SRS Labs QMS 100 Series, Руководство пользователя

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Pressure Reducing Inlet 1-9
Technical Reference
Turbo Pump
The pump attached to the
spectrometer chamber is hybrid
turbomolecular/drag pump. The
hybrid design of this pump allows it to
exhaust at high pressure (relative to
conventional turbomolecular pumps).
The pumping speed is constant at the
nominal value of 70
l
s
-1
over a large
range of exhaust pressures. As the
exhaust pressure approaches the
maximum value, the speed begins to
drop. Figure 5 shows a
representative turbo pump speed
curve, overlaid with the speed curve
of the diaphragm pump. The two
curves overlap for a small region of
pressures, which determine the
operating range of the system.
In the case the QMS, the overlapping region is 1-5 mbar. As the turbo pump exhaust pressure
increases approaches 5 mbar, the work it performs will increase. The current monitor display on the
front panel is a good indicator of the power consumed by the pump. Running the pump near its limit
mainly causes the bearing temperature to increase. The turbo pump controller will detect if the bearings
are overheating and avoid damage by shutting down the pump. Long term operation near the
temperature limit mainly will age the bearings more quickly. The only advantage to operating the turbo
pump at higher exhaust pressures is an increase in the flow rate through the capillary. The higher
flowrate can help response time, but given the cost of a turbo pump rebuild, response time is better
addressed through capillary design.
pressure
speed
diaphragm pump
turbo pump
Figure 5. Representative speed curves for two pumps. The speed
values have been scaled to show both pumps on the same graph. The
pressure is the exhaust of turbo and the inlet of the diaphragm pump.