Detcon TP-700 - Manual (Page 27)

Model TP-700
TP-700 Instruction Manual Rev. 3.5 Page 23 of 38
Fail-Safe/Fault Supervision
Model TP-700 MicroSafe™ 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 30 seconds 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, Heater Fault, Sensor Fault,
Processor Fault, Memory Fault, Loop Fault, and Input Voltage Fault. (The 0mA fault level is not employed
for a Temperature Fault, or during Calibration.) 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 6, for guidance on fault conditions.
Range Fault – AutoSpan
If the sensor fails the minimum signal change criteria during AutoSpan sequence (Section 3.4), the “Range
Fault” will be declared. A “Range Fault” will cause a “Fault Detected” message to scroll once a minute 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 during AutoSpan sequence (Section 3.4), the “Stability Fault” will
be declared. A “Stability Fault” will cause a “Fault Detected” message to scroll once a minute 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 during AutoSpan sequence (Section 3.4), the “Clearing Fault” will
be declared. A “Clearing Fault” will cause a “Fault Detected” message to scroll once a minute 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.
Open Heater Fault
If the sensor heater should fail and become electrically open, a “Heater Fault” will be declared. A “Heater
Fault” will cause a “Fault Detected” message to scroll once a minute on the ITM display. The Modbus™ fault
register bit for Heater Fault will be set and will not clear until the fault condition has been cleared. If a Heater
Fault occurs, the 4-20mA signal will be set at 0mA until the fault condition is resolved.
Open Sensor Fault
If the sensor film should fail and become electrically open, a “Sensor Fault” is declared. A “Sensor Fault” will
cause a “Fault Detected” message to scroll once a minute on the ITM display. The Modbus™ fault register bit
for Sensor Fault will be set and will not clear until the fault condition has been cleared. If a Sensor Fault
occurs, the 4-20mA signal will be set at 0mA until the fault condition is resolved.