Ind Meter Adapter

Posted on Feb 4, 2014

An inductance meter could be a valuable test instrument for a hobbyist to own. However few people own them because of the high price tags found on such instruments. That`s about to change. The Inductance Meter Adapter described in this articleis a circuit that, when connected to a digital multimeter (DMM), lets you measure low-valued inductances. The project can be built for a couple dollars,

Ind Meter Adapter
Click here to download the full size of the above Circuit.

or less, depending on what parts are in your junk box. Or you can buy a kit of parts including a PC board from the source mentioned in the Parts List. The range of the Adapter is actually quite impressive. It allows your DMM to measure inductance from 3 microHenries to 7 milliHenries in two ranges. Basically, when the Adapter has an inductance connected at its input terminals, it develops a DC voltage at its output terminals that your DMM can measure and display as a calibrated inductance measurement. An analog multimeter cannot do the job because it`s input resistance is below the minimum 1-Megohm required for the adapter`s proper operation. The Adapter certainly can`t replace a fine piece of test gear, but it`s a handy little instrument for sorting unlabeled parts, and matching inductors to one another. Another great feature of the Adapter is that you can have it working in less than an hour, with or without the kit. CIRCUIT DESCRIPTION. The schematic diagram for the Adapter is shown in Fig. 1. The circuit is powered from a 9-Volt battery, B1, and an LM7805 regulator, IC2, provides a regulated 5-Volt source for the rest of ther circuit. Switch S2 turns the power on and off. The heart of the circuit is a single 74HC132 quad Scmitt NAND-gate IC1. The first gate in the package, IC1-a, is configured as an oscillator whose frequency is determined by the RC components (including trimmers R6 and R7) in its feedback loop; IC1-b...

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