SRS Labs QMS 100 Series, User Manual

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Operation 1–13
SRS QMS Gas Analyzer
Microcontroller Error Checks
The microcontroller is programmed to prevent the system from restarting after a power failure. If the
Mechanical Pump switch is turned on before line power is applied, the controller will halt and prevent
further action from taking place. It will stay halted until the Mechanical Pump switch is turned off, which
resets the system. When the system is halted after a power failure, you will see that the diaphragm
pump switch is on and the light is flashing. Under normal circumstances, the diaphragm pump switch is
never rejected, and therefore the light would be either dim or steady. Only a power failure can cause
the diaphragm pump switch to be rejected.
The microcontroller performs several error checks to assure correct operation:
•
From 2B
→
3: The capillary flow will not be started until the turbo pump is at speed. If the
pressure at the inlet to the QMS is above 5 mbar, the microcontroller opens the capillary flow in
short pulses. The valve is pulsed repeatedly until the pressure is below the setpoint.
•
At 3: If the turbo pump begins to slow down, it will be turned off and the system will retreat to
state 2A. The likely cause of a sudden slowdown of the pump is excessive pressure. The
system will wait at 2A until the pressure is okay and then try to restart the turbo pump.
•
At 3: If the pressure is above 5 mbar, the capillary flow valve is shut off and the system retreats
to state 2A. It will stay there until the pressure is satisfactory.
•
At 4 or 5: If the intermediate pressure exceeds 5 mbar, the sample valve will be closed. This
action prevents excessive pressures in the RGA chamber.
The microcontroller does not time out nor latch error conditions. This means that if the switches are set
to sample gas (State 4), the microcontroller will continuously try to reach that state.