35-3001A-14 Methane Sample-Draw Detector • 5
Status LEDs
Two status LEDs are above the flowmeter. They are also visible through the window in the housing door.
The green Pilot LED is on when the sample-draw detector is receiving power from the controller. The red
Fail LED is on when the sample flow rate is below the low flow level.
Pressure Switch
The pressure switch is mounted to the back of the flowmeter circuit board. The pressure switch monitors the
flow rate of the incoming gas sample.
If the flow rate falls below the preset low flow level, the pressure switch causes the Fail LED to turn on and
interrupts the signal from the detector. The interrupted detector signal causes a fail condition at the
controller. The low flow level is factory-set at 0.6 SCFH (±0.1 SCFH). See “Adjusting the Low Flow
Setting” on page 16 to adjust this setting.
Pump Reset Switch
The pump reset switch is located to the left of the status LEDs. When a low flow condition occurs, the pump
will be shut off. To reset the low flow condition and start the pump again, press and hold the pump reset
switch for about 2 seconds, then release.
Hydrophobic Filter
The hydrophobic filter is located toward the bottom left of the main circuit board. The filter prevents
particulates and water in the incoming gas sample from damaging the flow and detection systems. Replace
the filter when it appears dirty, discolored, or clogged.
Pump
The pump is mounted to the right side of the main circuit board. The pump pulls the gas sample into the
sample-draw detector. The pump operates on 24 VAC, which is generated from the 24 VDC supplied by the
controller.
IR CH
4
Sensor/IR CH
4
Sensor PCB
Each methane sensor is an infrared type plug-in detector. They are each installed in an IR CH
4
flow block
and the IR CH
4
flow blocks are mounted to the middle of the main circuit board. A small circuit board, the
IR CH
4
sensor PCB, with a 4-wire cable mates to the IR CH
4
sensor and retains each sensor in the flow
block. The cable is wired to an IR CH
4
amplifier. The IR CH
4
sensor PCB allows you to replace the sensor
without disconnecting the wiring.
