Analog meter VS a DMM? - Page 1
Forum section: electronics / beginners

author: etstudent
author_rank: Regular Contributor
timestamp: October 23, 2012, 02:38:26 am
content: I'm waiting for my analog meter to arrive before starting my next set of challenges. The next ones are linear integrated circuits. You can't use a DMM, it say specifically not to, and in bold letters to use an analog meter only. What are the main differences between the two, and are there circumstances an analog meter is to be used only over a DMM? Thanks for the info I'm sure you guys have.

author: FenderBender
author_rank: Super Contributor
timestamp: October 23, 2012, 03:32:18 am
content: I'm no expert myself BUT an analog meter should give you better sensitivity to small changes in (whatever you are measuring) because as it says...it's analog...there's no ADC to turn it into a digital number. An analog meter can read an infinite amount of values in a range...technically.I'm not sure exactly what you are using it for but that's part of the reason to use an analog meter over a DMM. However, most of the time a DMM is your best friend.Also, what analog meter did you get? Even a mid-priced analog meter doesn't always cut it.

author: ejeffrey
author_rank: Super Contributor
timestamp: October 23, 2012, 04:48:49 am
content: Analog is easier to see quantities that are changing in the few Hz range. Digital displays become useless when they are changing every update, for instance if a quantity is flickering between 6.99 and 7.00 is very hard to read, especially if the meter has a high update rate. Most DMMs have an averaging mode to provide a more stable reading. With an analog meter on the other hand, you can see both the average value and notice that the needle is oscillating back and forth.Traditional analog meters are much less ideal than digital meters. Their voltage modes have lower impedance, their current modes have higher impedance, and their resistance modes have less control over the injected current. There are analog meters with FET preamps that solve some of these problems.Analog meters are more delicate. Overcurrent through the movements coil can damage it, so you have to be careful to make sure you are on the right range. They are also more susceptible to mechanical shock.Analog meters require more care by the user to get an accurate reading. You need to use the mirror scale to eliminate parallax error and even then you get at best resolution equivalent to a few hundred counts. A careless user can have much worse.

author: poptones
author_rank: Frequent Contributor
timestamp: October 23, 2012, 05:42:35 am
content: I don't even have a digital meter right now. And a very good analog meter can be quite affordable.http://www.ebay.com/sch/i.html?_trksid=p3984.m570.l1313&_nkw=simpson+260&_sacat=0&_from=R40

author: etstudent
author_rank: Regular Contributor
timestamp: October 23, 2012, 11:51:26 am
content: Thanks guys, I forgot about analog meters being better with fast changing voltages. Interesting info guys, thanks a lot.

author: SeanB
author_rank: Super Contributor
timestamp: October 23, 2012, 03:22:28 pm
content: I would guess forcing them to use an analogue meter is to reinforce the idea that precision is not just a digital idea, but that it is an analogue thing, and as well to teach about measuring accuracy and the importance of observer training and bias in getting an accurate reading.

author: hepcat
author_rank: Newbie
timestamp: March 31, 2013, 11:31:25 pm
content: An analog meter would most likely be better for testing the resistance of contactor and relay contacts, because its short circuit current flow is substantially higher than a DMM. As an example, my Agilent U1272A puts out about 640 microamps, as measured by my Fluke 189. According to the data sheet, a Simpson 260 puts out 125 milliamps on the RX1 scale. There are some situations, such as relay contacts, where you actually want to 'stress' the connection. A DMM, with its miniscule current flow, may be harder pressed to give a true and definitive reading in such situations.Regards,Jason

author: Unknown
author_rank: Unknown
timestamp: March 31, 2013, 11:50:14 pm
content: This highly depends on your definition of a 'true and definitive reading'. Is 125 mA a good test for a relay in a test equipment switching matrix, for example? Or a telephone exchange (in the days that they still used relays)? Is it a good test for a relay switching a large motor that draws tens of amps?Dry circuittesting is actually a fairly common test for connectors and switches, since it measures the oxides and contamination that might form. Testing at 125 mA is likely to remove the contamination, making the test useless.

author: w2aew
author_rank: Super Contributor
timestamp: April 01, 2013, 01:39:30 am
content: As stated in earlier replies, analog meters are very nice in a couple of instances... It is much easier to watch the movement of an analog meter when you are adjusting or tuning a circuit parameter. I used on in my PLL video and the video on using diodes as switches. It's much easier to watch a meter move up/down vs. trying to watch digits increment up and down.Also, the meter movement, due to its inertia, will tend to filter signals that are wiggling about.They are great for these circumstances when a relative reading is helpful, rather than a precise, accurate value. For the latter, a DMM is generally better.In my lab, I'll always have both.

author: madshaman
author_rank: Frequent Contributor
timestamp: April 01, 2013, 03:42:05 am
content: Quote from: w2aew on April 01, 2013, 01:39:30 amThat being said, who makes good analog meters and who makes bad ones?

author: Spawn
author_rank: Frequent Contributor
timestamp: April 01, 2013, 04:18:18 am
content: Gossen make good ones and top of the range model is around 900USD:http://www.gossenmetrawatt.com/english/produkte/analogmultimeters.htmand bad ones... I think there is a lot bad ones out there. Just stay with a known name and you will be good. It does not have to be new either.I got 2 analog meters last year, not new they are 38 years old now but still working nice:https://www.eevblog.com/forum/reviews/philips-multimeter-pm2505-teardown/

author: w2aew
author_rank: Super Contributor
timestamp: April 01, 2013, 04:42:53 am
content: Quote from: madshaman on April 01, 2013, 03:42:05 amI love my old Simpson 260. Standard in the industry for 30-40? years.

author: rsjsouza
author_rank: Super Contributor
timestamp: April 01, 2013, 11:27:53 am
content: Another use that I think VOMs are unbeatable is to find the polarity of the windings in unmarked transformers - the coil movement is really subtle but clearly indicates if it is going above or below zero. Something that is very difficult to see in a DMM, even with the bargraph.

author: robrenz
author_rank: Super Contributor
timestamp: April 01, 2013, 12:44:29 pm
content: Quote from: rsjsouza on April 01, 2013, 11:27:53 amPlease explain, I didn't know transformer windings had polarity.

author: rsjsouza
author_rank: Super Contributor
timestamp: April 01, 2013, 01:57:29 pm
content: Well, "polarity" is how I learned, but it may not be the most accurate term in English.It is simply the relative direction of the windings of a transformer between primary and secondary, or sometimes multiple primaries. The page 7 ofthis documentexplains a bit more.As a more practical example, some dual-voltage transformers have two primary coils that must be connected in parallel (if using 110~127V) or in series (if using 220~240V) - however, if you connect the two coils in reversed "polarity", nothing comes out of the other end.This other linkillustrates this and other cases.To quickly find the relative direction of the windings, you simply put the VOM in parallel with one winding, and "scratch" the other winding in the terminals of a DC battery (check the "ASCII art" below). If the VOM deflects positively, then you know the Battery + and the VOM + are in phase. If it deflects negatively, then they are reversed.[VOM +] ------- | || | |C | |110V C | |Primary C | | ---------C | | || | | C[VOM -] ------- | | C| | C Secondary[Battery +] ------- | | C| | | CC | | C110V C | | |Primary C | | ---------C | || | |[Battery -] ------- | |

author: robrenz
author_rank: Super Contributor
timestamp: April 01, 2013, 02:08:21 pm
content: Thanks, I always like learning something new.

author: rsjsouza
author_rank: Super Contributor
timestamp: April 01, 2013, 03:05:38 pm
content: Quote from: rsjsouza on April 01, 2013, 01:57:29 pmActually, I should have clarified something: "If the VOM deflects positively when the battery is connected and negatively when the battery is disconnected, then you know the Battery + and the VOM + are in phase."

author: Tepe
author_rank: Frequent Contributor
timestamp: April 01, 2013, 03:18:34 pm
content: Quote from: Spawn on April 01, 2013, 04:18:18 amI've had this one since the late 70s:

author: madshaman
author_rank: Frequent Contributor
timestamp: April 01, 2013, 09:49:40 pm
content: Quote from: w2aew on April 01, 2013, 04:42:53 amThanks for the recommendation, and also those of others!When I started as a kid, all I had was a hand me down analog meter (whose brand I don't even remember) and an ancient health kit scope built out of tubes from my grandfather.Don't have an analog meter anymore, my childhood equipment and projects are long gone due to unfortunate circumstances, but I think I'll pick one up!

author: nanofrog
author_rank: Super Contributor
timestamp: April 01, 2013, 10:14:01 pm
content: Quote from: madshaman on April 01, 2013, 09:49:40 pmYou might want to take a close look athttp://simpson260.com/for buying a used one, as it sorts out the differences between the revisions and models.Simpson still makes them though, so there's that option as well.

author: ivan747
author_rank: Super Contributor
timestamp: April 03, 2013, 02:36:50 am
content: I still don't understand what are the advantages of an analog multimeter vs. a digital multimeter with a fast updating bar-graph display. And the second thing I don't understand is why are they restricting students only to use almost obsolete, limited technology with low input impedance.

author: CraigHB
author_rank: Regular Contributor
timestamp: April 06, 2013, 08:44:30 pm
content: I was going to say the same thing. I have a high end DMM that has a bar graph as well as a digital display. It seems to be able to do the same thing an analog meter can.

author: w2aew
author_rank: Super Contributor
timestamp: April 06, 2013, 11:02:43 pm
content: Quote from: ivan747 on April 03, 2013, 02:36:50 amA couple of reasons they want you to use an analog meter.- the analog meter movement has 'infinite' resolution, no discrete segments of a bar graph.- the bar graph doesn't work real well when watching a parameter that crosses an auto-range boundary.From an educational standpoint, the analog meter forces you to THINK more about what your circuit is doing. You need to think about the polarity of what your measuring, and what approximate voltage level you expect to see. A modern, auto-ranging DMM eliminates most of the thinking part except picking the right mode.

author: CraigHB
author_rank: Regular Contributor
timestamp: April 06, 2013, 11:14:31 pm
content: Quote from: w2aew on April 06, 2013, 11:02:43 pmTrue on the first point, but it may be hard to notice the movement in a needle that would represent one bar segment to the next. Such small deflections can be hard to see.On the second point, I can set my meter to range manually which would eliminate any change in scale due to a range shift.In terms of educational value, I can see where an analog meter might be desireable, but practically, I don't see a huge advantage over a meter that provides a graphical representation of a gauge.

author: ivan747
author_rank: Super Contributor
timestamp: April 07, 2013, 12:11:01 am
content: Quote from: CraigHB on April 06, 2013, 11:14:31 pmMy thoughts exactly. And considering good quality analog multimeters can cost as much as their digital counterparts, I think they are losing their place.About the infinite resolution: I don't think it's going to be easy to see a 5mV change on a 5V scale, that's 0.1% of the full scale. Assuming the needle can swing 135 degrees. That is 135/360=0.375*100=37.5% of a full circle. Let's assume the needle is 5cm long. The radius of out circle is 5cm. The total perimeter of the arc that forms the circle is 5*2*pi= ~31.41. The length of our 135 degree arc is 0.375*31.41= ~7.779. That is the distance the needle moves when you apply the maximum voltage your range allows. We said earlier that on a 5V range, a 5mV change is 0.1% or the full scale, so: 7.779*0.001=0.00779cm or 77.9µm (0.0779mm). That's 3 mils, the same size of a pixel in an iPhone Retina display or as small as board manufacturers go on trace width.

author: w2aew
author_rank: Super Contributor
timestamp: April 07, 2013, 02:43:41 am
content: Agreed, certainly there are limits to how small of a change is noticable with an analog movement, but it is generally better than the resolution of a segmented bar-graph. Also agreed that manually selecting a range on a DMM will avoid the range changing on the sweep - but this implies a slightly more educated user as opposed to a student.One more minor advantage with the analog meters, under some circumstances the inertia of the meter movement can provide a bit of dampening of a noisy measurement that might be difficult to observe on a DMM.Of course, most of the time I'll use my DMM, but I occasionally find good use cases for my old 260 VOM. And, I fully agree that students should be taught how to use BOTH and to understand the advantages of each.

author: rsjsouza
author_rank: Super Contributor
timestamp: April 07, 2013, 03:38:59 am
content: Agree with w2aew in all accounts. Regarding resolution, comon bargraphs are only 40 or 60 segments and do not have the natual filtering of the mechanical needle - something needed in the example I sent before.

author: Resistoid
author_rank: Contributor
timestamp: April 07, 2013, 08:57:34 pm
content: You asked about good analogue meters. Over in the UK, at least, the Avometer was considered to be the "Rolls-Royce" of these devices:http://www.megger.com/uk/Products/ProductDetails.php?ID=302&Description=avometer%20model%208More details here:http://www.megger.com/common/documents/MOD8_MK7_DS_en_V11.pdf- You can find various models / mark numbers on Ebay at quite reasonable prices these days.Resistoid.

author: ivan747
author_rank: Super Contributor
timestamp: April 08, 2013, 02:44:03 am
content: Modern high-end multimeters like the Agilents Dave has have a low pass filter option, so you can overcome noise in your measurements. As far as I know DMMs take several samples and average then before displaying so that, combined with the LPF and the analog bargraph gives you all you needed in an analog meter. There's also a low impedance mode if you need to get rid of stray voltages induced in large coils and such.And by the way, no one's going to rely on the analog bar graph resolution to make measurements, you use the digital display. If noise is an issue, turn in the LPF.Sure, these are more expensive than used analog meters, but so are high-end scopes vs. used CROs. High-end scopes imitate the CRT of an analog scope with intensity grading and have a lot of added benefits, just like high-end DMMs vs. analog meters.

author: vk6zgo
author_rank: Super Contributor
timestamp: April 09, 2013, 02:43:49 pm
content: Although bargraphs may be able to imitate analog meters,they usually have a lag,so that adjusting a voltage or current value becomes more difficult.For "peaking" tuning or similar,I usually use an Oscilloscope,either reading signal levels directly,or if there is an associated DC voltage change,as a DC voltmeter.

author: KJDS
author_rank: Super Contributor
timestamp: April 10, 2013, 07:32:27 pm
content: Quote from: Resistoid on April 07, 2013, 08:57:34 pmEarlier today I tested three AVO 8 meters. I tweaked a power supply until the AVO read 3V exactly. I also had a 6.5 digit Keithley 2015THD measure the same reading. The 2015 showed 2.998V, 3.006 and 3.008VThey really are a fine bit of kit. I think there's about 2mV resolution on the 3V range.

author: Resistoid
author_rank: Contributor
timestamp: April 13, 2013, 10:45:04 pm
content: @ KJDS - agreed, excellent gear. It's a real pity Megger have ceased production.So far as I recall, the Model 8 Mark VII was being sold new for about £700, (or £900 if you bought from RS Components), before the end. - Now secondhand ones can be had much more cheaply.I own a couple of Model 8 Mark Vs and wouldn't part with them for anything.Resistoid.

author: NiHaoMike
author_rank: Super Contributor
timestamp: April 14, 2013, 02:05:31 am
content: Quote from: hepcat on March 31, 2013, 11:31:25 pmAt such low resistances, you'll really need a 4 wire measurement. It's possible to make an analog meter with 4 wire resistance measurement, but in practice, I've only seen digital meters with 4 wire resistance measurement.Technically, a digital bargraph can respond faster than an analog meter since it doesn't have inertia. The low impedance is useful in a few cases, but they make digital meters with that as well. The auto ranging on digital meters can be annoying, but any good meter lets you turn that off.An advantage analog meters still have is that they don't need a battery to measure voltage or current. While that's possible for a digital meter, I have not seen one that does. (That would obviously make it no longer high impedance, so add a switch to disable that feature and use batteries just like a normal meter.)

author: vk6zgo
author_rank: Super Contributor
timestamp: April 14, 2013, 03:26:00 am
content: Most bargraphs I've seen "dither"when confronted by a signal which is part way between two steps.Obviously,they can be, & are, made in forms that do better,but not commonly.Or the "bargraph" can be be replaced with a simulated analog meter.Top end Amateur Radio Transceivers have digital display based "S meters" which are indistinguishable from a real meter---they even have the same inertia characteristics as specified for a mechanical meter in the same service.But these are part of a generally very sophisticated device,& are not cheap!High impedance isn't just available with DMMs--Old style VTVMs,& the later FET based meters have similar input Z,as does an analog 'scope (with a x10 probe).As I implied before,such a 'scope in the DC input mode,& with the triggering set to"AUTO,makes a useful large scale DC voltmeter.Back in the day,4 wire measurement was done with analog meters,as they were the only game in town!

author: madshaman
author_rank: Frequent Contributor
timestamp: April 18, 2013, 08:10:50 pm
content: Quote from: nanofrog on April 01, 2013, 10:14:01 pmThanks man! Been distracted from the forum by the fairer sex for a bit (I know, for shame, but she digs my lab anyway ;p). I'm halfway committed to getting a new Simpson 270-5RT with leather carry case.