Fluke Calibration 4322-SYS-NAVAIR, Руководство по обслуживанию

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4322
Service Manual
2-6
External Supply Pressure Control
The Controller can set pressure from 28 kPa to 70 MPa gauge (4 psig to 10,000 psig)
using external supply gas, such as from the nitrogen cylinder or Intensifier. The sequence
below describes pressure control and measurement processes when using an external
pressure source. Refer to Figure 2-2 and Table 2-1 as required.
1.
The operator connects a nitrogen supply to the supply port and turns on the supply.
Note
When the Controller is turned on, it is completely vented and all valves are
set to the positions indicated in the “pressure vented” row of Table 2-1.
2. Pressure enters the system manifold and is blocked from entering the system by the
electrically controlled PV1 valve. When the voltage to the valve is changed, the piezo
material inside the valve contracts or expands opening and closing the valve.
3. Next, the operator sets a target pressure value. For ascending excursions, the
microprocessor configures the valves VH1, V5, and V6 in the system as shown in
Figure 2-2 and Table 2-1. The pressure transducer for the pressure range selected is
activated and starts measuring pressure. For descending excursions, the controller
decreases pressure while reading the current pressure transducer until pressure is
within the range of the pressure transducer needed for the target pressure. Then the
microprocessor configures valves VH1, V5, and V6 and starts reading the appropriate
transducer.
4. After the valves are configured, the microprocessor then applies a voltage to PV1 to
increase the pressure or applies a voltage to PV2 to decrease the pressure of the test
port and UUT (if connected).
5. Pressure is measured by one of four pressure transducer modules. Each pressure
transducer module has a specific range of pressure it measures and is isolated by
control valves V5, V6 and VH1 to prevent overpressure damage.
6. As pressure increases, the microprocessor reads the pressure readings from the
transducer pressure modules. As the pressure reaches the target pressure, the
microprocessor changes the voltage to the PV1 to slow the rate of pressure increase.
If the Controller is in dynamic control mode, the microprocessor then continues to
keep the pressure at the target pressure with small voltage adjustments to PV1 and
PV2 as required. If the Controller is in static control mode, the microprocessor
removes voltage from PV1 and PV2 once pressure is within a ready band and will re-
adjust the pressure if the pressure falls outside this band.
7. To decrease pressure to a downward target pressure, the microprocessor temporarily
opens VH2. When VH2 is opened, all pressure in the UUT and in the Controller is
sent to the CPS where waste and contaminates are trapped (see “Contamination
Prevention System” on page 2-9). When near the target pressure, the microprocessor
closes and adjusts the voltage to PV2 and PV1 to precisely control pressure to the
target pressure. This is repeated for every downward target pressure.
8. If the VENT key is pushed, or the test is complete, the microprocessor pulses VH2 in
a controlled manner until pressure approaches atmosphere. The system and all valves
are then set to the positions indicated in the “pressure vented” phase of Table 2-1.
The system stays vented until a target pressure is set again.
9. If the ABORT key is pushed, the microprocessor opens VH2 to very quickly vent the
system to atmosphere. The system and all valves are then set to the positions
indicated in the “pressure vented” phase of Table 2-1. The system stays vented until a
target pressure is set again.
Figure 2-2 shows the isolation valves, solenoids, and piezo-electric valves in the