|WikiProject Electronics||(Rated Start-class, Mid-importance)|
|WikiProject Electrical engineering||(Rated Start-class, Mid-importance)|
Article needs quite a bit of work
This really isn't all that informative. I would want to see alot more details on how DVM's work... I made one at one point, but I don't think I know enough that I should be editing this. I originally came looking for information on high impedence measurements - hopefully done with a low impedence DVM. It looks like it's possible, but requires a buffer which I will not have time to work out. Simon.p.hastings (talk) 06:02, 8 July 2010 (UTC)
- What, specifically, were you looking for? The DVM section does point at A to D converter. There's lots of techniques for making electical measurements, but this article is about one instrument, not a tutorial on electrical measurement techniques. --Wtshymanski (talk) 13:12, 8 July 2010 (UTC)
- I didn't mean that the article should cater to my specific purpose of coming, but the information I wanted is fairly basic - what would the typical electrical layout of a digital voltmeter look like. Some examples of problem I see with this article at the moment: The section of oscilloscopes needs reworking or should be removed. As you say, this is not an article on voltage measurement techniques, and so an oscilloscope article really is seperate. If it should remain in - please be clear that you are refering to an analog 'scope. Most people will not see those anymore, although I'm hardly an expert on the topic. The DVM section also needs reworking. The article should probably focus on them - analog devices are rarely used in practice, so why is there just 3 or 4 lines on them, and so much on the other stuff? I understand that you point to the basic principle of the integrating circuit, but the specific implementation is what I was interested in when I came here. Also, claiming that a 10 MOhm impedence is universal without citation is just plain dangerous. If people don't have a citation for that, it really needs to be corrected. I'm sure I've seen/heard of 1 MOhm and much higher impedence devices. Simon.p.hastings (talk) 02:30, 9 July 2010 (UTC)
- 1 megohm is less than 10 meg ohm. No-one on the Wikipedia ever says something is 'universal', the article says 'generally' 10 megohms. Are you aware of models of DMM that don't have 10 meg input impedance, if so, they must also come with their own models of hv probes, which generally work with 10 meg inputs (my Hall and Horowitz is packed away at the moment). The scope measurement of voltage is independent of analog or digital scope, agreed, not relevant to voltmeters. The article is about voltmeters, not just one type of voltmeter, so over-emphasis on one type is inappropriate. What do you mean by "layout" of a DVM? Physically, there's a myriad of choices, electronically they all pretty much have an input network, a/d converter, display (and sometimes a microcontroller, etc.). Would a block diagram help? --Wtshymanski (talk) 03:16, 9 July 2010 (UTC)
- I think a block diagram would be helpful - and citations to appropriate references outside of WP if there are many such designs. That you can't say something general about them is no reason to not provide examples of design choices one might see made. And while an emphasis on one type is inappropriate, I think the section needs expanding in either case. A couple extra sentances on the topic of impedance of the voltmeter may also be helpful. A brief search on wikipedia turned up plenty of DVM's with impedances both below 10 MOhm and above it. I think it's fair to say that 10MOhm is common, and perhaps the majority, but there are markets for higher value meters(For cases exactly like mine) - as well as a myriad of do it yourself solutions for constructing them, as well as I suspect a pile of bargain-bin meters with lower impedance. And of course, external probes change this situation extensivly. In any event, I'm not trying to argue for specific changes - my original point was that the section as it is needs work. In the time we've been typing these messages, the changes could easily have been made. You seem to know more about it than I - and my grammer is not good for this sort of editing. Can we agree it needs expanding, and I leave it to you as you see fit? Simon.p.hastings (talk) 03:38, 9 July 2010 (UTC)
- Grammar is the least of a Wikieditor's worries; put something up and within minutes someone will be fixing "that" and "which" and un-splitting your infinitives. Unfortunately, Wikipedia editors don't work on assignments - if you see an omission in the article, fix it, and be bold!. Saying an article is no good is no help to editors...be specific, and don't be afraid to put in additions of your own. --Wtshymanski (talk) 12:05, 9 July 2010 (UTC)
Drop in voltage
Hello, can someone add how to compute the drop in voltage when we add a voltmeter ? It would be very nice for me.--Youssef 15:37, 14 July 2005 (UTC)
- A voltmeter is basically a resistance in a circuit that draws a small current. Adding that resistance during a measurement will interfere with that circuit, but if that resistance is very high then that interference can be neglected. Voltmeters can be rated as so many Ohms per Volt. 220.127.116.11 (talk) 14:05, 20 July 2016 (UTC)
Could someone explain how it is possible to convert a current meter to a volmeter via a resistance?
.......VOLTMETER>>>>> Why is a voltmeter connected in parallel in a circuit? BUBBLES
Because if it were connected in series the current would flow through the voltmeter and you would get the voltage drop due to the resistance of the voltmeter, not the circuit. eg. say you had your voltmeter connected in parralel over a switch and were measuring votlage applied through the switch. When closed the current would take the path of least resistance, this being the switch which has no resistance and therefore the voltage drop reading is zero. If the switch was open the current would be forced to travel through the voltmeter which has very high resistance and the reading would be that of the applied voltage.
DVM -- Can anyone tell me what the 4th connection point is on a Digital Volt meter and how it is different than the DVM that only hast 3 connections.
I was redirected here from moving coil meter which I need to illustrate another article...how about a d'Arsonoval movement diagram? I know, I know...if I want one I have to draw one....--Wtshymanski (talk) 17:00, 22 November 2007 (UTC)
Major changes recently made?
Does anyone know why the most recent changes were made? They look like the new page must be an old revision... The changes were made anonymously. Comment? The diff takes away 2600 lines! —TedPavlic | (talk) 19:15, 15 October 2008 (UTC)
- It was vandalism. Revert it. I've tried to put the missing text back as it should have been, hopefully without missing any good edits made in the last month. A good rule of thumb is that if you see a large decrease in article size after an anon IP has edited, check to see if it should be reverted - these are rarely positive edits in my experience. --Wtshymanski (talk) 16:01, 10 November 2008 (UTC)
about the class of the instrument
the page should include some discussion about the definition of the concept of "class", related to error specifications
The explanatory illustration
Sorry, but this is quite different from reality, to the extent of being misleading. Please see my comments on the Talk page for ammeters. I mean no personal offense, though.Nikevich (talk) 08:17, 30 September 2010 (UTC)
- Could you explain what's misleading? The current illustration looks pretty much like every textbook picture I've seen, and would allow our proverbial bright 12-year old to identify all the parts of a meter movement he/she was busily taking apart. Unless you're worrying about which way the coil is wound! --Wtshymanski (talk) 15:26, 30 September 2010 (UTC)
Technicalities about what a voltmeter really measures
First of all, normally a voltmeter does not measure differences in electrostatic potential, but rather in electrochemical potential of electrons a.k.a. Fermi level . There are some subtleties here with thermoelectric effect, band bending and so on where this is important.
- Yes. It measures differences in electrostatic potential. Andy Dingley (talk) 21:00, 25 May 2013 (UTC)
- Well, think about it this way: consider a piece of copper wire. What point do you choose to represent its electric potential: right next to the copper nucleus, or half way between neighboring nuclei, or in the points furthest from any nucleus? These places can differ in electrostatic potential by hundreds of volts, and yet when I attach a voltmeter (no matter how sharp my voltmeter's probes are) I measure zero volts on the wire. --Nanite (talk) 09:51, 26 May 2013 (UTC)
- This is an encyclopedia. Its goal is to explain concepts to an audience, at a level appropriate to that audience. This is a hard task, as we don't know the audience and their level of prior knowledge. However it's a reasonable bet that those looking for information on a simple voltmeter are unlikely to be thinking in terms of Fermi levels. Andy Dingley (talk) 12:48, 26 May 2013 (UTC)
- One could also say that any current measuring device is an extremely low resistance plus a voltage measuring device, measuring the voltage drop across its own resistance. This doesn't aid to anyone's understanding. Jeh (talk) 23:18, 20 July 2016 (UTC)
VTVM and FET
For anyone looking to add examples to this section, VTVms are fairly common (Hickok, RCA, HP, and others). FET examples seem to usually be called field-effect meters, and Sencore is an example. It may also be of interest that a Field Effect meter can measure resistance in circuit. — Preceding unsigned comment added by 2601:200:4203:91D2:99B2:1F8E:55C9:8835 (talk) 01:00, 2 March 2016 (UTC)