Talk:Electrometer

untitled section

Does it measure electric charge or electric field strength? - Omegatron 23:20, May 31, 2005 (UTC)

It responds to repulsion and attraction of charged objects of a particular shape immersed in a particular dielectric such as air... so it measures their shape, and their charge, and the surrounding e-field, and the voltage between them, and the characteristics of the dielectric! For example, we can build an electrometer-based field-strength meter. Or instead change things slightly and build a voltmeter, or a charge meter, or a meter which measures the dielectric constant of a substance. Analogy: we can use a coil/magnet d'arsonval meter movement to measure current or instead to measure magnetic field strength.--Wjbeaty 00:59, August 11, 2005 (UTC)

Temp Home for 'Valves'

Moved para on valves here temporarily until we decide how and if it fits into this article. Light current 11:11, 13 August 2005 (UTC)

Valves

The term is also used to refer to a special type of thermionic valve. This particular type does not have a negative bias on its control grid as is conventionally used in valves. Instead a tiny current is permitted to flow into the grid, and this is vastly amplified in the anode (plate) circuit. The best examples of these valves can detect currents as low as a few femtoamps (10^-15 amps). This type of valve can be ruined by handling with ungloved hands as the salts left on the glass envelope can provide an alternate path for these tiny currents.

They are of use in nuclear physics as they are able to amplify the tiny 'photo' currents created by radiation. They have, however, been supplanted by semiconductor devices in modern electrometers.

Why was this section removed? - Omegatron 16:49, August 16, 2005 (UTC)

A. Because it seemed at the time not to relate properly to the article as it was. Needs integrating properly in the section on modern electrometers as one particular way(not the only way) of making one (in addition to semiconductor types which are already included). Should have hdg : 'Valve Electrometers' or something.Light current 18:35, 16 August 2005 (UTC)

This section has now been hammered into shape and reinserted in article. See what U think. Light current 18:35, 16 August 2005 (UTC)

I know nuffink, but isn't a so-called valve electrometer just a top-quality valve voltmeter? 86.161.154.245 (talk) 16:59, 24 February 2021 (UTC)

No. But then you did answer your own question in the first three words. Seriously though, the valve electrometer is not a voltage amplifier but a current amplifier - albeit very tiny currents. 86.164.109.106 (talk) 13:52, 8 March 2021 (UTC)

Title of Diagram

I believe that this device shown is more commonly called an electroscope (not an electrometer).(at least it was when I was in school)Light current 17:56, 13 August 2005 (UTC)

I agree, so I changed it. --Heron 21:44, 13 August 2005 (UTC)

Two separate things

Im beginning to think that an eletrometer is not te same thing as a electrocope. One measures (or indicates) charge, the other measures small voltages or currenets. Am I correct?? Light current 17:27, 15 August 2005 (UTC)

How would something measure charge, though? It would report in coulombs. But coulombs where? On what? I don't understand how something could give a charge measurement except for, say, "this metal ball has an excess charge of 2 coulombs". - Omegatron 17:32, August 15, 2005 (UTC)

The electrocope indicates charge by moving its leaves. The electrometer measures something else with an electronic high impedance cct.. ( Any way I'll give you a clue about measuring charge. (Q=CV) Light current 17:46, 15 August 2005 (UTC)

As WJbeaty said above, an electroscope measures a whole bundle of things that combine to produce a Coulomb force. However, I think you have to consider the different modes of operation of the electroscope, each of which measures something different.

1. You touch the terminal with a live conductor. Electrons flow into or out of the electroscope until its potential equals that of the conductor. The net surplus or deficit of electrons on the leaves causes them to repel each other. The charge that transfers, and therefore the deflection, are functions of the original potential difference between the conductor and the uncharged electroscope.
2. You place an isolated, charged conductor in contact with the terminal. The proportion of the conductor's charge that ends up on the terminal depends on their relative capacitances. This charge remains on the electroscope when you take the conductor away. The electroscope indicates this charge.
3. You bring a charged insulator near to the terminal but don't allow any charge to transfer between them. In this case, the deflection indicates the net charge on the electrons that have been temporarily pushed towards or away from the leaves. This charge is related to the charge density on the part of the insulator near to the terminal, and the relative shapes and positions of the two. What the electroscope is measuring in this case is quite vague, because there is no sharp boundary between the electron-rich and electron-depleted regions of the electroscope.
4. You place a charged insulator on or near the terminal, ground the terminal and then withdraw the insulator. This leaves the electroscope with a net charge. The electrons redistribute themselves over the terminal and the leaves, causing the leaves to repel each other. The deflection is monotonically related to the net charge left behind on the electroscope, in a similar way to the previous case.

--Heron 19:38, 15 August 2005 (UTC)

Agree with all that Heron if you are describing an electroscope like they have in school physics labs. THe point I was making is that the common modern usage of the term electrometer is to describe an electronic instrument (hi input R/Z) that can measure small currents or voltages for use with ionisation chambers and the like. I believe firms like Kiethley Instruments used to make fine electrometers (at a fine price too). I think I used one once some years ago to measure very small voltage on a very small capacitor -- but my memory is hazy. Light current 19:56, 15 August 2005 (UTC)

Ah, that makes perfect sense. I was also thinking of an electronic meter, though, not a gold-leaf scope. I imagine they can be configured to measure the charge on an object, but I doubt anyone actually does that. Seems to me that they are used to measure something without direct contact. Would seem to be either voltage or field magnitude, though my concepts of both become hazy outside of circuits. - Omegatron 21:12, August 15, 2005 (UTC)

Reference my clue before. If you can measure very small voltages and you know the capacitance of the object , then, Hey Presto, you can calculate the what the very small charge is. Isn't electronics wonderful?Light current 22:02, 15 August 2005 (UTC)

How would you know the capacitance of an arbitrary object? You'd need a meter for that, too. - Omegatron 23:34, August 15, 2005 (UTC)

Easy ! They're called capacitance meters or bridges. Light current 23:42, 15 August 2005 (UTC)

So an electrometer doesn't measure charge. - Omegatron 00:14, August 16, 2005 (UTC)

Well I personally don't think it does; but hey I'm not an expert in this (electric) field! Maybe User:Wjbeaty may be able to illuminate us more.Light current 00:19, 16 August 2005 (UTC)

Please look here for Electometers [1] Light current 00:34, 16 August 2005 (UTC)

Yes, Lightcurrent, I was describing the gold-leaf and Braun types of electrometer electroscope. As for the discussion immediately above, Keithley do at least one electrometer [2] that claims to measure both voltage and charge. --Heron 18:53, 16 August 2005 (UTC)

Even better, Keithley have this brochure that answers the question "what is an electrometer?" and explains that they can measure voltage, charge, current and resistance. Voltage is done by "voltage balancing", a bit like an old-fashioned bridge. Charge is obtained from voltage by Q=CV, where Q is the charge on the electrode and C is the capacitance of the electrode. This can be used to measure an external charge that induces an equal but opposite charge on the electrode. The external charge might be the surface charge on an insulator over a known area, as in this NASA Mars Program experiment. N.B. It doesn't measure the charge on an arbitrary object, just the charge on its own electrode. Current-measuring electrometers use a high-gain amplifier with feedback [3]. Resistance-measuring electrometers use either a constant-current or constant-voltage method [same reference as before]. There's a wealth of information in those Keithley application notes. --Heron 19:29, 16 August 2005 (UTC)

Thanks, I will look at those app notes Light current 19:37, 16 August 2005 (UTC)

Yes , Heron, nice edit there!! :-) Light current 21:32, 16 August 2005 (UTC)

This article is looking much better. Can we cover the four modes of operation Heron listed above? - Omegatron 23:05, August 16, 2005 (UTC)

What you had in mind?? Light current 23:27, 16 August 2005 (UTC)

Quadrant electrometers

We should cover these [4]

Also, what's up with the huge list of patents? — Omegatron 15:24, 18 June 2006 (UTC)

It looks like "electrometer" has changed meaning

Classic electrometers, like the quadrant electrometer mentioned by Omegatron, are electrostatic voltmeters. You could think of them, very roughly, as refined, calibrated, variants of an electrometer.

It looks like the term has since been appropriated by the likes of Keithley for something completely different. So it may be useful to split this article up to cover the two different devices separately. Paul Koning

Well, both the old and the new refer to, essentially, voltmeters that read using just charge and not current. But you're right that there's a clear dichotomy between the purely-mechanical devices and the electro-mechanical and purely electronic devices.

Atlant 13:14, 6 September 2006 (UTC)

IMHO the electroscope text/diagrams should be removed from this article on electrometers and transfered to the electroscope article (which could use the nice diagrams and text). 99% of living people seeking info on electrometers will mean the sort of solid state electrometer sold by folks like Keithley

Tkirkman (talk) —Preceding comment was added at 15:01, 28 March 2008 (UTC)

I concur. --Chetvorno^TALK 15:08, 18 June 2008 (UTC)

Changed text formatting for section: Simple charge indicating device

This was 50% italic bold, for no reason that one can deduce from the text. Was it an extended quote? Whatever, revert if it needs to be so, but indicate why,e.g. "Quote from reference xyz". --Seejyb 13:40, 26 December 2006 (UTC)

Merge Electroscope and Electrometer?

I'm just starting this section to resolve the merger issue. The merge tag has been on a long time, and if there's no interest in merger, I'm going to remove it. --Chetvorno^TALK 10:23, 8 June 2008 (UTC)

I feel they shouldn't be merged, and I'll mention both current usage and historical usage to support this. In common usage, an electroscope is a pith ball or gold leaf type, a simple nonquantitative device to demonstrate elecrostatics in schools. An electrometer is a high impedance voltmeter (or charge meter) instrument used in laboratories, is complicated, and requires electronics knowlege to understand. The audience of readers for these two topics is quite different and should be served by separate articles. The historical usage supports this distinction. Historically an electrometer differed from an electroscope only in that it was quantitative; if it had a scale, it was an electrometer. Not much difference. However, as soon as early researchers tried to make electroscopes into quantitative instruments they rapidly got complicated: the quadrant electrometer, electrostatic balance, and piezoelectric electrometer require tech knowlege to understand. So the historical instruments fall into the same two categories as modern usage. Electroscope should cover the simple instruments up until they got scales, Electrometer should cover the relatively complicated instruments that came after. --Chetvorno^TALK 10:23, 8 June 2008 (UTC)

Removed merge tag. --Chetvorno^TALK 15:17, 18 June 2008 (UTC)

Just want to add that the gold-leaf type, among other simpler types, did receive scales eventually, and I can cite at least one textbook calling them electrometers. I'm fine with keeping the articles separate for now however.J1812 (talk) 22:43, 10 October 2013 (UTC)

Patents

I have removed the long list of patents, as they served no purpose. Moreover the list was misleading, limited to only patents issued in the US; and contained no patents earlier than 1983, whereas as this article (and electroscope) discusses, there was considerable development in the field at least 200 years prior to this. — BillC ^talk 23:22, 30 October 2008 (UTC)

I concur. I think these patent lists should be removed from articles. Anyone can easily do a patent search online. And most of the patents listed are irrelevant, having been superseded or never used. If a person that knows the field well could give a short list of the key patents that were important in the development of the field, that would be useful. But almost no one but an intellectual property lawyer has that information. --Chetvorno^TALK 00:50, 31 October 2008 (UTC)

Electroscope Experiments

This section does not belong in this article. It should be in the Electroscope article. 20.133.0.13 (talk) 15:55, 25 March 2009 (UTC)

Some Issues (which I'm about to attempt to partially fix)

1. The gold-leaf and quadrant electrometers are in a sense, also repulsion electrometers; they both work by measuring the repulsion of the same charge in one way or another.

2. My 1861 chem textbook uses the name "quadrant electrometer" to describe a considerably simpler device than Kelvin invented. This device has an index which goes between 0 and 90 degrees (hence a quadrant) while Kelvin's device, while I don't fully understand it, had a drum split into quadrants. So I conclude that this is a coincidence.

The best solution I can think of is to create a section of repulsion electrometers, and then describe the types individually in their own sections underneath, e.g. gold-leaf, Dellmann, Peltier, Bohnenberger. I will rename "quadrant electrometer" to "Kelvin's quadrant electrometer", and then put both his and the simpler one under "repulsion electrometers".

Hopefully we can make this article clearer and neater.

J1812 (talk) 22:38, 10 October 2013 (UTC)

intro way to technical and diffuse, change per

http://www3.imperial.ac.uk/pls/portallive/docs/1/7293196.PDF if you look at the pdf, on page2, the box what is an electrometer, way way way better then what you have now I don'tmyself contribute to wiki anymore for two reasons: I got tired of having to re re re correct errors (fact errors) put in by morons, and i won't do work that can be used for profit by somoene else - the idea that someone can charge for my work given freely is obscene — Preceding unsigned comment added by 50.195.10.169 (talk) 14:48, 11 April 2014 (UTC)

Neher Electrometer

I'm reading John Hersey's Hiroshima, and it mentions in chapter 3 something called a Neher electrometer, but I find no mention of this specific device here, nor can I find any fitting reference to a physicist named Neher on Wikipedia. (There's one physicist named Neher, but he's too young.) Could it be H. Victor Neher (1904-1999) Caltech professor of physics from 1931-1970? 73.158.190.173 (talk) 20:46, 8 September 2015 (UTC)

Yes, H V Neher. It was originally used for work on cosmic rays with balloon borne instruments. Millikan (also at CalTech) was involved in this work. Neher's electrometer was a particularly good quartz fibre device, although I'm not sure if there was any specific aspect to their design. The cosmic ray electrometers had a feature of a pressurised vessel enclosing them with an air pressure of a few sea level atmospheres. (It's hard to measure cosmic ionising radiation at altitude if there's nothing to ionise.) I don't know if this was Neher's innovation. Andy Dingley (talk) 22:12, 8 September 2015 (UTC)

https://books.google.co.uk/books?id=-8w8AAAAIAAJ&pg=PA120&lpg=PA120&dq=Neher+electrometer&source=bl&ots=rfjVAuplrU&sig=goSHgkIA89caWLJkbQ2U10LJrnQ&hl=en&sa=X&ved=0CDkQ6AEwBzgKahUKEwjo_fD_u-jHAhUCtxQKHWHwCBU#v=onepage&q=Neher%20electrometer&f=false may be interesting Andy Dingley (talk) 22:23, 8 September 2015 (UTC)

What voltages could they measure ?

Can we have more on what units the early electrometers were calibrated in ? Presumably related to volts since the capacitance of the electrometer will vary as the internal configuration changes ? Did/do they measure 100 V or 10,000 V ? - Rod57 (talk) 02:01, 1 December 2015 (UTC)

Since they fundamentally respond to static charges, one would assume they would be calibrated in kilovolts. I am curious as to why the scale in the illustration of the Kolbe electrometer is upside-down --Elektrik Fanne 16:38, 30 May 2016 (UTC)

Is top image really of Volta electrometers

It is labelled 'Volta electrometers' but they seem to have no scale, and are not described in the text. Unless we explain it should we just delete the image ? - Rod57 (talk) 02:14, 1 December 2015 (UTC)

The image has obviously been taken of museum or exhibition objects. It is reasonable to assume that the objects' labels describe them as such. Images are one example where original research is allowed. Since the article subject is 'Electrometer', the image would be highly relevant. --Elektrik Fanne 16:31, 30 May 2016 (UTC)

We have no idea what the museum label says, but the file name says 'electroscopes ...' which is exactly what they are, but not what this article is about.

Incomplete Sentence in “Bohnenberger electrometer” section

The second sentence in the “Bohnenberger electrometer” just trails off in mid-air, then goes on to describe a Kelvin-y Quadro-thingy-meter-doohickey that I know nothing about except that as a person who reads, I can say it might ought to be a new section there, rather than how it currently reads (no pun intended) which, to the uninitiated layperson, appears to say that the Bohnenberger electrometer was invented by Lord Kelvin, and one would think that on last names alone, that fact seems suspect. Wouldn’t it be called a Kelvin Electrometer if Kelvin invented it? I’m thinking at one point there must be the remainder of a section describing a different type of electrometer, followed by the info on the Kelvin Quadri-thingy-whatsis section. Apologies for the lack of technical-wording, I had a brain injury in 2009 and sometimes have a hard time reaching for the right words, I appreciate your patience. RobbertMacGreighgor (talk) 05:04, 1 February 2018 (UTC)

Not that Wikipedia prose is immune to stunning mid-paragraph diversions, but this particular case was due to vandalism by an anonymous IP back in October. When I see something like this I look for recent deletions - and often find vandalism. I believe I've fixed this and restored the missing section headings and text. --Wtshymanski (talk) 17:30, 1 February 2018 (UTC)

Make your mind up!

The text under the picture of the Kolbe electrometer seems to be saying that the vane is both gold ("precision form of gold-leaf instrument") and aluminium ("has a light pivoted aluminum [sic] vane"). I'll not change it since I don't know which is correct; but I will correct the spelling mistake. 86.161.154.245 (talk) 16:54, 24 February 2021 (UTC)