35-3001A-07-03 Methane/Hydrogen Sulfide Sample-Draw Detector • 5
Sensor Flow Control Valve
The sensor flow control valve is mounted to the flowmeter circuit board above the flowmeter. The
sensor flow control valve adjusts the flow rate to the detector. Turn the valve’s knob clockwise to
increase the flow and counterclockwise to decrease the flow.
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 19 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.
Flow Baffle
A flow baffle is located at the bottom of the main circuit board, behind the hydrophobic filter. Its
function is to isolate the hydrogen sulfide sensor from vibrations in the flow line that are caused by
the pump.
IR CH
4
Sensor/IR CH
4
Sensor PCB
The methane sensor is an infrared type plug-in detector. It is installed in the IR CH
4
flow block and
the IR CH
4
flow block is mounted to the middle of the main circuit board. It is the lower of the two
flow blocks mounted to 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 it in the flow block. The cable is wired to the
IR CH
4
amplifier. The IR CH
4
sensor PCB allows you to replace the sensor without disconnecting
the wiring.
