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Registered Member #3766
Joined: Sun Mar 20 2011, 05:39AM
Location:
Posts: 624
Hey all, I need to get 3 AC voltmeters, 0-15 volts, 3 AC voltmeters, 1-110V, 3 AC ammeters, 0-5A, 3 DC voltmeters, 0-15 volts, and 3 DC ammeters, 0-5A.
And I would like to get these without going broke. And I want them to match visually by type, not ALL of them(unless it's cheap), I just want the AC voltmeters to match, and the DC voltmeters to match, and etcetera.
Does anybody have any clue as to how to get these cheap? The cheapest I can find online is $15 a piece, so new is obviously not the way to go, since I need 15. That is $125. Not happening. Thoughts?
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Wouldn't a switching scheme of some sort enable you to use fewer meters?
As for finding matching moving coil panel meters of good quality, I'd suggest looking for ebay sellers in eastern Europe - Latvia, Lithuania, Bulgaria, Romania - where large stocks of technical inventory were abandoned after the collapse of the Soviet empire.
Even so, once freight charges have been added, you must not expect to get your 15 meter movements for pennies.
Economics has always been central to engineering design, so you must first decide your budget for this project, and then work out how your goals can be achieved within these financial limits.
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
If I needed 15 identical meters I'd look into what was involved in making them.
The setup costs will be the same for one as for 15.
Start winding some coils, get a pack of 30 identical magnets, and see what happens (use a DMM to calibrate them)
(I stripped a moving coil meter down once, there isn't that much involved)
I appreciate that you need 5 different types of meter, but this can be achieved using resistors and diodes (I think). It could be quite a worthwhile little project.
EDIT: If digital meters will be suitable, there are chips available, and circuits online. 15 LCD's or whatever shouldn't cost too much.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
Ash Small wrote ...
If I needed 15 identical meters I'd look into what was involved in making them.
The setup costs will be the same for one as for 15.
Start winding some coils, get a pack of 30 identical magnets, and see what happens (use a DMM to calibrate them)
(I stripped a moving coil meter down once, there isn't that much involved)
I appreciate that you need 5 different types of meter, but this can be achieved using resistors and diodes (I think). It could be quite a worthwhile little project.
EDIT: If digital meters will be suitable, there are chips available, and circuits online. 15 LCD's or whatever shouldn't cost too much.
Yeah but their pretty precise engineered devices. I dont know about building them, id go with LED or LCD's then theyll be the same and cheap.
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
Proud Mary wrote ...
Ash Small wrote ...
If I needed 15 identical meters I'd look into what was involved in making them.
The setup costs will be the same for one as for 15.
What, the cost of a light engineering factory once you've finished your apprenticeship as an instrument maker?
A pillar drill should be sufficient. Magnet 18 says he has one in this thread:
and that he has access to other tools.
A moving coil meter only has one moving part, the coil, usually pivoting on a pin. (I believe some have a return spring, similar to a watch spring, but other types of spring should work, with a suitable tension adjuster (nut and bolt, for example). Some, I believe just use gravity)
You basically 'tune' it by altering the number of turns on the coil, altering spring tension, or by 'biasing' with resistors (if that is the correct terminology.)
As Patrick points out, solid-state may be simpler, depending on personal preferance and ability, but once you devise a suitable pivot mechanism (pin, sharpened at both ends, between two centre-popped plates, separated by nuts, bolts and washers) the rest is just basic electro-magnetic theory and epoxy, etc.
It would cost pennies (or cents, depending on location)
Print off the graduated faces on a printer using a CAD or graphics package, and cannibalise some old CD cases for the windows.
Care obviously needs to be taken when positioning the magnets and epoxying them in, but final calibration can be done by altering number of windings, spring tension and biasing resistors if required.
Hardly complicated!
Rolling your own means YOU have TOTAL CONTROL over quality, accuracy, etc, limited only by what you use to calibrate it against.
( a better approach may be to mark off the graduations by hand, while comparing with a DMM or whatever)
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Ash Small wrote ...
Proud Mary wrote ...
Ash Small wrote ...
If I needed 15 identical meters I'd look into what was involved in making them.
The setup costs will be the same for one as for 15.
What, the cost of a light engineering factory once you've finished your apprenticeship as an instrument maker?
A pillar drill should be sufficient. Magnet 18 says he has one in this thread:
and that he has access to other tools.
A moving coil meter only has one moving part, the coil, usually pivoting on a pin. (I believe some have a return spring, similar to a watch spring, but other types of spring should work, with a suitable tension adjuster (nut and bolt, for example). Some, I believe just use gravity)
You basically 'tune' it by altering the number of turns on the coil, altering spring tension, or by 'biasing' with resistors (if that is the correct terminology.)
As Patrick points out, solid-state may be simpler, depending on personal preferance and ability, but once you devise a suitable pivot mechanism (pin, sharpened at both ends, between two centre-popped plates, separated by nuts, bolts and washers) the rest is just basic electro-magnetic theory and epoxy, etc.
It would cost pennies (or cents, depending on location)
Print off the graduated faces on a printer using a CAD or graphics package, and cannibalise some old CD cases for the windows.
Care obviously needs to be taken when positioning the magnets and epoxying them in, but final calibration can be done by altering number of windings, spring tension and biasing resistors if required.
Hardly complicated!
Rolling your own means YOU have TOTAL CONTROL over quality, accuracy, etc, limited only by what you use to calibrate it against.
( a better approach may be to mark off the graduations by hand, while comparing with a DMM or whatever)
If you have the skill, know how, and facilities to make, for example only, a pocket watch out of metal stock, you might very well be able to make an accurate moving coil meter, but who can say?
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
Proud Mary wrote ...
If you have the skill, know how, and facilities to make, for example only, a pocket watch out of metal stock, you might very well be able to make an accurate moving coil meter, but who can say?
It's around 35 years since I stripped one down and repaired it (when I was 12 or 13), but I remember it was very simple.
If I was Magnet18, I'd get one, even a non-working one, strip it down, and have a look at what's involved.
Maybe the simplest way to settle this 'debate' would be for me to make one and post details in the 'projects' thread?
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Where to procure meters?
