Detcon FP-700 - Manual (Page 28)

Model FP-700
FP-700 Instruction Manual Rev. 3.0 Page 24 of 40
NOTE: The following must be performed in order before the sensor can be placed in operation.
 AutoSpan Level = 50 %LEL. AutoSpan level must be set appropriately by the operator (Section 3.5.3).
 Gas Factor = 1.0. The Gas Factor must be set appropriately by the operator (Section 3.5.4).
 Cal Factor = 1.0. The Cal Factor must be set appropriately by the operator (Section 3.5.5).
 AutoZero: AutoZero Settings are lost and user must perform new AutoZero (Section 3.4).
 AutoSpan: AutoSpan Settings are lost and user must perform new AutoSpan (Section 3.4).
3.6 Program Features
Detcon FP-700 gas sensors 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 ITM display will continuously flash the full-scale
reading. This designates an over-range condition. The 4-20mA signal will report a 22mA output during this
time.
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/Failsafe Features
Fail-Safe/Fault Supervision
Model FP-700 sensors are designed for Fail-Safe operation. If any of the diagnostic faults listed below are
active, the ITM Display will alternately scroll the message “Fault Detected” during normal operation. At any
time while the “Fault Detected” message is scrolling, hold the programming magnet over PGM2 for 1 second
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 the AutoZero and AutoSpan Calibration faults, Bridge
Fault, Sensor Fault, Processor Fault, Memory Fault, Loop Fault, and Input Voltage Fault. The 0mA fault level