GE HEALTHCARE E-PSMP, Technical Manual

Page: 261 / 622

Respiratory Modules, E-sCAiOVX, E-sCAiOV, E-sCAiO, E-sCOVX, E-sCOV, E-sCO
8 - 11
2062973-004
Sample flow control
The gas flow in the sampling line is monitored by measuring the gas flow at the input of the gas
pump and the reference flow to the oxygen sensor is estimated by measuring the pressure in
the reference gas flow branch. The sample flow is calculated by subtracting the reference flow
from the total gas flow. A control loop adjusts the rotation speed of the pump motor so that the
gas flow is kept close to 120ml/min.
Gas sampling self-diagnostics
The sample flow and the vacuum in the sampling system are used for continuous monitoring
of the gas sampling system. The vacuum is calculated in real time as difference of the
measured ambient and working pressures.
The self-diagnostics of the gas sampling system sends the following status data to the patient
monitor when specific triggering conditions are met: ‘Check water trap’, ‘Check sample gas
out’, ‘Replace water trap’, ‘Sample line blocked’ and ‘Continuous blockage’.
The gas pump is stopped when the 'Sample line blocked' has lasted for more than 1 minute.
The module automatically restarts the pump to check whether the abnormal situation has
been resolved so that normal gas sampling operation is possible.
The gas pump repeats 1 minute full pump, 30 seconds pump off when the ‘Continuous
blockage’ message is shown.
Figure 9 Gas tubing layout
1.3.3 MiniTPX measuring unit
The MiniTPX unit is a non dispersive infrared analyzer, measuring the absorption of the gas
sample at seven infrared wavelengths, which are selected using optical narrow band filters.
The IR source is a micro-machined heating element with an integrated collimator. From the
output of the source, the radiation is passed to a flow optimized measuring chamber.
From the sample chamber, radiation goes via a specially designed beam splitter to two
detector units, each with four thermopile detectors and integrated optical filters. The miniTPX
measuring unit has two detector units for redundancy purposes. A more detailed description of
the measuring principle can be found in section “
1.2.1. CO2, N2O, and agent measurement ”.
Each detector unit also measures the unit's temperature. The module CPU uses it for further
processing and temperature compensation of the measured raw signals.
The miniTPX unit includes an amplifier board with the following functions:
•
On-board 5V regulator and 2.5V reference source.
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