Type 1 pressure switches are installed downstream of the engine-driven pumps. They monitor the output pressure of the pump.
Type 2 pressure switches are installed downstream of the Blue electric pump and on the three HP manifolds. The first one monitors the output from the Blue electric pump. Those on the HP manifolds monitor the HP of the individual systems downstream of the leakage measurement solenoid valves.
**ON A/C ALL
The main difference between the two types of pressure switch is the pressure which they operate at; 1740 + 72.5 - 72.5 psi (120 + 5 - 5 bar) for type 1, 1450 + 72.5 - 72.5 psi (100 + 5 - 5 bar) for type 2. In addition the type 2 switches give a positive signal when the system is above its low pressure warning threshold. This signal is only used when the switches are installed on the HP manifolds.
The signals from the pressure switches are used to give low pressure indications on the ECAM display unit (through the FWC) and to make the applicable FAULT lights come on (only the switches which monitor pump output operate the FAULT lights). The signals from the pressure switches are also sent to other systems.
One pressure transmitter is installed on each HP manifold. It gives data which is sent to the SDAC. The SDAC uses the data to give the system pressure display on the ECAM.
A fourth transmitter is installed on the brake manifold (Yellow system). The data from this transmitter is sent to the wheel brake system only.
4. Power Supply
____________
The four pressure transmitters must have a 28 V DC supply. The DC busbar 103PP supplies (through circuit breaker 1841GN) the three transmitters which are installed on the HP manifolds. The transmitter which is on the brake manifold gets its 28 V DC supply from the brake system (Ref. 32-00-00).
5. Component Description
_____________________
A. Pressure Switches (1151GN, 2151GN, 3151GN, 1074GK, 2074GJ, 3074GD)
R **ON A/C 001-049, 051-099, 101-149, 151-199, 201-299, 301-399,
(Ref. Fig. 002)
R **ON A/C 401-499,
R (Ref. Fig. 002A)
R **ON A/C ALL
Both types of pressure switch are of the same basic construction. They are cylindrical with a hydraulic connection at one end and an electrical connector receptacle at the other end.
The switch assemblies are made of two main sections, the hydraulic part and the electrical part. The hydraulic part contains a hydraulically-operated piston which moves a diaphragm. The diaphragm forms the seal between the hydraulic and electrical parts of the switch.
The movement of the diaphragm is transferred to a piston which moves a pressure plate. The pressure plate touches a disk spring which is connected to the switch actuator. The switch actuator touches the switching element. The switching element itself is a sub-miniature microswitch.
The switch assembly is made so that a click of the disk spring operates the switching element. Thus, the switch always operates at the same pressure and there is no variation because of contact wear or vibration. The type 1 switch sends a low pressure signal at 1740 + 72.5 - 72.5 psi (120 + 5 - 5 bar) pressure decreasing and stops the signal before the pressure is 2200 psi (152 bar) (pressure increasing).
Pressure Switches
Figure 002
R 1EFF : 001-049, 051-099, 101-149, 151-199, 1 29-32-00Page 5 1201-299, 301-399, 1Aug 01/05 1 1 1CES 1
R Pressure Switches
R Figure 002A
R 1EFF : 401-499, 1 29-32-00 Page 6
1 1 Aug 01/05
1 1
1CES 1
The type 2 switch sends a low pressure signal at 1450 + 72.5 - 72.5 psi (100 + 5 - 5 bar) pressure decreasing, and sends a high pressure signal before the pressure is 1750 psi (120 bar) pressure increasing.
NOTE : When the type 2 switch is installed to monitor system pressure, it
____
gives a signal at both low and high pressures.
The two types of switches have different electrical connectors and also
hydraulic connections of different dimensions.
The switch assemblies are sealed units and no maintenance is necessary or
possible.
B. Hydraulic Pressure Transmitter (1065GN, 2065GN, 3065GN, 3068GN)
(Ref. Fig. 003)
The four pressure transmitters are of the same type. They are cylindrical with a hydraulic connection at one end and an electrical connector receptacle at the other end.
The transmitters are made of two main sections. The first section has the pressure-sensing element. It includes a diaphragm which is under hydraulic pressure. The diaphragm causes a piezoresistive sensing element to operate on the Wheatstone bridge principle, according to the pressure applied.
The other section of the transmitter contains two circuit boards. The circuit boards have circuits which control the input voltage and increase the strength of the output signal from the switching element. The specified input voltage is 28 V DC, but the transmitter will operate satisfactorily between 18 and 32 V DC. The output voltage varies linearly from 1 V DC for 0 bar (0 psi) to 5 V DC for 200 bar (2900 psi). The transmitters are sealed units and no maintenance is necessary or possible.
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