RKI Instruments GX-2003 Operator's Manual download pdf (Page 14)

7 • Instrument Description GX-2003 Operator’s Manual

Sensors

The GX-2003 uses up to five sensors to monitor combustible gas,

oxygen (O2), carbon monoxide (CO), and hydrogen sulfide (H

simultaneously. The sensors are located inside the GX-2003 and are

held in their sockets by the flow chamber. The sensors use different

detection principles, as described below.

Combustible Gas Sensors

% LEL Sensor (NC-6264AT)

The % LEL sensor detects combustible gas in the % LEL range. It uses

a catalytic element for detection. The reaction of gas with oxygen on

the catalyst causes a change in the resistance of the element which

affects the current flowing through it. The current is amplified by the

GX-2003’s circuitry, converted to a measurement of combustible gas

concentration, and displayed on the LCD.

NOTE: The % LEL sensor can not be used in instruments that utilize

Bar Hole Mode or Leak Check Mode.

LEL/PPM Sensor (NC-6264ALB)

The LEL/ppm combustible sensor is a specialized version of the %

LEL sensor. It is used instead of the % LEL sensor in instruments that

are intended for use in Bar Hole Mode or Leak Check Mode. The

LEL/ppm sensor can also be used for detection in Normal Mode.

%Volume Sensor

The % volume sensor detects combustible gas in the % volume range.

It uses a thermal conductivity (TC) element for detection. The

presence of combustible gas cools the element causing a change in the

resistance of the element which affects the current flowing through it.

The current is amplified by the GX-2003’s circuitry, converted to a

measurement of combustible gas concentration, and displayed on the

LCD.

Oxygen Sensor

The O

sensor is a galvanic type of sensor. A membrane covers the cell

and allows gas to diffuse into the cell at a rate proportional to the

partial pressure of oxygen. The oxygen reacts in the cell and produces

a voltage proportional to the concentration of oxygen. The voltage is

measured by the Model GX-2003’s circuitry, converted to a

measurement of gas concentration, and displayed on the LCD.

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RKI Instruments GX-2003 Operator's Manual Page 14