Where to get a high quality analog DC voltmeter? - Page 1
Forum section: electronics / beginners

author: dereksgc
author_rank: Newbie
timestamp: June 21, 2024, 03:29:49 pm
content: Hello, first post here. I'm working on a small radio project and I've got the genius idea of using an analog voltmeter as the frequency display. The tuning knob turns a dual potentiometer whose second range forms a voltage divider which is in turn read by the voltmeter to give you the indication of where you are tuned. I got a 15VDC analog meter and I replaced its built in series resistor to turn it into a 3.3V meter (as that is the voltage I'm working with). At first it worked very poorly because I didn't realize that an analog meter will load the 100k voltage divider too much, but that issue has been solved by adding a voltage follower with a high impedance input (currently a RPi pico, hopefully to be replaced by an opamp, that's besides the point now). However my main issue with the meter now is that the needle never seems to settle at the same place. If I go from the 0V marker to the 15V marker on the label and then back to 0V the needle will either land or 0, or at 0.1, 0.2, or below zero, etc. Tapping the meter helps settle the needle which suggests the issue is entirely mechanical inside the meter, which I guess is to be expected from a cheap Chinese "modern" one.My question is, where in the current age could I get a DC analog voltmeter that would have decent mechanical properties, as in a very well dampened and balanced needle that would at least have a *reasonable* error. I know things like this are to be expected with an analog meter but surely what I have is from the bottom of the barrel and there are meters that are higher quality than this. I'm not really bothered by the scale being non-linear. I've been thinking about buying one of the old analog multimeters as those are bound to have a higher quality mechanical meter as their main display and tuning its series resistance until it behaves like a 3.3V voltmeter, but I may be wrong and I don't want to end up with another borderline useless meter.Also, I did consider that maybe the meter's poor performance is because it was meant for 15V originally, so I did put in a boost converter to actually drive it with a 15VDC divider and while it did feel a bit more "responsive", the needle not wanting to settle in the same place was still an issue.

author: TimFox
author_rank: Super Contributor
timestamp: June 21, 2024, 03:39:43 pm
content: Surplus dealers in the US, such ashttps://www.surplussales.com/Meters/Index.htmlstill have decent d'Arsonval meters available, but the good ones (Simpson, Weston, Triplett, etc.) have become expensive (some around $100 USD).

author: BeBuLamar
author_rank: Super Contributor
timestamp: June 21, 2024, 03:47:32 pm
content: I don't understand what you want to do but why do you need an analog meter? Why a digital won't do? The Radio Shack analog meter with FET front end would give you high impedance input.

author: Gyro
author_rank: Super Contributor
timestamp: June 21, 2024, 06:14:04 pm
content: Quote from: BeBuLamar on June 21, 2024, 03:47:32 pmI suspect that the OP is intending at make a radio receiver. You can't use a simple digital frequency meter (I don't have a reference for the Radio Shack one) because the tuner local oscillator is offset by the IF frequency.

author: David Hess
author_rank: Super Contributor
timestamp: June 21, 2024, 07:12:54 pm
content: I would look for a taut band meter, and maybe one that has a mirrored scale. A good d'Arsonval movement meter will also meet your requirements.

author: dereksgc
author_rank: Newbie
timestamp: June 22, 2024, 10:50:43 am
content: Quote from: BeBuLamar on June 21, 2024, 03:47:32 pmI need it to be analog because I can simply print a new multi-scale label on a piece of paper and put it behind the needle, so it gives me rough indication of where I am tuned to based on the position of the tuning potentiometer. A digital meter would simply always just show 0-3.3V. I suppose I could just print a conversion table to go from the digital meter voltage to frequency depending on which band is selected but that wouldn't be as neat.Quote from: TimFox on June 21, 2024, 03:39:43 pmI am in Europe and I'm not aware of any surplus stores like that existing here, but I am now paying a lot more attention to people selling old analog multimeters. I didn't realize that they would come with a high impedance buffer in front of the analog meter, although it makes perfect sense.

author: dereksgc
author_rank: Newbie
timestamp: June 22, 2024, 10:51:29 am
content: Quote from: David Hess on June 21, 2024, 07:12:54 pmIs there anything I should look for on a meter that would give away it is using this kind of mechanism?

author: JohanH
author_rank: Frequent Contributor
timestamp: June 22, 2024, 11:09:36 am
content: There are lots of NOS Soviet meters on Ebay that you can get from eastern Europe, e.g. Ukraine and Bulgaria. Some of them have mirror scale and good mechanism. E.g. the М265М is one example, but rather large.

author: BeBuLamar
author_rank: Super Contributor
timestamp: June 22, 2024, 11:10:03 am
content: For 0-3.3V you can build an OP amp to give the meter high impedance input and also do the scaling.

author: Gyro
author_rank: Super Contributor
timestamp: June 22, 2024, 11:17:27 am
content: Try ebay. Search strings such as 'vintage meter', 'moving coil meter' and 'taut band meter' all bring up hits for me here in various styles or and ages, some very cheap.Looking down at the bottom of the scale of current sensitivity and accuracy class. Sometimes meters will indicate that they are taut band. If the top of the moving coil is visible, it easy to tell - a jeweled bearing meter will have a tiny adjustment screw at the center axis of rotation and a coiled hairspring visible, while a taut band one will just have a little copper looking leaf spring with a tiny blob of solder on it.Taut band isn't necessarily an indication of accuracy (or at least linearity) as they are cheaper to manufacture. They just don't have the danger of 'stiction' if the needle is moving very slowly, that youmightget with old jeweled bearing ones that been subject to drops or mishandling.Avoid anything with a non-linear scale as it will be moving iron or something more exotic like thermocouple.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: June 22, 2024, 11:41:28 am
content: Here is an example of a Fourdee PSM 37 FET 10 Meg input meter which I have, it has scales of .5 Volt and 2.5 volt and 10 Volt and others. It is a meter that was used by US Military. I think the schematic is in the attachment and it would not be hard to make a meter specifically for 3.5 volts from a good Soviet Movement. Most of the circuitry of these meters involves the Range Switch and ranging Resistors, which you do not need. This is a very accurate meter and works nicely and has a low voltage resistance function also.

author: tooki
author_rank: Super Contributor
timestamp: June 22, 2024, 11:43:26 am
content: Ummm… you can still buy new analog panel meters from distributors. No need to resort to new old stock hiding somewhere.I know for a fact that here in Europe, Distrelec carries a bunch of them, because I used one in a project recently and bought it from them. Nice Japanese-made product from Kyoritsu IIRC.P.S. If you buy a sensitive analog ammeter, you can then easily convert it to a voltmeter by using current limiting resistors. That’s what I did to make a 0-40kV panel meter — not a typical off-the-shelf part! 😂 I got a 0-100 μA meter and put 400Mohm in series. One can similarly convert an ammeter to nearly any voltage range.

author: Gyro
author_rank: Super Contributor
timestamp: June 22, 2024, 11:57:04 am
content: Quote from: tooki on June 22, 2024, 11:43:26 amI've got a 10kV panel meter that doesn't need any series resistors and doesn't pull any (DC) current. That's the wonder of ebay.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: June 22, 2024, 12:26:59 pm
content: There are hundreds of new meters on AliExpress just waiting for an application, Some even have the scale you are looking for.

author: tooki
author_rank: Super Contributor
timestamp: June 22, 2024, 01:27:33 pm
content: Quote from: Gyro on June 22, 2024, 11:57:04 amHow does that work?

author: Gyro
author_rank: Super Contributor
timestamp: June 22, 2024, 01:35:15 pm
content: It's an Electrostatic one. Worth keeping an eye open for (I have a 1kV one too [EDIT:https://www.eevblog.com/forum/metrology/characterising-and-electrostatic-voltmeter/).

author: RAPo
author_rank: Super Contributor
timestamp: June 22, 2024, 01:37:51 pm
content: Would aTekpower TP8250do the job?

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: June 22, 2024, 02:03:39 pm
content: I THINK the OP needs a high impedance meter. I do not think the Tekpower is high impedance, I did read the specs.

author: tooki
author_rank: Super Contributor
timestamp: June 22, 2024, 02:11:17 pm
content: Quote from: Gyro on June 22, 2024, 01:35:15 pmOh neat, I wasn’t aware of those!

author: Gyro
author_rank: Super Contributor
timestamp: June 22, 2024, 04:36:52 pm
content: You've reminded me that I should characterize it and add it to the thread (even though it will probably be at least 10 times harder!).

author: xvr
author_rank: Frequent Contributor
timestamp: June 22, 2024, 09:06:49 pm
content: QuoteIf this is the ONLY one reason to use analog voltmeter then simple combination of Arduino/RPiPico/etc + 7 segment display/LED/LCD/etc will give you MUCH more flexibility in what and how you can display (and cheaper) than any good analog voltementer.

author: BeBuLamar
author_rank: Super Contributor
timestamp: June 22, 2024, 09:50:11 pm
content: If you can post the voltage versu frequency I think I can try to make something.

author: CaptDon
author_rank: Super Contributor
timestamp: June 23, 2024, 01:10:17 pm
content: Your sticky meter problem reminds me of when purely mechanical altimeters transitioned into the jet age. Mechanical altimeters do indeed tend to be 'jumpy' when sitting on a shelf like at small F.B.O. airports. In a piston powered aircraft there was enough vibration for the altimeter to move smoothly. With the smoothness of the jet engines the altimeters again appeared as sticky or jumpy. The solution, a tiny little vibrator built inside the altimeter!! I remember a big selling point for meters years ago was "Two Jewels" and we thought "Wow, they must be the best"! Turns out they probably weren't.

author: Andreas
author_rank: Super Contributor
timestamp: June 23, 2024, 05:53:29 pm
content: Hello,with hydraulic control valves usually a "dithering" function, normally a low frequency (20-200 Hz) sine overlay over the average output current is added to avoid "slip stick" effects.Of cause this can also be achieved with a enough low frequency PWM actuation instead of a DC current output.with best regardsAndreas

author: enut11
author_rank: Super Contributor
timestamp: June 23, 2024, 09:33:11 pm
content: Here is a used taut band meter on eBay. Taut band=zero friction so always returns to the same point.Search for a used analog meter and look for a 'taut band' indication on the meter face.https://www.ebay.com.au/itm/164688683600?itmmeta=01J13G12VM5XXHCCS914AEHVSR&hash=item265835e250%3Ag%3ALZoAAOSwa5RgFQu0&itmprp=enc%3AAQAJAAAAwPJLzjQ%2FyH2bZyB5g6p%2F6mkRv5AWGBTSUaO%2FpGi4lBl5pREOiQDLD1XiiLaON8VGR5WHdBuIBZ%2B%2Bg%2B%2Bo%2BY21EiRq1QaDz50Ujz4WrTLmoTjnpgmx1ORh4XkGgM%2BmFmgHa38YVfhVl7%2FKdCvk3imaRIksKTDbYftU6lgbm%2BHw7WrZ9F64ixX4096JYPIrEYfW8jQmfy4JAMkcoTiNwm7D6BHwxcM46bcT9vnyUAgK6Xd9jyUx95yxTOGqcsadAOoN8A%3D%3D%7Ctkp%3ABk9SR_6thPCIZA&LH_ItemCondition=3000

author: SteveThackery
author_rank: Super Contributor
timestamp: June 23, 2024, 10:12:21 pm
content: Quote from: Andreas on June 23, 2024, 05:53:29 pmExactly what I was going to say: "jiggle" the meter electrically rather than mechanically (which I think would be a bit noisy). It basically means imposing a low AC voltage on top of the DC voltage. You will need to experiment with the voltage and frequency - we don't have enough information available to guess what those would be.

author: SteveThackery
author_rank: Super Contributor
timestamp: June 23, 2024, 10:16:28 pm
content: Quote from: xvr on June 22, 2024, 09:06:49 pmI think you are missing the point. This is about COOL! An analogue meter showing the receiver frequency is so much cooler than a crappy 7-segment or other digital readout. Analogue is beautiful, digital is ugly; analogue is characterful, digital is bland. Analogue looks period, digital doesn't. 😉

author: David Hess
author_rank: Super Contributor
timestamp: June 24, 2024, 12:43:54 pm
content: Quote from: dereksgc on June 22, 2024, 10:51:29 amIt will have to say so in the description.

author: BeBuLamar
author_rank: Super Contributor
timestamp: June 24, 2024, 02:18:53 pm
content: Quote from: SteveThackery on June 23, 2024, 10:16:28 pmI don't think that what the OP wanted but if he does the best way is to have a company like Simpson make him one with custom scale. Simpson and other companies do offer custom scaling options. Then you use a buffer amp to give the meter high input impedance as well as the ability to calibrate. Of course it's lot of money.

author: jzx
author_rank: Regular Contributor
timestamp: June 24, 2024, 06:08:55 pm
content: You can buy an analogue multimeter.

author: BeBuLamar
author_rank: Super Contributor
timestamp: June 24, 2024, 06:49:28 pm
content: Quote from: jzx on June 24, 2024, 06:08:55 pmIt would be difficult to replace the scale of an analog VOM and also make it not usable as a multimeter any more.

author: SteveThackery
author_rank: Super Contributor
timestamp: June 24, 2024, 08:21:33 pm
content: Quote from: BeBuLamar on June 24, 2024, 02:18:53 pmYou can do it for free very easily. I've done it myself. You just design a new scale in a drawing app (I used Visio), print it out onto glossy or satin-finish photo paper, cut to size and put it in the meter as a replacement for the original dial.I've made a couple of watch dials like that, too. I've got a Russian watch with a 24-hour dial, and it has midnight at the top, midday at the bottom. That seemed unintuitive to me, so I made one with noon at the top, midnight at the bottom and shaded the bottom half to represent night time. Sorry - way off topic. 😄Anyway, I would use the meter the OP already has, print a new dial and add some low voltage dithering to overcome the stiction.

author: Gyro
author_rank: Super Contributor
timestamp: June 24, 2024, 08:43:40 pm
content: You can use MeterBasic, it's free for a single scale...https://www.tonnesoftware.com/meter2.html