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 Forum index » DIY Hardware and Software
needle meters
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elmegil



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PostPosted: Mon Nov 19, 2012 7:11 pm    Post subject: needle meters Reply with quote  Mark this post and the followings unread

I just came into possession of a couple pieces of equipment (one of them an old meter, the other...who knows what it actually is for, I haven't taken it apart yet) with nice needle meters in them.

Curious what folks think they might be useful for in a synth (not really interested in VU meters).
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bubzy



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PostPosted: Tue Nov 20, 2012 3:14 am    Post subject: Reply with quote  Mark this post and the followings unread

lfo meter?
the problem is, that any application that you may have would look the same as a vu meter Very Happy
perhaps a multimeter panel?
current indicator,
you could attach it to a dual pot and watch the needle move when you move the pot.

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Dave Kendall



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PostPosted: Wed Nov 21, 2012 7:56 pm    Post subject: Reply with quote  Mark this post and the followings unread

A couple of different switchable functions might be useful if it's going in its own module.
1/ A regular AC/DC voltage meter
2/ A Phase difference meter, like in broadcast gear for checking compliance (mono compatibility) Could be fun/useful in a modular too.

+1 on Buzby's suggestion for a current meter.

No idea how easy any of this would be to actually source driver circuits for and build though.....

cheers,
Dave

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elmegil



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PostPosted: Wed Nov 21, 2012 9:11 pm    Post subject: Reply with quote  Mark this post and the followings unread

One of them is coming out of a beat up old meter, so that might not be terribly hard. The phase difference, now that's pretty intriguing, but I'm sure that's likely to be harder to source.

Thanks for the ideas guys Smile
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Uncle Krunkus
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PostPosted: Thu Nov 22, 2012 4:37 am    Post subject: Reply with quote  Mark this post and the followings unread

I'd be using it to monitor modulation sources of somekind. Maybe even just install one, but make it's monitoing source switchable with a one pole, however many throw you want, rotary switch. Then the interface only needs to be built once. And it would be little more than an attenuverter (2*op-amps) set with trimmers for calibration, and a drive circuit, which would probably be a single (possibly darlington type) transistor.

Possible switchable inputs could be - (based on my system)
LFO 1
LFO 2
ENV 1
ENV 2
S&H
LFRND
CHAOS 1
CHAOS 2
etc.

And I think it would be a really cool part of any synth by the way! Cool

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elmegil



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PostPosted: Thu Nov 22, 2012 10:03 pm    Post subject: Reply with quote  Mark this post and the followings unread

One of these is in a big box (roughly 24" x 10" x 8") that turns out to be a PH controller. My father worked for Monsanto for many years in their chemical plant in St Louis, and was an electrician among other things--I would guess this is salvage from there. It does not appear to have any particularly rare parts inside (the main active parts of the controller proper are two 741 op amps and an MCT2 opto-isolator), but I'm amused that it has switches for "clockwise/counterclockwise" (presumably stirring or pump of some sort) and "acid/base", both of which could be repurposed to amusing effect without relabelling, I think Smile The pots have nice big verniers on them too, though the range of values is on the small side.


The Chaos entries you mention Uncle is pretty interesting, I'd kind of like to see two meters (or three?) one for each axis (the potential third being the nonlinear out of one of Ian's boards that I have). I think that would be an interesting visualization. Any reason why you suggest using a switch and a fixed set of modules? I would think you could simply take an input and use a buffered mult to drive it and then you could run any signal you liked through it, probably with an attenuator on the front end. Which, now that I think about it, seems like a pretty good application of the other meter, actually, and fairly simple as long as I take precautions not to overdrive the meter etc. As far as it goes, since it's a voltmeter anyway, I may be able to simply repurpose all that behind the panel and get whatever protection is has built in anyway.


I have a few other irons in the fire, (not to mention big ole backlog) so this isn't likely to go anywhere soon, but it's an interesting thing to think on.
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JingleJoe



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PostPosted: Wed Nov 28, 2012 3:33 pm    Post subject: Reply with quote  Mark this post and the followings unread

Funny you should nmetion this as one of my latest devices has a meter in it, I bought loads years ago (they are one of my collections) and used a few in electronic devices. I've done more research into them scince then and plan to use some in synths I build Smile
They will look bloody amazing in anything they are used in. Very Happy

as suggested above I'd only suggest LFO, envelope or general CV level monitoring.

If you need any tips on using them, give me a shout, I know a few things about re-adjusting ranges.

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elmegil



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PostPosted: Wed Nov 28, 2012 7:11 pm    Post subject: Reply with quote  Mark this post and the followings unread

Great, thanks Joe Smile
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RingMad



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PostPosted: Thu Nov 29, 2012 6:50 am    Post subject: Reply with quote  Mark this post and the followings unread

JingleJoe wrote:
If you need any tips on using them, give me a shout, I know a few things about re-adjusting ranges.


Nice to see you back, JingleJoe! Maybe you could write a mini-tutorial on these things. I've salvaged a few but could never figure out what to do with them that would be really cool. Plus, I tend to go for the smallest enclosure possible, and there's never room for a meter.

James.
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JingleJoe



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PostPosted: Thu Nov 29, 2012 12:18 pm    Post subject: Reply with quote  Mark this post and the followings unread

I feel like I'm not qualified enough to write a tutorial Laughing but I am qualified enough to get these damn things working again after 60 years so god damnit I might just do that!
RingMad wrote:
Plus, I tend to go for the smallest enclosure possible, and there's never room for a meter.

James.

You need to get in touch with your inner 1940's mad scientist:

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RingMad



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PostPosted: Thu Nov 29, 2012 6:52 pm    Post subject: Reply with quote  Mark this post and the followings unread

JingleJoe wrote:
but I am qualified enough to get these damn things working again after 60 years...


Gee, I didn't know you were *that* old, JJ. Smile

James.
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JingleJoe



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PostPosted: Fri Nov 30, 2012 3:50 am    Post subject: Reply with quote  Mark this post and the followings unread

RingMad wrote:
JingleJoe wrote:
but I am qualified enough to get these damn things working again after 60 years...


Gee, I didn't know you were *that* old, JJ. Smile

James.

I think you're joking, but just FYI I'm 23, the meters are 60 years old Laughing therein lies a problem, because they are so old the coils often go open circuit, then you're fucked. Technical term for broken meters, that is Wink

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RingMad



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PostPosted: Fri Nov 30, 2012 8:32 am    Post subject: Reply with quote  Mark this post and the followings unread

JingleJoe wrote:
I think you're joking, but just FYI I'm 23, the meters are 60 years old Laughing


Yes, I was joking. It's just one of those sentences that could be read with that conclusion Smile.

But how can a coil go wrong? Wire's wire, no? It's not like caps which leak or the chemistry changes over time which affects its capacitance. Hmmm... anyway, none of my meters are that old, although I am pretty old.

James.
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JingleJoe



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PostPosted: Fri Nov 30, 2012 9:54 am    Post subject: Reply with quote  Mark this post and the followings unread

RingMad wrote:
chemistry changes over time

Acctually it is exactly that, some part might not have been insulated fully so it oxidises and breaks or some part of it might short circuit over time due to the slowly shifting pitch or never-quite-set resin used to seal the windings, or maybe part of the winding was allways weak (as that wire can be INCREDIBLY thin) and over time the current flowing through it, damaged it untill it broke one day like a fuse wire.
Very often there are thin coils of resistance wire which break and some meters even have copperoxide diodes which can go wonky over time.
The contacts to the coil can be a problem too, getting oxidised or blocked by dirt- by the way I'm talking about moving coil meters here, which many old ones are, including the two within arms reach of me Smile if you have to replace or re-align the coils, they are the hardest, most fiddly thing to fix, ever.

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Uncle Krunkus
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PostPosted: Mon Dec 03, 2012 4:56 pm    Post subject: Reply with quote  Mark this post and the followings unread

JingleJoe wrote:
if you have to replace or re-align the coils, they are the hardest, most fiddly thing to fix, ever.


I'll second that!
In fact, I wouldn't even try. The chances of successfully working on one without changing it's functionality are minimal. You can't really describe a coil meter as a solid state device. In fact any reasonably sensitive coil will have some movement in the windings. Time and power dissipation are it's worst enemies.

BTW Great to see you back Joe! Very Happy

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JingleJoe



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PostPosted: Tue Dec 04, 2012 12:03 pm    Post subject: Reply with quote  Mark this post and the followings unread

Uncle Krunkus wrote:
You can't really describe a coil meter as a solid state device.

In fact, I think it would be classed as electromechanical Surprised

Quote:

BTW Great to see you back Joe! Very Happy

Thankyou Smile it is great to be back.

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RingMad



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PostPosted: Wed Dec 05, 2012 5:26 pm    Post subject: Reply with quote  Mark this post and the followings unread

Ah yes, silly me... I forgot about oxidation. Wow, JingleJoe you know a lot about those meters and problems thereof!

Raising the question raised earlier by Neil Young: is it better to burn out, than to rust away?

All I can add is this quote from a Sonic Youth song: "I never gave a damn 'bout the meter man, 'til i was the man who had to read the meters, man."

James.
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JingleJoe



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PostPosted: Thu Dec 06, 2012 1:36 am    Post subject: Reply with quote  Mark this post and the followings unread

If you use them right, they shouldn't burn out so they will still technically suffer death-by-rust. Nevertheless, I support death by usage not age.
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