DOC AIRBUS | AMM A320FOIL PRESSURE INDICATING SYSTEM - DESCRIPTION AND OPERATION
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
1. Oil Pressure Transmitter
Oil Pressure Transmitter - LocationA. Description
- The oil pressure transmitter is located on the lubrication unit outlet line.
- Power supply: 28VDC from busbar 202PP.
- Pressure range: 0 to 100 psid (0 to 6.89 bar).
- Output voltage: 0.7VDC to 9VDC varying lincarly with pressure from 0 to 100 psid (0 to 6.89 bar).
- Accuracy: plus or minus 1 psid (0.07 bar), from 0 to 100 psid (0 to 6.89 bar).
B. Operation
The operating principle of the pressure transmitter is to measure a pressure by sensing the strain induced in a mechanical element, (in this case a dual cantilever beam). Deflection of the beam causes a change in resistance in the four strain gages connected as a wheatstone bridge.
These resistance changes result in a DC output voltage which is proportional to the applied pressure. The assembly is equipped with a mechanical stop: this enables the unit to withstand overpressures greater than ten times the full pressure range without changing the calibration.
Several protection features are depicted in the electronic block diagram.
They include protection from reverse voltage, transients and short circuit. Electromagnetic protection is provided by the welded stainless steel case which encloses the elements.
The operating principle of the pressure transmitter is to measure a pressure by sensing the strain induced in a mechanical element, (in this case a dual cantilever beam). Deflection of the beam causes a change in resistance in the four strain gages connected as a wheatstone bridge.
These resistance changes result in a DC output voltage which is proportional to the applied pressure. The assembly is equipped with a mechanical stop: this enables the unit to withstand overpressures greater than ten times the full pressure range without changing the calibration.
Several protection features are depicted in the electronic block diagram.
They include protection from reverse voltage, transients and short circuit. Electromagnetic protection is provided by the welded stainless steel case which encloses the elements.
2. Oil Pressure Indicating
- The analog signal from the oil pressure transmitter is sent to the SDAC1, SDAC2 and the EIU. The EIU transforms the analog signal into a digital signal.
- The digital signal is then transmitted to the ECAM through the FWCs and the DMC.
- The order of priority is as follows:
SDAC1
SDAC2
EIU. - Scale: oil pressure indication is gratuated from 0 to 100 psi (0 to 6.89 bar) on the ECAM display unit.
- Advisory level: oil pressure indication flashes green when oil pressure is higher or equal to 90 psi (6.21 bar) or is below 16 psi (1.10 bar). The indication becomes red when oil pressure is below 13 psi (0.90 bar).