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After the Soviet Buran (БУРАН) program was suspended in the late 1980s, the Buran space shuttle was housed in a hangar at Baikonur. That hanger unfortunately collapsed due to structural failure in 2002, destroying the spacecraft. A clear-out of the site began a few years ago, with the parts and equipment being sold off to private collectors and resellers.

Unfortunately I couldn't afford any of the intact space suits up for auction (I can only dream), but I did manage to get hold of a temperature gauge that has actually been to space, and that's cool enough for me.

Here are some photos:

Front of gauge

Rear of gauge

Taking the metal shroud off reveals the following labelling:

Markings on gauge

An automated translation suggests that 750uA is the "Inom", which I presume means nominal current. The text at the bottom translates to "Made in USSR". The part number at the top appears to be ЭА0624, a search for which returns similar-looking DC ammeters from the Soviet era. It seems likely to me that this is a microammeter part that was repurposed as a temperature dial for the space program.

The dial moves freely and smoothly if the unit is bumped. Looking into the front glass, over the top of the plate with the markings, I can see coil windings that look like the sort of thing you'd typically see in an ammeter. Unfortunately I couldn't get a useful photo even with a microscope.

I connected a 5V source to it with a 10kΩ resistor in series, but it does nothing. Measuring across the terminals with a multimeter in resistance mode, I get an open circuit. I suspect that that it is damaged internally, since I can't think of a way in which an ammeter would appear as an open circuit.

Can anyone offer some insight into how these types of microammeter gauges are typically constructed, and what likely failures I should look for in the process of restoring this one, other than the obvious "the wire broke off the contact inside"? It wouldn't surprise me if the building collapsing on top of it knocked something loose, and that's the totality of the failure here, but I'd really like to be as careful and thorough as possible in my restoration.

Finally - and I know this is a long shot, and borderline off-topic here - does anyone have any ideas what kind of potting compound might've been used to seal this thing, and how I might remove it without damaging the plastic housing? The compound is white, hard, and cracks/crumbles when poked at with a scalpel.

I'd really like to do right by this little piece of space history and get it working again. Any help would be much appreciated.

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    \$\begingroup\$ Those look "robust" to me and I don't see any evidence of significant sharp damaging impacts. So the only way I can imagine internal damage would be if they were subjected to high-g jerk and acceleration events that were the result of indirect (not direct) impacts. As far as the potting compound goes, no clue. But I would consider calling Cotronics and asking them. They sell potting compounds and may offer some expert opinions. If you decide to remove the potting, they may supply quality product to use to replace it. They may also know something about what to use in space environments. \$\endgroup\$
    – jonk
    Mar 13, 2022 at 19:48
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    \$\begingroup\$ I'd also recommend that you write to scientists. They are often eager to help. You may start with, for example, JPL if in the US. Explain the problem and ask for someone to talk with about it, to start. Odds are that you won't get the right contact, just out of the box. But that contact very well may be able to get you closer to the right person. Repeat and rinse a few times. Likely, you will get a kindred spirit at some point and someone knowledgeable, as well. Or you can look up NASA or ESA papers on instrumentation and contact an author or two. \$\endgroup\$
    – jonk
    Mar 13, 2022 at 19:55
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    \$\begingroup\$ Then write your own answer here and let us know what you found out!! \$\endgroup\$
    – jonk
    Mar 13, 2022 at 19:55
  • \$\begingroup\$ Standard ampermeter with magnetic coil, spring and arrow. Just make with precision and durability. If it no resistance, some contacts may be gone, possible from terminal to coil. May not be reparable. Sealed with epoxy or another tough compound. Things like that nobody repair, just replacing. Did you try different current polarity? I see minus on one of teminals. \$\endgroup\$
    – user263983
    Mar 13, 2022 at 20:31
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    \$\begingroup\$ Likely was used with a thermocouple, and would have had a very low internal resistance. Perhaps someone tested it by applying a battery directly across the terminals? Or considering it was stored in a damp location until the roof fell in, electrolytic corrosion between copper wire and other metal connector did it in. Leads me to think SpaceX rides to orbit are safer... \$\endgroup\$
    – DrMoishe Pippik
    Mar 13, 2022 at 21:52

1 Answer 1

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This is a typical magnetoelectrical ammeter (first sign in a row).

Insulation strength is 1,5 kV (second sign).

It measures direct current (third sign).

It's accuracy is 2,5% (fourth sign).

It should work in vertical position (of its scale) (fifth sign).

Nominal current is a full-scale current. Negative terminal labelled with minus sign. These rules are common over the most countries (i think).

As it has designated orientation and does not have military or space signs (stamps), this is a typical industrial ammeter designed for use in electronic thermometer.

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  • \$\begingroup\$ The standard designations, agreed. But you noted the lack of military or space signs. Does this suggest that it never was used in space, as the OP believes it was? \$\endgroup\$
    – jonk
    Mar 13, 2022 at 22:02
  • \$\begingroup\$ I looked at panel photos at buran.ru/htm/soi.htm and didn't find similar meters there. \$\endgroup\$
    – Vladimir
    Mar 13, 2022 at 22:10
  • \$\begingroup\$ Makes sense to me. The OP may have been taken for a ride. Regardless, your answer is great to have! Thanks! +1 \$\endgroup\$
    – jonk
    Mar 13, 2022 at 22:21
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    \$\begingroup\$ Sorry, i haven't completed edit in 5 minutes. All electronic space equipment undergoes special test and certification and has corresponding signs. There is may be very low probability that it was part of some of dummy spaceships which were built for testing purposes, but never flied, but i can't imagine purpose of such industrial, earth ammeter in a spaceship while there was no problem to get such meter designed for space. \$\endgroup\$
    – Vladimir
    Mar 13, 2022 at 22:23
  • \$\begingroup\$ Well, if it is an ampere meter (measuring currents) then, ideally, its resistance would be zero (in order to not impede the current to measure). The OP's measurement wouldn't be surprising. The question is whether this was the display unit for the actual remote thermometer which would produce a current (does something like that exist? Would it make sense?). \$\endgroup\$
    – Peter - Reinstate Monica
    Mar 14, 2022 at 8:01

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