INSTRUCTION MANUAL
DPS400
56-101-01180-C
1-3
Page
1
November 5, 2003
SECTION 3:
THEORY OF OPERATION
1. PRESSURE/VACUUM REQUIREMENTS
The internal pressure pump is capable of producing a pressure of 20 psi. The vacuum pump can
supply 26 inches Hg. in systems with high volumes.
2. REGULATOR/CONTROL VALVE OPERATION
The static system pressure is controlled by an absolute pressure regulator. The pitot system
pressure is controlled by a true differential regulator that senses the pressure on the static and
pitot ports of the tester. There are also two metering valves that isolate the pitot/static systems
for leak checks and are used for rate control.
3. POWER SUPPLY CIRCUITS
The DPS400 can be powered from 115/230 VAC 47-400 Hz.. On MOD G units and later, the
power supply detects the incoming voltage 115 or 230 VAC automatically. No switches or
jumpers are needed. 28 VDC operations are NOT available on MOD G units or later.
On units before MOD G, the unit can also be powered from 28 VDC. On these units, the
power cable connector has internal jumpers, which determine the required operating voltage
(115 VAC, 230 VAC or 28 VDC).
4. PROTECTION CIRCUITS
The aircraft systems are protected against excessive rates and pressures by several failsafe
solenoid and check valves. Solenoid valve actuation is controlled by programmable limits set by
the operator on the control panel.
When the actual airspeed, altitude, or VSI approaches the protection limit programmed by the
operator, an asterisk appears next to the affected parameter on the display and warns the
operator that a limit is about to be exceeded. If no corrective action is taken and the limit is
reached, the solenoid valves actuate and isolate the aircraft systems from the tester. Asterisks
change to double asterisks to indicate protection limits have been reached, and the message
"Limit(s) Exceeded F1 to Continue" displays. Negative airspeed and negative altitude protection
limits are not programmable by the operator and are set to -30 kts and -1,800 ft. When any of
these two limits are exceeded, two asterisks immediately appear next to the exceeded parameter
and the protection circuits trip. A negative airspeed trip is indicated by an airspeed reading of 0
kts with two asterisks.