Magnetic Affects on Vehicle Electronics
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air conditioner unitAir conditioners are another part of a vehicle that can create magnetic fields that disrupt the functioning of electronics. But first it is important to understand how an air conditioner in a vehicle works. There are six basic components: the compressor, condenser, receiver-drier, thermostatic expansion valve, the evaporator and the life-blood of the A/C system, the refrigerant. An air conditioning unit can be seen in the following figure. 
Figure 4 – Diagram of the functionality of an air conditioner [5] First there is the compressor part of the air conditioner unit. The compressor is the power unit of the A/C system, it is powered by a drive belt connected to the engine's crankshaft. When the A/C system is turned on, the compressor pumps out refrigerant vapor under high pressure and high heat to the condenser. Second there is the condenser unit. The condenser is a device used to change the high-pressure refrigerant vapor to a liquid. It is mounted ahead of the engine's radiator, and it looks very similar to a radiator with its parallel tubing and tiny cooling fins. If you look through the grille of a car and see what you think is a radiator, it is most likely the condenser. As the car moves, air flowing through the condenser removes heat from the refrigerant, changing it to a liquid state. Third refrigerant moves to the receiver-drier. This is the storage tank for the liquid refrigerant. It also removes moisture from the refrigerant. Moisture in the system can freeze and then act similarly to cholesterol in the human blood stream, causing blockage. As the compressor continues to pressurize the system, liquid refrigerant under high pressure is circulated from the receiver-drier to the thermostatic expansion valve, which is the fourth part of the air conditioner. The valve removes pressure from the liquid refrigerant so that it can expand and become refrigerant vapor in the evaporator. Fifth there is the evaporator. The evaporator is very similar to the condenser. It consists of tubes and fins and is usually mounted inside the passenger compartment. As the cold low-pressure refrigerant is released into the evaporator, it vaporizes and absorbs heat from the air in the passenger compartment. As the heat is absorbed, cool air will be available for the occupants of the vehicle. A blower fan inside the passenger compartment helps to distribute the cooler air. Sixth there is the heat-laden, low-pressure refrigerant vapor is then drawn into the compressor to start another refrigeration cycle. This is basically how an A/C unit in a vehicle works. Air conditioners create magnetic fields when they are turned on due to the electric current that is needed to power the compressor. This current going creates an electric field, and since the magnetic fields lie at 90-degree angles to the magnetic fields it creates a substantial field enough to affect the compass of a vehicle, if not accounted for. Such is the case with the Mitsubishi Endeavor. Tests were run on the Yazaki compass in this vehicle. The results will now be discussed. First tests were run to make sure that the compass calibrated in a different fashion as the Johnson Controls compass to check for patent infringements. Once it was determined that Yazaki was performing the calibration of a compass differently more tests were run to benchmark it. Then tests were run to see how fast and accurately the compass updated the display since we could not read into the registers of the compass due to lack of knowledge. Finally, tests were run to see if Yazaki correctly accounts for magnetic fields created by functions on a vehicle. So the following test was performed. First the vehicle was calibrated and turned for many circles so that it was fully calibrated and knew the magnetic fields of the earth. Then the vehicle was pointed directly west. The car was then driven in a straight line. The air conditioner unit was then turned on. When this happened the display on the compass unit moved from west to southwest, obviously as a result to the air conditioning unit. The test was now run in the north south direction. Starting with the vehicle facing north it was driven south and the air conditioning unit was turned on with the same result. Now, these tests were performed again to see the affect on the compass. Only this time the air conditioning unit would be turned on and off while traveling in a straight line. This was done to see if the compass would correct itself again. The compass would not correct itself until a couple more circles were turned. Directory: ~pribeiro -> courses -> engr302 -> Samples Samples -> Cell Phone Antennas: a look at the history and design of vhf antennas ~pribeiro -> Transmission Power Quality Benefits Realized by a smes-facts controller ~pribeiro -> The magician's nephew engr302 -> Wireless Communications: Past, Present, and Future ~pribeiro -> Michael Ward "Always winter, and never Christmas" ~pribeiro -> The Last Battle ~pribeiro -> By C. S. Lewis a sermon preached in the Church of St. Mary the Virgin, Oxford,Autumn, 1939 Download 0.51 Mb. Share with your friends:
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