Datex-Ohmeda S/5 B-GAS, Техническое справочное руководство

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S/5 Airway modules
Document No. 800 1005-1
45
Offset (zero) adjustment
Because the oxygen measuring unit is a differential sensor, which actually measures the difference
between the O
2
concentrations in the sample and reference gases, its output must be adjusted to
equal zero when atmospheric air is present at both inputs.
1.
Connect a digital voltmeter to the output of the O
2
measuring unit at pin 7 of connector X4
on the Gas mother board.
2. Let the monitor draw in room air and adjust the voltage to zero with the O
2
measuring unit
trim resistor designated 'ZERO' (see figure 17) in the O
2
module PC board. The
potentiometers are located at the same side of the measuring unit as the tubing connectors.
3. Perform gas calibration (see User’s Reference Manual ).
Gain adjustment
1. Adjust the O
2
measuring unit offset as described in the previous section.
2. Sample 100 % oxygen and adjust the measuring unit output to between 7.7 V and 8.3 V
with the trim resistor designated 'GAIN' (see figure 17). If the output will not exceed 7.7 V, it
is acceptable that the output exceeds at least 5 V. At that level software is still able to
compensate the output.
3. Check and if necessary readjust the offset and gain until the readings remain stable.
4. Perform gas calibration (see User’s Reference Manual ).
Temperature compensation adjustment
Factory calibrated.
Frequency adjustment
The switching frequency of the electromagnet of the O
2
measuring unit has been selected to be
110 Hz to avoid interference from harmonics of both 50 Hz and 60 Hz mains frequency.
Fine adjustment is seldom necessary. However, if you wish to reduce the effects of mechanical
resonance peaks of the cabinet which appears as high noise level of the O
2
measuring unit analog
output (above 20 mV peak to peak) it is worth of trying the fine frequency adjustment. One turn of
trimmer ’FREQUENCY ’ will change the frequency by 1.5 Hz. Try to find minimum noise but do not
deviate more than ± 5 Hz.
Gas calibration
The gas calibration is performed in the Airway Gas -menu. Please see
User’s Reference Manual
for
calibration.