|WikiProject Electronics||(Rated Start-class, Mid-importance)|
|WikiProject Technology||(Rated C-class)|
need to discuss the concept of balance
The concept of a balanced bridge is central to many practical uses of bridges. Someone needs to explain this. Is this a good place? As a measurement tool, we adjust the bridge to balance, or null, to establish the unknown value by comparison with the known arm. However the balance concept is fundamental to many applications of bridges that are not measurement related, and is a key idea used by circuit designers. It allows the currents flowing across the horizontal paths to be independent of the voltage imposed on the vertical paths.
In my experience use of an unbalanced Wheatstone bridge is as common as use of a balanced one. For example, in some strain gauge measurements both R3 and Rx (and sometimes R1 and R2 as well) are unknown, being the strain gauges themselves. Instead of trying to determine these resistances, the objective is to measure the potential difference, which is proportional to the strain. The article doesn't really cover this class or applications.
Concerning the circuit diagram of Wheastone bridge, it would be nice to add the orientation of currents and voltages in the branches. It is easy to find out which conventions/orientations have been taken with the equations displayed below but it would be easier to make it to appear explicitely on the diagram. I didn't add any modification as I dont know how to do it :). That was just a remark to help improving the article.
Can't we tell how it was used? This is in the bowels of the technology and does a great disservice to the fact that it was the first piece of network management gear. - carl ford firstname.lastname@example.org —Preceding unsigned comment added by 220.127.116.11 (talk) 11:06, 28 October 2008 (UTC)
Wheatstone did NOT invent the Wheatstone bridge (see any full biography of him).
- Updated with the correct inventor -- DrBob 18:54 30 May 2003 (UTC)
Should we add the balance conditions for the wheatstone bridge? mickpc
- It seem that the formula to calculate the Equivalent Resistance RE has a little error
(R1*R2)(R3*R4) should be replaced by (R1+R2)(R3+R4). Please verify my suggestion. Tks.
what about the emeter in referance to scientologys use of this type device?
I kindly request a brief discussion of how AC measurements are made with a Wheatstone... and/or how to measure inductance and capacitance (or a link to said information). If anyone is familiar with that, thanks in advance. Catapultsam 11:15, 15 April 2007 (UTC)
The maths seem to start of with R1, R2, R3 and Rx, which are defined. Later on R4 appears without explanation
- R4 should be changed into Rx since the picture above is taking Rx as an unknown resistor --besterer
In the article, they say that the first set of equations are for B and D. I believe the author meant B and C as current I1 does not feed into D.—The preceding unsigned comment was added by ZaydHammoudeh (talk • contribs) 22:09, May 31, 2006 (UTC).
Current article is wrong. Someone changed the image without checking definitions in the article.Orz.(Sorry, I don't have enough time to correct it now.)—The preceding unsigned comment was added by 18.104.22.168 (talk • contribs) 04:11, June 7, 2006 (UTC).
- I restored the original diagram and adjusted some of the changes that had been made since it was replaced on May 22. The newer diagram, while perhaps nicer-looking, uses different numbering of the resistors and junctions. This change in numbering left the mathematical derivation incorrect. Several editors had made changes to individual sentences where they noted a discrepancy with the diagram, but this was not sufficient to fix the problem. I have reverted those changes, so the article should now be in accord with the diagram.
- If the consensus is that the other diagram is better, someone needs to go over the article carefully and rework the derivation so that it is in accord with the new diagram. Alternatively, someone could relabel the new diagram so it matches the old one's numbering.--Srleffler 17:18, 23 August 2006 (UTC)
Text / Diagram Agreement
Please verify that my suggestion is a correct one. In order to have the text agree with the diagram, I feel that the following sentence, which constitutes the fourth paragraph:
"If the bridge is balanced, which means that the current through the galvanometer Rg is equal to zero, the equivalent resistance of the circuit between the source voltage terminals is:"
should be changed in this way:
"through the galvanometer Vg is equal to zero,"
since the label "Vg" appears on the diagram and the label "Rg" appears nowhere on the diagram.
- The whole sentence is irrelevant; we're not interested in the resistance presented to the source. I shall delete it.
- Incidentally, I notice that in the diagram R2 is no longer shown as adjustable. Is this a mistake? --catslash (talk) 22:56, 9 January 2008 (UTC)
- In my contribution of the German article for the Thomson Bridge you may find a picture, which you may use.
- But I am not shure what you want, if you would try to explain it in more detail, you might get more response.
Rainglasz 18:44, 3 September 2008 (UTC)
- I couldn't get the link to work from the de.wiki site so I added a link from the Scientology section. If someone thinks it isn't PC, feel free to find a better pic. Canoe1967 (talk) 19:44, 29 December 2011 (UTC)
It's a good start, but needs more :) For instance, the circuit on the page is specifically a quarter-bridge set up. A good site to refer to for more info is  though the focus there is more on strain gauges. Try  too. Happy editing :) —Preceding unsigned comment added by Cirmae (talk • contribs) 23:53, 11 May 2009 (UTC)
Equation for Rg
Replacing V_g with R5 and Rx with R4, and solving in terms of conductance (G1=1/R1, etc) I came up with this:
(G1*G4-G2*G3) V5 = Gs * ------------- (G1+G2)(G3+G4) + G5(G1+G2+G3+G4)
This seems right, but then I work a problem like this once every five years or so. The sign of V5 is a matter of convention. My diagram was D-B but I think the equations in this article use B-D. I would have liked to find this in the article rather than work it myself, but then this is no longer a balanced bridge so perhaps it doesn't belong. — MaxEnt 11:30, 8 July 2013 (UTC)