This was designed, keeping in mind, that sometimes we have few components available and you could not carry your DMM somewhere, but you have to make some instrument for a quick need with what is available.
Analog Dial AVO Amps-Volts-Ohms meter
IC3 LM555 is to generate -5V from 9V. That reminds me of a story, I came across a Book called CMOS Hot Ideas of Intersil. I had a chance to observe, build and learn some things here. The ICL7107 circuit was the most fascinating, I also read the books of National Semiconductor at that time.
In those days small firms used to make DPM's digital panel meters with 7107. In 1987 when i got a oppurtunity to design a DPM for a firm, I put the 555 clock in place CD4009 clock shown in intersil, to derive the -5.
Small Electronic Testing Tools - Analog Dial AVO Amps-Volts-Ohms meter
Potentiometer Dial GIF for above circuit to be used to make a hand-held avo-meter is here.
Many times we cannot carry big or expensive test instruments to the field, so we have to have a troubleshooting tool kit. Continuity testers, Logic Probes, DMM, Clamp Meters etc.. You can troubleshoot and repair Electronic Equipment easily with Meters and Continuity Tester.
It also is sometimes required to build a quick jig or fixture with electronics to troubleshoot, simulate a problem or to test the reliability or aging of components and systems. Here you need to be cost effective, fast and innovative; and build a simple system with available, affordable or procurable resources. Hence a bit of circuit design, firmware and software are essential skills for production engineering.
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