Gunson Gastester G4125 Handbook

Handbook

Digital Exhaust CO Analyser with Pulse Pump

GASTESTER

GASTESTER

Part No. G4125

Index

1. Kit Contents .......................................... 4

2. Assembly .............................................. 4

3. Descriptions and controls ................... 5

4. Preparations before use ...................... 6

5. Instructions for use .............................. 7

6. Further information .............................. 8

7. Common problems ............................... 9

8. Warranty ................................................ 11

32

Gastester is an exhaust gas analyser that works on the “hot wire” or “thermal conductivity”
principle: the thermal conductivity of exhaust gas varies in proportion to the amount of carbon
monoxide present. Exhaust gas is pumped through the Gastester by an externally mounted
pulse pump.

The pulse pump uses the positive and negative pressure waves generated by the exhaust gas to
force exhaust gas through the Gastester.

The pump consists of a diaphragm with one way valve and thus the pump will only be heard to
click when connected to the exhaust.

CO Function Specification:

Calibrated range: 0-10% CO

(indicates un-calibrated to 20% C)

Accuracy: +/- 0.5% CO typical

(throughout the indicated range 0.5% CO to 6.5% CO)

Note: The Gastester measures the CO level only of the exhaust gas and is therefore not
suitable for MOT or diagnostic checks where an accuracy greater than +- 0.5% CO is
required.

DISPLAY:

This is calibrated in volume percent carbon monoxide (CO%).

CALIBRATION CONTROL:

This is used to set the reading of the display to show 2.0% at the start of the tests, before the
probe is inserted into the exhaust pipe.

Note: The calibrate position represents what the instrument should register when the
probe is in fresh air. It is coincidental that air should measure the same as exhaust gas
with 2% CO. When the probe is subsequently inserted into the exhaust pipe, the display of
the instrument may increase or fall from the calibrate condition.

TWO CORE CABLE WITH CLIPS:

(for connecting to the car battery)

EXHAUST PROBE:

The aluminium pipe is for insertion into the exhaust pipe and is held in position by the metal
springs which press against the inside of the exhaust pipe.

NB: In use the pipe from the exhaust probe should slope down continuously to the pulse pump/
water trap so that water runs down and may be automatically expelled from the drain pipe.

1. Kit Contents

1. Gastester instrument including collector box and pulse pump/water trap assembly

2. Metal exhaust probe with retaining springs

3. Flexible plastic pipes (3 lengths)

4. Instruction handbook

2. Assembly

• In cold conditions, warming the various plastic pipes will assist assembly.

• Press the shortest pipe onto the lower port of the pulse pump/water trap as shown in the
diagrams Figures 1 and 2. This is the automatic water drain.

• The longest plastic pipe is connected to the pulse pump inlet (centre port) and the other end
to the aluminium exhaust probe tube.

• Connect the remaining plastic pipe between the pulse pump (top) outlet and the collector box
inlet. (This connection is intentionally vented at the inlet boss). The connection to the collector
box inlet needs to be pressed fully home.

Figure 2

4

Figure 1

1. Kit Contents

2. Assembly

5

3. Descriptions
and Controls