OLCT 700/710 TP
Page 24 of 45
Rev. C.1
OLCT 700/710 TP Instruction Manual
3.6
Program Features
Oldham OLCT 700/710 TP H
2
S gas detectors incorporate a comprehensive set of diagnostic features to
achieve Fail-Safe Operation. These Operational features and Failsafe Diagnostic features are detailed
below.
3.6.1
Operational Features
Over-Range
When gas greater than the full-scale range is detected, the OLCT 700/710 display will continuously flash
the full-scale reading (20, 50, 100ppm, 200ppm). This designates an over-range condition. The 4-20mA
signal will report a 22mA output during this time.
In-Calibration Status
When the detector is engaged in AutoSpan calibration, the 4-20mA output signal is taken to 2.0mA and the
in-calibration Modbus™ Status Register bit 14 is set. This alerts the user that the OLCT 700/710 is not in
an active measurement mode. This feature also allows the user to log the AutoSpan events via their master
control system.
Sensor Life
Sensor Life is calculated after each AutoSpan calibration and is reported as an indicator of remaining
service life. It is reported in the “View Sensor Status” menu and as a RS-485 Modbus™ register bit.
Sensor Life is reported on a scale of 0-100%. When Sensor Life falls below 25%, the sensor should be
replaced within a reasonable maintenance schedule.
Last AutoSpan Date
This reports the number of days that have elapsed since the last successful AutoSpan. This is reported in
the View Sensor Status menu. After 180 days, an AutoSpan Fault will be declared.
3.6.2
Fault Diagnostic/Failsafe Features
Fail-Safe/Fault Supervision
OLCT 700/710 TP MicroSafe™ detectors 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 detector. 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 0, 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 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 OLCT 700/710 should be considered
“Out-of-Service” until a successful AutoSpan calibration is performed.
Summary of Contents for 700 TP Series
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