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This discussion reminds me of a project that I did sometime ago. There's no microcontroller or anything real fancy in this, but it can give an accurate (go / no go) indication, both audible and visual - for many resistive components. The user simply selects an acceptable maximum level of resistance (below or equal to this level is the pass level for a good component) - then this gizmo just returns the results as valid or invalid via a LED & buzzer.

However, it's very limited. At the time I just wanted something done real quick and dead cheap. The unit can be built for less than the cost of a bus ticket, but it's range is limited to a few hundred ohms only. Another restriction is that, there's no provision for setting a minimum level of acceptable resistance. It has its place, bet auto electricians love it!

The published article can be seen here: <a href="http://siliconchip.com.au/cms/A_30755/article.html" target="_blank">Programmable Continuity Probe</a>
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