Checking Cross Sensitivity - Bosch ETT 008.31 Repair Instructions

b) Fine-tuning the mean value
Set function switch S 60 to position 1 (mean values). Select the HC channel using the "Select" button, and simultaneously press
"Enter o" to switch on the fine-tuning function.
°C display window:
HC display window:
Engine-speed window: The calibration factor accepted during the last fine-tuning is displayed.
With the "Enter o " or "Test u " buttons, change the calibration factor in such a way that the displayed value exactly matches the
test-gas value.
! Do not press any buttons!
Introduce a flow of upper-range gas into the analyzer and check that the display deviates from the test-gas value by less than 2%.
In this case, fine-tuning of this measuring range is now complete.
If, however, the display error is greater than 2%, the upper-range value must now be re-calibrated as described in a) above.
In all cases, now press the "Select" button. The calibration factor of the mean value is now accepted and the next possible function
displayed.
Continue fine-tuning with the CO measuring channel, small measuring range.
6.4

Checking cross sensitivity

Here, the device's cross sensitivity to condensation is checked.
Remove the test-gas hose from the test-gas inlet of the device.
Prepare the gas-wash (bead) bottle, filled with an effective water column of approx. 3 cm, as illustrated below; do not connect up yet.
! Take care not to connect the hose to the wrong side of the gas-wash bottle, as otherwise the device will suck up water.
- Press the pump button on the exhaust-gas analyzer (start analysis).
- Wait until zero adjustment of the exhaust-gas analyzer is complete.
- Watch which values appear for the gas-measuring channels once the displays have settled.
- Connect the gas-wash bottle to the test-gas inlet via a hose.
- Check the influence of condensation:
Maximum disturbing influence on
If cross sensitivity is outside tolerance, clean the analyzer part (see Section 10.4).
d.Ei d.Ei
d.Ei (set mena value) d.Ei d.Ei
Current measured value
HC measuring channel
CO measuring channel
CO
459512/3Ha
measuring channel
2
< 10 ppm
< 0.005 % vol.
< 0.1 % vol.
27