Theory; Pneumatic Theory - PRESTON PRESSURE PS-500 User And Maintenance Manual

CHAPTER 2

THEORY

The PS-500 test box consists of two vacuum pumps linked in series, one pressure pump,
reservoirs for the pressure and vacuum, a system of metering valves, and digital displays
for indicating altitude, airspeed, and various other pressure measurements, based on
pressures sensed in the sensor transducers.
 Pneumatic Theory
Metering valves allow the operator to control the rate of flow of the air from the pressure
or vacuum sources, exiting out through the vacuum and pressure ports. The vent valves
allow for metering the produced vacuum or pressure back into the atmosphere. One
Crossbleed valve permits the operator to isolate the pressure and vacuum sides, or to
allow the balancing of pressures, or even to reverse the normal flow of pressures.
The two round gauges allow the operator to monitor the level of pressure or vacuum that
is stored in the tester's reservoirs. The switch corresponding to the pump for each
reservoir should be toggled to increase the reservoir's level of vacuum or pressure as
do not leave pumps on continuously!
needed. For maximum pump and battery life,
When the operator wishes to simulate an altitude, the Crossbleed, Vacuum, and Vacuum
Vent valves are gently closed. The vacuum pump is then energized until sufficient
vacuum is in the reservoir, as indicated on the Vacuum Reservoir Gauge. How much
vacuum will be needed depends on the desired altitude and is also affected by how long
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