Someone requested the Galvanometer this morning for the first time in my 5 years here. It lights up albeit dimly and the spot would not move no matter what setting I used. The coil of wire was not broken and the magnet was a very strong one but there was no deflection, Any idea what the problem might be and how to fix it. It is pretty old.
Broken galvanometer
- Thread starter Muttley
- Start date
karen b
COMMITTEE
I think you need to put it on the “direct” setting for that practical.
Is the spot even just wobbling about a little, or looks fixed in place?
Daft question/not daft question. Was it on "short" when it was moved?
If you have the big demo meters, with a centre zero mA scale. try that instead of the light beam galvo - niot as sensitive, but it's how I usually do it.
Thanks for the replies. we have a centre zero mA but the deflection is tiny.
I took a look inside and fiddled with the bit which moves when you twist the "set zero" knob. No idea what I was doing but it woks perfectly now. I have put a big sticker on it to say put it on "short" when not being used and moving.
I took a look inside and fiddled with the bit which moves when you twist the "set zero" knob. No idea what I was doing but it woks perfectly now. I have put a big sticker on it to say put it on "short" when not being used and moving.
They have an extremely delacate suspension wire for the moving coil with a tiny mirror that is the moving part of the meter.
It sounds as if the coil had wedged itself when being moved and you managed to disploge it without damage. Well done.
It sounds as if the coil had wedged itself when being moved and you managed to disploge it without damage. Well done.
My colleague (who was a much better technician than me) used to overhaul these things almost every time that they went out. I never had the patience for these monstrosities - misaligned mirrors, intermittent bulb holders, dim spots, and a general refusal to be PAT tested. So I made this little amplifier box (I only had to do it once):
Nick Mitchener
COMMITTEE
reflecting galvanometers are not monstrosities, they were a huge step forward in measurement but also in telecommunications, and I think it is great they are still in use 150 years later. Also where would music concerts be without laser light shows?
When I was an apprentice c1965 we had instruments like:
`Scalamp' moving coil reflecting galvanometer
We also had an incredibly ancient galvanometer with a separate light source and scale.
My complaint is about more modern versions, as sold to schools, which are not fit for purpose.
P.S. Another good thing that has disappeared is the large Unilab demonstration meter (as used with my little amplifier).
`Scalamp' moving coil reflecting galvanometer
We also had an incredibly ancient galvanometer with a separate light source and scale.
My complaint is about more modern versions, as sold to schools, which are not fit for purpose.
P.S. Another good thing that has disappeared is the large Unilab demonstration meter (as used with my little amplifier).
Nick Mitchener
COMMITTEE
When I was an apprentice c1965 we had instruments like:
`Scalamp' moving coil reflecting galvanometer
We also had an incredibly ancient galvanometer with a separate light source and scale.
My complaint is about more modern versions, as sold to schools, which are not fit for purpose.
P.S. Another good thing that has disappeared is the large Unilab demonstration meter (as used with my little amplifier).
I have several with physical clamps, but they still rely on somebody clamping them before moving them.
I bought a couple of White's display meters with loads of dials/shunts/multipliers
karen b
COMMITTEE
Still use one like that.When I was an apprentice c1965 we had instruments like:
`Scalamp' moving coil reflecting galvanometer
We also had an incredibly ancient galvanometer with a separate light source and scale.
My complaint is about more modern versions, as sold to schools, which are not fit for purpose.
P.S. Another good thing that has disappeared is the large Unilab demonstration meter (as used with my little amplifier).
The newer galvanometer we have just drifts about the place and we can never get any kind of reading.
I've gone back to using that version after my edspot went funny.
Technician Q
(she/her)
I’m sure we have one of those somewhere.When I was an apprentice c1965 we had instruments like:
`Scalamp' moving coil reflecting galvanometer
We also had an incredibly ancient galvanometer with a separate light source and scale.
My complaint is about more modern versions, as sold to schools, which are not fit for purpose.
P.S. Another good thing that has disappeared is the large Unilab demonstration meter (as used with my little amplifier).
Nick Mitchener
COMMITTEE
I got one of the wooden ones in a job lot recently. It does work, you have to rotate the concave mirror yourself to line the dot up on the screen
the Pie unit above just works !!! well until they try to get an earth to pat test it !!When I was an apprentice c1965 we had instruments like:
`Scalamp' moving coil reflecting galvanometer
We also had an incredibly ancient galvanometer with a separate light source and scale.
My complaint is about more modern versions, as sold to schools, which are not fit for purpose.
P.S. Another good thing that has disappeared is the large Unilab demonstration meter (as used with my little amplifier).
We bought some new light spot galvos recently just lets say they won't still be in use thirty years later like the above still is
Nick Mitchener
COMMITTEE
Rewire it for a low voltage bulb and it will be fine.
A micro-voltmeter does the job nicely with a coil and magnet, we still have the galvanometers, they see little use these days mainly because the teachers don't know what they can be used for.
Technician Q
(she/her)
Can you do that? I think we have one in our “junk that’s too good to go to the skip” cupboard so if it’s just failed a PAT test and can be revived for the next one it would be very satisfying.
Nick Mitchener
COMMITTEE
The only reason it has a power input is for the bulb. You can change that to a low voltage one run from bench supply. I do that with Microscopes that fail PAT testing too. The instrument doesn't need power, just the lamp.
Technician Q
(she/her)
So I can just turn it into a very fancy 12V lamp? Perfect solution! Assuming that’s the fault!