RKI Instruments GD-K7D2 (24 VDC) - Manual (Page 8)

4 • Model GD-K7D2 (24 VDC) Sample Draw Transmitter
Main Circuit Board
The main circuit board includes the flow light, flow rate pot, ON/OFF switch and fuse.
The end of the board at the rear of the detection unit plugs into a socket on the installation
bracket.
Flow light
The flow light is at the top left corner of the detection unit (see Figure 2 and 3). The green
flow light is on when the GD-K7D2’s flow rate is at an acceptable flow rate. If the flow rate
drops below or rises above the acceptable flow rate, the flow light turns off.
Flow rate pot
The flow rate pot is to the right of the flow light (see Figure 2 and 3). You can adjust the
GD-K7D2’s flow rate with the flow rate pot. The pot is accessible through a hole in the
cover.
ON/OFF switch
The ON/OFF switch is to the right of the flow rate pot (see Figure 3). The On/Off switch
turns the GD-K7D2 on and off. The switch is in the ON position when the toggle switch is
in the right position.
Fuse
A 2 amp, 5 mm x 20 mm fuse is located on the middle left of the main board. It is
accessible by removing four screws that retain a metal cover over the main board.
Flowmeter
The flowmeter is below the flow light (see Figure 2 and 3). A ball in the flowmeter column
indicates the flow rate of the GD-K7D2. Two horizontal lines on the flowmeter mark the
acceptable flow rate for the GD-K7D2. Use the flow rate pot to keep the flowmeter ball
between the two lines. A flow sensor at the bottom of the flowmeter senses when the
flowmeter ball is low enough to be at the bottom of the flowmeter and initiates a low flow
alarm.
Gas Sensor
The gas sensor is below and to the right of the flowmeter (see Figure 3). Through a series
of electrical and chemical reactions, the gas sensor produces an electrical current that is
proportional to the detection range of the target gas in the test sample. Electrodes within
the gas sensor housing are surrounded by liquid electrolyte. The chemical and electrical
reactions are facilitated by the electrolyte.
A sample adapter is attached to the front of the sensor. It directs the sample over a gas
permeable membrane on the front of the sensor and into the sensor.
Amplifier
The amplifier is to the right of the sensor (see Figure 3). The amplifier converts the output
of the sensor to a 4 to 20 mA signal (that is proportional to the detection range of the GD-
K7D2) and transmits the signal to a controller. The amplifier includes the span pot, zero
pot, gain pot, and output check pins.
Span pot
The span pot is at the top of the amplifier. Use the span pot to adjust the GD-K7D2’s
response output during the calibration procedure.
Zero pot
The zero pot is below the span pot. Use the zero pot to adjust the GD-K7D2’s fresh air