Detcon IR-700 - Manual (Page 28)

Model IR-700
IR-700 Instruction Manual Rev. 3.1 Page 24 of 40
3.6.1 Operational Features
Over-Range
When gas greater than the full-scale range is detected, the ITM display will continuously flash the full-scale
reading of 100. This designates an over-range condition. The 4-20mA signal will report a 22mA output
during this time.
Negative Drift
In cases where the sensor may drift negative, the display will show a negative reading between 5% and 10% of
the sensors full scale range. I.E., if a 0-100ppm sensor drifts to negative 6 the display will indicate -6. In
cases where the full scale range of the sensor is less than 10ppm, due to the limited space on the display, the
decimal point will be displayed as an asterisk (*) to denote a negative reading. I.E., if a 0-5ppm sensor drifts
to negative 0.32 the display will show 0*32.
In-Calibration Status
When the sensor is engaged in AutoZero or 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 ITM is not in an
active measurement mode. This feature also allows the user to log the AutoZero and 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 cell 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.
3.6.2 Fault Diagnostic/Fail-Safe Features
Fail-Safe/Fault Supervision
Model IR-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 while the “Fault Detected” message is active, swipe the magnet over PGM1 or PGM2
to display the active fault(s). All active faults will then be reported sequentially.
Most fault conditions result in failed operation of the sensor and in those cases the 4-20mA signal is dropped
to the universal fault level of 0mA. These include Zero Fault, AutoSpan Calibration Faults, Sensor Fault,
Processor Fault, Memory Fault, Loop Fault, and Input Voltage Fault. The 0mA fault level is not employed for
a Temperature Fault and AutoSpan Reminder Fault.
For all diagnostic faults, the associated RS-485
Modbus™ fault register will be flagged to alert the user digitally.
NOTE 1: Refer to the Troubleshooting Guide section d) for guidance on fault conditions.
NOTE 2: The 0mA fault level is not employed for a Temperature Fault and AutoSpan
Reminder Fault.