Danish Vintage LRC Meter Reveals Inside

Estimated reading time: 2 minutes

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Modern test equipment is great, but there’s something about a big meter with a swinging needle and a mirror for parallax correction that makes a device look like real gear. [Thomas] shows us a Danish LCR meter (or, as it says on the front, an RLC meter). The device passes AC through the component and uses that to determine the value based on the setting of a range switch. It looks to be in great shape and passed some quick tests. Have a look at it in the video below.

An outward inspection shows few surprises, although there is an odd set of terminals on the back labeled DC bias. This allows you to provide a DC voltage in case you have a capacitor that behaves differently when the capacitor has a DC voltage across it.

Block diagram for the MM2

The circuit can measure — as the name implies — resistance, inductance, and capacitance. The manual shows a nice block diagram if you want to understand what’s going on.

Physically opening it up was a bit of a puzzle. That older gear was often well-constructed. Inside are some nice PCBs, a lot of transistors, and beautiful wiring harnesses. Someone took their time building this unit, and it shows.

Usually, when you see gear like this, it is a bridge, and you have to zero the meter, but not so with the MM2. These days, you are likely to use a microcontroller to measure the charge and discharge rate.

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