associated RS-485 Modbus™ fault register will be
flagged to alert the user digitally.
NOTE: Refer to the Troubleshooting Guide section for guidance on how to address fault
conditions.
Range Fault – AutoSpan
If the sensor fails the minimum signal change criteria (Section 3.4.2) during AutoSpan sequence, the “Range
Fault” will be declared. A “Range Fault” will cause a “Fault Detected” message to flash intermittently on the
ITM display and drop the 4-20mA output to 0mA. The Modbus™ fault register bit for Range Fault will be set
and will not clear until the fault condition has been cleared. The sensor should be considered ‘Out-of-Service’
until a successful AutoSpan calibration is performed.
Stability Fault - AutoSpan
If the sensor fails the signal stability criteria (Section 3.4.2) during AutoSpan sequence, the “Stability Fault”
will be declared. A “Stability Fault” will cause a “Fault Detected” message to flash intermittently on the ITM
display and drop the mA output to 0mA. The Modbus™ fault register bit for Stability Fault will be set and
will not clear until the fault condition has been cleared. The sensor should be considered as ‘Out-of-Service’
until a successful AutoSpan calibration is performed.
Clearing Fault - AutoSpan
If the sensor fails the signal stability criteria (Section 3.4.2) during AutoSpan sequence, the “Clearing Fault”
will be declared. A “Clearing Fault” will cause a “Fault Detected” message to flash intermittently on the ITM
display and drop the mA output to 0mA. The Modbus™ fault register bit for Clearing Fault will be set and
will not clear until the fault condition has been cleared. The sensor should be considered as ‘Out-of-Service’
until a successful AutoSpan calibration is performed.
Zero Fault
If the sensor drifts to < -10% of range, an “Under-Range Fault” will be declared. An “Under-Range Fault”
will cause a “Fault Detected” message to flash intermittently on the ITM display. The Modbus™ fault register
bit for Under-Range Fault will be set and will not clear until the fault condition has been cleared. If an Under-
Range Fault occurs, the 4-20mA signal will be set at 0mA until the fault condition is resolved.
Sensor Fault
If the intelligent plug-in sensor is not plugged in, plugged in incorrectly, or there is a communication failure, a
“Sensor Fault” is declared. A “Sensor Fault” will cause a “Fault Detected” message to flash intermittently on
the ITM display. The Modbus™ fault register bit for Sensor Fault will be set and will not clear until the fault