GE HEALTHCARE E-PSMP, Technical Manual

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Module Frames and Modules
8 - 10
2062973-004
Working pressure transducer
The working pressure transducer measures absolute working pressure near the MiniTPX unit
and MiniOM unit. It is used for messages: ‘Sample line blocked’, ‘Check D-fend’, ‘Replace D-fend’
and ‘Check sample gas out’.
Pneumatics unit
The pneumatics unit contains the zero valve, the occlusion valve and the pneumatics block
with tubing connections.
The zero valve is activated during the zero level calibrations of gas sensors. The occlusion and
zero valves are activated when the sampling line or water trap is occluded. With the activated
valves, the gas pump generates maximal suction trough the “side flow” connector of the water
trap, thus maximizing the transfer of liquids from the wet side of the water trap to the
container.
The pneumatics block contains a network of constrictions to divide the sampled gas in correct
proportions to different parts in the module. The first branching takes place in the water trap
where incoming flow is divided to the “main flow” and “side flow”. The second branching takes
place before the MiniOM sensor.
The pneumatics block also contains a pneumatic low pass filter between gas sensors and gas
pump. The filter consists of constrictions (resistors) and volumes (capacitors) and it attenuates
the pressure pulsation generated in the gas pump so that they do not disturb the operation of
the gas sensors.
Gas pump unit
The gas pump is a membrane pump run by a brushless DC-motor. The pump is adjusted so
that the sample gas flow is kept close to its nominal value even when the flow resistances in
the sampling line of water trap change.
The pump is in a plastic enclosure to minimize the operating noise and mechanical vibration of
the pump unit. A pneumatic damping chamber is integrated to enclosure to attenuate the
pressure pulsation and noise conducted to the gas exhaust port.
Pressure measurements
The four pressure sensors on the CPU board are used to measure ambient pressure, working
pressure of the MiniTPX and MiniOM sensors and pressure of the reference gas flow to the
MiniOM sensor.