RKI Instruments 35-3010RK-04 - Manual (Page 8)

4 • 35-3010RK-04 Sample-Draw Detector
Charcoal Filter
The charcoal filter is located in the top left corner of the enclosure. It is held in place by a
metal clip. The charcoal filter is placed after the H
2
S sensor and before the CO sensor in
the flow system. It scrubs out interfering gases which may cause the CO sensor to
respond, such as H
2
S or certain hydrocarbons. Replace the charcoal filter when false high
CO readings are noticed, especially in the presence of H
2
S.
Pump
The pump is located to the left of the main circuit board near the bottom left of the sample
draw detector. 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 to the sample draw
detector.
Flowmeter
The flowmeter is attached to the main circuit board near the top left corner (see Figure 1).
A ball in the flowmeter column indicates the flow rate of the sample draw detector. The
flowmeter measures the flow in the range 0.2 to 2.0 SCFH (Standard Cubic Feet per Hour).
Although the sample draw detector will operate down to a flow of 0.6 SCFH, the
optimum flow rate is 1.2 SCFH.
Bypass Valve
The bypass valve is to the left of the flowmeter. The bypass valve adjusts the flow rate to
the sensor. Use a flat-blade screwdriver to adjust the bypass valve.
NOTE: The bypass valve allows fine adjustments of the flow rate. For a wider range of
adjustment, use the flow adjust potentiometer (see Figure 1).
Status Lights
Two status lights are above the flowmeter.
Pilot Light
The green Pilot light is on when the sample draw detector is receiving power.
Fail Light
The red Fail light is on when the sample flow rate is below the low flow level.
NOTE: The factory set low flow level is 0.6 SCFH (±0.2). See “Adjusting the Low Flow
Setting” on page 16 for instructions to adjust this setting.
Pressure Switch
The pressure switch is mounted to the opposite side of the main 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
relay to interrupt the sensor signal for the LEL channel and the 4-20 mA signal for CO
channel. This causes a downscale reading at the monitor on these channels. The low flow
level is factory-set at 0.6 SCFH (±0.2 SCFH).