Ye olde test equipment

[Eliminateur]

i know you guys are going to love this shit so i'm posting it, we just salvaged some old test equipment from my dad(that was old by the time he got it), i still haven't tested it but look at the ranges!, goes from 40mohm to ~4Mohm!
it's all built in baquelite and has some internal battery compartment that's not AA so some custom arcane pack, haven't tested it yet but i'm looking forward to it.

ah yes.... the main thing, the device in questions is a Siemens Wheatstone bridge, it's so old the markings on the back are all worn out and unreadable(they're in german, how i'd wish to be able to see what it says), the carrying pouch is pure leather!
anyone has any more info?

http://img809.imageshack.us/g/dsc00961u.jpg/

[david77]

Lovely piece you've got there.

It might not be as old as you think, production was probably sometime around 1955.

Here's what it says on the back:

http://www.radio-antik.de/images3/DSCI2600.JPG

I took the liberty to translate that for you.

CURRENT SOURCE:
Built in battery: 4,5V 3LR12
External battery 6V or 60V. The latter is needed when the accuracy in the k range shall be +/-1%.

MEASURMENT:
Connect resistor to terminals.
If resistor is unknown set range switch to 500R. Press button.
If the needle swings to the right, turn knob to the left.
If the needle swings to the left, turn knob to the right, until 0-position is reached.

CHANGING THE BATTERY:
Open bottom by loosening the screw. Bend battery contacts like shown in the picture.

MAINTENANCE OF SWITCH:
Clean contacts with pure petroleum and lubricate them with a thin layer of Vaseline.

[Eliminateur]

whoa!, i knew it was a good idea to post it here!, it's amazing you found the back of it so fast!
i thought it was older, maybe it's because i have it pretty worn out

so to have +-1% i need 60V, nice

wow!, lubricate with PETROLEUM!, i'll have to clean the switch with vaseline then... probably super old and dry by now
thanks for the data david!

[Zero999]

CURRENT SOURCE:
Built in battery: 4,5V 3LR12
External battery 6V or 60V. The latter is needed when the accuracy in the k range shall be +/-1%.

You could build a small DC-DC converter to get 60V from a 9V battery or a few AA cells.

[PetrosA]

There are small A23 12V batteries (smaller than a AAA) for a few bucks. Five of them would get your 60V

[Zero999]

There are small A23 12V batteries (smaller than a AAA) for a few bucks. Five of them would get your 60V

Yes, seen those before.

It depends on how much current it draws, on whether that's a viable option or not.

[Eliminateur]

i can easily get 60V by using both rails of my bench PSU(+-30V) as well.
those 12v batteries you mention are photo and carkey alarm ones, they stack 8 small lithium coin cells inside, but i'm not sure how much current draw does the bridge has, specially in ohm or milliohm range so no need to go the chemical batt route, if i can get upwars of 50V then it should work ok

[Psi]

you could also make 60v using a mcu or 555 timer to switch dc to ac then feed it into a diode+capacitor network to rectify and multiply the voltage up.

[Eliminateur]

that does not qualify as easily, that's a lot of hassle
(and i'm not sure it will handle the current draw)