Advanced Automotive Fault Diagnosis
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LÔØI NOÙI ÑAÀU, ledklok
| 3.4 Engine analysers
3.4.1 Engine analysers Some form of engine analyser became an almost essential tool for faultfinding modern vehicle engine systems. However, hand-held equipment is now tending to replace the larger analysers. The latest machines are now generally based around a PC. This allows more facilities that can be added to by simply changing the software. Whilst engine analysers are designed to work specifically with the motor vehicle, it is worth remembering that the machine consists basically of three parts: ● multimeter; ● gas analyser; ● oscilloscope. This is not intended to imply that other available tests, such as cylinder balance, are less valid, but to show that the analyser is not magic, it is just able to present results of electrical tests in a convenient way to allow diagnosis of faults. The key compo- nent of any engine analyser is the oscilloscope facility, which allows the user to ‘see’ the signal under test. The following is a description of the facilities available on a typical engine analyser. The new concept in garage equipment design is based on a PC, specially engineered for workshop use and enabling a flexibility of use far exceeding the ability of machines previously available. Software is used to give the machine its ‘per- sonality’ as an engine analyser, system tester, wheel aligner or even any of the other uses made of PCs. Either an infrared handset or a standard ‘qwerty’ keyboard controls the machine. The information is displayed on a super VGA moni- tor giving high resolution colour graphics. Output can be sent to a standard printer when a hard copy is required for the customer. A range of external measurement modules and software application programmes is available. 32 Advanced automotive fault diagnosis Figure 3.11 Screen grab showing gauges and graphs The modules are connected to the host computer by high speed RS422 or RS232 serial communi- cation links. Application software is loaded onto a hard disk. Vehicle specific data can also be stored on disk to allow fast easy access to infor- mation but also to allow a guided test procedure. The modern trend with engine analysers seems to be to allow both guided test procedures with pass/fail recommendations for the less skilled technician, and freedom to test any electrical device using the facilities available in any rea- sonable way. This is more appropriate for the highly skilled technician. Some of the routines available on modern engine analysers are listed below. Tune-up This is a full prompted sequence that assesses each component in turn with results and diagnosis dis- played at the end of each component test. Stored data allows pass/fail diagnosis by automatically comparing results of tests with data on the disk. Printouts can be taken to show work completed. tải về 7.07 Mb. Chia sẻ với bạn bè của bạn:
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