Detcon 10C - Manual (Page 8)

Model 10C
1.3 Fault Circuit Functions
How the 10C Controller responds to a fault condition is determined by the configuration programmed into the
controller. Faults can be programmed as latching or non-latching, energized or de-energized, and silenceable
or non-silenceable operation. Any combination of these settings, and the set-point threshold at which a fault
will trigger, can be programmed to provide setups for almost any contingency. Some system level planning
should be exercised to determine the best configuration for the application.
10C Controllers can be set up in a Fail-Safe Fault supervisory circuit. A Fail-Safe Fault can be created by
setting the Fault Relay as Energized, and connecting the fault circuits of several 10C Controllers in electrical
series. If a fault occurs anywhere in the series circuit, the de-energized fault relay will ‘break’ the circuit,
causing a system fault. The logical “OR” of all faults in the series circuit is simply constructed with such a
method. Mainly, with this set-up, loss of power to any unit will break the circuit because of the normally-
energized coils, thus creating a “Fault Condition” due to the loss of power.
The 10C Controller is designed to detect a sensor as being “In Calibration Mode” when the 4-20mA input is
nominally 2mA. The Display will show “CAL” to signify this sensor Calibration Mode. When the 10C
Controller 4-20mA falls below 2mA, the display will change to “SENS” to signify that there is a sensor related
problem. The Fault Set-Point can be set to any point below 4mA (in steps of .05mA) so that the input of the
sensor can trigger a fault at any point below 4mA.
For 3-wire sensors, the Set-Point can be adjusted to 1.8mA so that when the sensor is in Calibration, a Fault is
not generated. If the input current falls below 1.8mA, a fault will be generated. Since most sensors reduce
their output current for internally detected faults, this set-point is a good setting.
For 2-wire sensors, the sensor uses the loop current for power and so the set-point ordinarily must be set
higher. The fault Set-Point for 2-wire sensors is suggested to be 3.5mA.
10C Control Module Instruction Manual Rev.0.B Page 4 of 25