01440D Light Industrial Gas Analyser Service Manual. 2.9
5. If not, check for correct signal and supply voltages at the connector to
the instrument display module.
6. If these are correct but the instrument display does not read correctly,
the display module may need to be replaced. Note: There is no ‘zero’
adjustment for the display module itself.
7. To set mA output, connect the DVM across pins 5(-ve) and 12(+ve)
on SK5.
8. The DVM should read 4.00mA ± 0.02mA.
9. If not, adjust RV2 on the control PCB (01420915).
2.5.2 Checking the Span
1. Connect the DVM to pins 8(-ve) and 15(+ve) on SK5.
2. Introduce span gas to the inlet at the correct pressure and flow (see
section 2.1), the DVM should read 1.0000V, ±0.0001V.
If the O2 calibration gas is air, at 20.9% purity, then the figure would
be 0.8360V ±0.0001V.
3. If not adjust span control behind flip down door on front panel. (For
oxygen units if span is not achievable then the gain of the transducer
will need adjustment. See section 2.3.2. Setting the span)
4. The display should read correct calibration value ± 1 least significant
digit.
5. If not, adjust RV5 on the front panel PCB (01420904B) so that the
display reads calibration value ±1 least significant digit.
6. To set the mA output, connect the DVM across SK5 pins 5(-ve) and
12(+ve).
7. The DVM should read 20.00 ± 0.02mA, (or 17.38 ± 0.02mA at air
point).
8. If not adjust RV3 on control PCB (01420915).
NOTE
• Set ranges to full scale (or 0-25% oxygen if air is used as the
oxygen span gas).
NOTE
• It is not essential for the output voltage to be exactly 1.0000V.
E.g. if the voltage is 0.9970V then RV5 is adjusted for a display
reading of 99.7 ±0.1.
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