This is a 0.1% portable LCR bridge made by ESI and it is probably made somewhere in the 60’s. As to expect from a brand like ESI it is still spot-on. ESI is most known for their calibration gear and still exists. It is beautiful build.
I got this one from a circuits online forum user, thanks Kees ! It is in , like new, condition. The dial switch is a piece of art.
It runs on 4 D cell batteries. There was a mains power supply option that was mounted on the battery compartment lid but I do not have that.
Like most bridges it has a lot of features that make it very versatile. You can use a DC source to measure the effect of DC current on the core of inductors, the voltage coefficient of ceramic capacitors.
You can connect an external generator to measure at other frequencies. And you can connect an external detector or a scope to the bnc. There is also a pair of terminals to connect a resistance decade to extend the D/Q range.
Here a demonstration and “how to use a bridge in general” video. As an rather unusual application I show you how to analyse rechargeable batteries with a bridge.
The specs are very good for such a small bridge:
All functions, ranges and resolution: