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What are some Multimeter Tips / Tricks / Unique Measurements?

baldengineer

While looking at my humble handheld multimeter, I got to thinking about different tricks for using a DMM.

For example, the trick to check the ammeter's built-in fuse or measurements like verifying if a BJT is blown.

What are some fun measurements you can do with a DMM?

  • Measure inductance with the capacity function

  • You can make decent noise measurements, (e.g. power rail noise) but need to have a multimeter with True RMS, and decent AC bandwidth. Info on how to do it is near the bottom of this blog post: /challenges-projects/project14/diy-test-instrumentation/b/blog/posts/viewing-noise-with-a-measurement-amplifier

  • If you have a 4.5 digit or so multimeter, then it's possible to connect a thermistor to it, and measure the resistance, and then shining a laser pointer on the thermistor provides sufficient energy to warm it up, which is measurable : ) The thermistor can be placed in a small transparent glass jar, to prevent direct air currents causing too much drift.

  • Measure the on resistance of a MOSFET by using the DMM in resistance mode to charge the gate before measuring the drain-source resistance. The gate capacitance will hold its charge and keep the FET on during the channel resistance measurement.

  • in reply to shabaz

    Another impressive project that is now on my to-do list.

  • Put the DMM in the diode mode and use it to identify if a BJT is good or bad. The diode mode will give the voltage drop "Vbe" (base emitter junction) if the BJT is not damaged. I use this to check transistors bought in bulk. This also helps to identify the base emitter leads on the transitor package.

  • Some DMMs have enough voltage and current on their Ohms or diode modes to turn LEDs on - so you can tell what color they are, what their polarity is and if they work.

  • in reply to dougw

    I use this method to determine the common anode/cathode of a 7 segment display. It also helps to identify if the 7 seg is a CA or CC.

  • in reply to dougw

    I tried your suggestion on my 36-year-old fluke 77 meter using the diode testing mode and it worked. I never thought of doing that. Great share!

  • in reply to colporteur

    That is a great meter for everything else as well.