1/28/18 by Dave

Inductor DCR Measurement

How do you check the resistance of an inductor? You can't just use your multimeter on ohms setting.

Suppose you need to measure a device like an inductor with DC resistance in the milliohm range. We had a production quality issue and needed to evaluate some inductors. The target resistance of the part was between 63 and 70 milliohms. Try to measure it with your Fluke 87V and you'll read something in the 0.5 ohm range. So how do you accurately measure it without an expensive micro-ohm measuring instrument? This is how we did it: DCR Measure Make a "test fixture" from copper tape and a half business card. Add Kelvin sense leads. Solder the inductor on the fixture. Connect the Fluke 87V to the sense leads in voltage measurement mode and connect the power supply to the (copper tape) power leads with current limit set at 1 amp. The reading in millivolts drop on the sense leads is equal to milliohms of DC resistance in the part. Done.

By: Dave

Dave is an expert in circuit design, PCB layout, and EMC - skills that have served him well consulting for companies big and small for the last decade. In addition to 10+ years as an electronics consultant, Dave spent his career in the automotive industry from engineering to upper management. Dave is a registered Professional Engineer (Mechanical). He also holds a MS in Computer Science (Laurence Tech 06') and a BS in Mechanical Engineering (GMI 86').

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