Following on from The Green Lamp Box

[DrStrangelove]

In a sudden rush of blood to the head I've just made three meter boxes.

One 150V dc mirror scaled meter out of a JJ instruments piece of kit.

One switchable 15V/75V/150V dc mirror scaled meter ditto.

One 250mA/500mA/1A moving iron ammeter ditto.

Acquired when clearing out The Instrument Store of yore ten or fifteen years ago.

Haven't quite finished the ammeter.

It all came from a complete three phase lab that was moved, installed, then ripped out again.

Must have cost tens of thousands back in the 1970s.

The first of the voltmeters fit the plastic box precisely.

Naturally enough, the second voltmeter was nowhere near as precise & it's fortunate that the now very oval hole is covered.

[DrStrangelove]

Turns out the moving iron ammeter is reasonably accurate on the 500mA & 1A ranges, but the 250mA range is quite odd.

It uses a current transformer and I can't remember much about those.

Checked the calibration against the 1A range on my 50 year old Avo 8.

Maybe I ought to check it all out against the magnificent ElectroDynamic Ammeter upstairs: the one in a large ventilated mahogany box with a beautiful large mirrored scale.