Page 340 - Understanding Automotive Electronics

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AUTOMOTIVE INSTRUMENTATION 9

display device could use a raster-type display strategy similar to that explained
above for a vacuum-tube CRT.
THE GLASS COCKPIT
The development of a cost-effective solid-state equivalent of the CRT can
have enormous application in automotive instrumentation. It can yield a
completely reconfigurable display system similar to the multifunction display
used in some modern transport aircraft. Such displays are termed a glass cockpit
in aircraft parlance. It is also known as an electronic flight information system
(EFIS).
A single CRT acting as a display for a digital instrumentation system has
the capability of displaying any of several choices of data readout, including
1. Navigation data
2. Subsystem status parameters
3. Attitude (artificial horizon)
4. Air data (airspeed, altitude, etc.)
It can also be used for diagnosis of problems with various aircraft subsystems. In
this case it can present a pictorial diagram of any aircraft subsystem (hydraulic
system or electrical system) so that the flight crew doesn’t have to resort to
hunting through a manual for the aircraft to diagnose a problem with a
subsystem.
One of the benefits of an automotive glass cockpit is its great flexibility.
Any message in any format can be displayed. In fact, the format can be chosen
by the driver via a set of switches or by a keypad arrangement. The driver selects
a particular display format from a number of choices and the display will be
reconfigured to his choice by software, that is, by the program stored in the
instrumentation computer. A likely default choice would include a standard
display having speed and fuel quantity and the capability of displaying warning
messages to the driver.
Another benefit of the EFIS-type display is the capability of displaying
diagnostic information to a service technician. The service tech can select a
display mode that presents fault codes from any vehicle subsystem whenever
the car is taken for repairs or during routine maintenance operations.
Of particular importance is the capability of digital instrumentation to
identify intermittent faults. The instrumentation computer can store fault
codes with a time stamp that gives the time of occurrence to indicate to a
service technician that a particular component or subsystem is experiencing
intermittent failures. Such failures are extremely difficult to diagnose because
they are often not present when the car is brought in for service. In this mode of
operation the instrumentation computer along with its software-reconfigurable
display is serving a role somewhat analogous to a flight data recorder on an
aircraft.

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