An man came to me in the early 90s with very specific plans for a
tester for auto mechanics. This fellow had been a automotive tool
and parts vendor and was an accomplished mechanic himself. At the
time, some auto manufacturers provided diagnostic data from the
on-board microcomputer, however, Ford, among others, did not. It was
extremely difficult for independent (that is, non-dealer) mechanics
to troubleshoot under-the-hood sensor problems.
My client hired me to develop a handheld tester to measure the
outputs of all the engine's sensors, including the temperature
sensors, throttle sensor, and MAP sensor. He had found a small
company that sold unique clips that could penetrate plastic wire
insulation without stripping it off, and we used them for the
temporary connections to every sensor wire the tester required.
I designed and built a battery-powered, handheld device that met
his requirements. It was driven by a microcontroller and displayed
the results on a liquid crystal display (LCD). I converted the
sensor voltage measurements to equivalent temperatures, pressures,
or percent, wherever it was appropriate. I included a removable
EPROM module with the data conversion tables because my client
wanted the ability to supply other conversion modules for other auto
manufacturers.
After I finished the prototype, I produced the manufacturing
documentation for the product, and worked with the client to develop
a custom membrane switch design.
I was fortunate to obtain input - before, during, and after this
project - from an auto mechanic. He told me it was a great idea
before I accepted the project; he told me it was a great idea when I
let him try out prototype for a day or two; and he was one of the
first mechanics to buy one. Years later, he told me he was still
using it.
