Milestone-Proposal:Anderson Bridge

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Docket #:2023-05

This proposal has been submitted for review.

To the proposer’s knowledge, is this achievement subject to litigation? No

Is the achievement you are proposing more than 25 years old? Yes

Is the achievement you are proposing within IEEE’s designated fields as defined by IEEE Bylaw I-104.11, namely: Engineering, Computer Sciences and Information Technology, Physical Sciences, Biological and Medical Sciences, Mathematics, Technical Communications, Education, Management, and Law and Policy. Yes

Did the achievement provide a meaningful benefit for humanity? Yes

Was it of at least regional importance? Yes

Has an IEEE Organizational Unit agreed to pay for the milestone plaque(s)? Yes

Has an IEEE Organizational Unit agreed to arrange the dedication ceremony? Yes

Has the IEEE Section in which the milestone is located agreed to take responsibility for the plaque after it is dedicated? Yes

Has the owner of the site agreed to have it designated as an IEEE Milestone? Yes

Year or range of years in which the achievement occurred:


Title of the proposed milestone:

Anderson Bridge 1891

Plaque citation summarizing the achievement and its significance:

The Anderson Bridge measures inductance in an ac bridge. The unknown inductance is compared with a standard fixed capacitance, which is connected between two arms of the bridge. It works in a similarly to the Wheatstone Bridge, used to measure resistance. Anderson's method is capable of precise measurements of inductance over a wide range of values from a few micro-Henrys to several Henrys

200-250 word abstract describing the significance of the technical achievement being proposed, the person(s) involved, historical context, humanitarian and social impact, as well as any possible controversies the advocate might need to review.

IEEE technical societies and technical councils within whose fields of interest the Milestone proposal resides.

In what IEEE section(s) does it reside?

United Kingdom and Ireland (UKRI) Section

IEEE Organizational Unit(s) which have agreed to sponsor the Milestone:

IEEE Organizational Unit(s) paying for milestone plaque(s):

Unit: IEEE Power electronics Society (PELS)
Senior Officer Name: Brad Lehman President

IEEE Organizational Unit(s) arranging the dedication ceremony:

Unit: IEEE Power Electronics UKRI Section
Senior Officer Name: Bing Ji

IEEE section(s) monitoring the plaque(s):

IEEE Section: UKRI Section
IEEE Section Chair name: Izzet Kale

Milestone proposer(s):

Proposer name: William Gerard Hurley
Proposer email: Proposer's email masked to public

Please note: your email address and contact information will be masked on the website for privacy reasons. Only IEEE History Center Staff will be able to view the email address.

Street address(es) and GPS coordinates in decimal form of the intended milestone plaque site(s):

University of Galway, University Road H91 TK33. 53.2792N, 9.0617W

Describe briefly the intended site(s) of the milestone plaque(s). The intended site(s) must have a direct connection with the achievement (e.g. where developed, invented, tested, demonstrated, installed, or operated, etc.). A museum where a device or example of the technology is displayed, or the university where the inventor studied, are not, in themselves, sufficient connection for a milestone plaque.

Please give the address(es) of the plaque site(s) (GPS coordinates if you have them). Also please give the details of the mounting, i.e. on the outside of the building, in the ground floor entrance hall, on a plinth on the grounds, etc. If visitors to the plaque site will need to go through security, or make an appointment, please give the contact information visitors will need. The former Physics Laboratory in the Quadrangle of the University of Galway

Are the original buildings extant?


Details of the plaque mounting:

In the Archway of the Quadrangle, near the Physics Laboratory, next to the Reception fully accessible to the public

How is the site protected/secured, and in what ways is it accessible to the public?

Fully visible and accessible to the public

Who is the present owner of the site(s)?

The University of Galway, formerly Queen's College

What is the historical significance of the work (its technological, scientific, or social importance)? If personal names are included in citation, include justification here. (see section 6 of Milestone Guidelines)

In the mid 19th century, as the field of electrical engineering was evolving, there was great interest in the measurement of electrical components viz. resistance, inductance and capacitance. Michael Faraday and Joseph Henry independently discovered inductance in 1831/32. James Clerk Maxwell introduced a ballistic deflection method for measuring inductance in 1865. This was a variation on the Wheatstone Bridge (1843) for measuring resistance. The Maxwell Bridge balanced the L/R time constant against a known RC time constant. Several modifications followed and the most famous one was the Anderson Bridge (1891) named after Alexander Anderson, Professor of Natural History at the Queen’s College, Galway, now known as the University of Galway [1]. The Anderson Bridge became the de facto bridge for measuring inductance, described in the Bulletin on the Bureau of Standards by E.B. Rosa and F.W. Grover, the leading exponents of all things inductance at the time [2]. The Anderson Bridge is still described in text books for Electrical Engineering [3]. It is also described in “A History of Impedance Measurements” [4]

What obstacles (technical, political, geographic) needed to be overcome?

The Maxwell Bridge, was based on the deflection of a ballistic galvanometer, which was difficult to calibrate due to its dependance on a moving coil to detect small movements near the balance points. The Anderson Bridge removed this obstacle by balancing the L/R time constant on an unknown inductor with the known RC time constant of a capacitor. Capacitors were more stable and easier to measure.

What features set this work apart from similar achievements?

The Anderson Bridge remained the standard bridge for measuring inductance until the advent of digital methods in the 1970’s. Most undergraduate textbooks up until that time referenced the Anderson Bridge for the measurement of inductance. It formed the trio of bridges, Wheatstone, Anderson and Schering Bridges for measuring resistance, inductance and capacitance respectively.

Supporting texts and citations to establish the dates, location, and importance of the achievement: Minimum of five (5), but as many as needed to support the milestone, such as patents, contemporary newspaper articles, journal articles, or chapters in scholarly books. 'Scholarly' is defined as peer-reviewed, with references, and published. You must supply the texts or excerpts themselves, not just the references. At least one of the references must be from a scholarly book or journal article. All supporting materials must be in English, or accompanied by an English translation.

[1] On Coefficients of Induction, A. Anderson, Philosophical Magazine, vol. 31, pages 329-337
[2] Measurement of Inductance by Anderson’s Method, E.B. Rosa and F.W. Grover, Bulletin of the Bureau of Standards, vol. 1, no. 3, pages 291-293
[3] Optimization of the Anderson-Bridge Experiment, P.Arun, K. Kumar and Mamta, Resonance (Springer), Ch 15, pages 244-256, 2010
[4] A History of Impedance Measurements, H.P. Hall, General Radio Company, page 8, 1992
[5] Irish Innovators in Science and Technology, C. Mollan, W. Davis, B. Finucane, Royal Irish Academy, , page 184-185, 2002
[6] Anderson’s Bridge, Wikipedia
[7] Alexander Anderson (physicist), Wikipedia

Supporting materials (supported formats: GIF, JPEG, PNG, PDF, DOC): All supporting materials must be in English, or if not in English, accompanied by an English translation. You must supply the texts or excerpts themselves, not just the references. For documents that are copyright-encumbered, or which you do not have rights to post, email the documents themselves to Please see the Milestone Program Guidelines for more information.

Please email a jpeg or PDF a letter in English, or with English translation, from the site owner(s) giving permission to place IEEE milestone plaque on the property, and a letter (or forwarded email) from the appropriate Section Chair supporting the Milestone application to with the subject line "Attention: Milestone Administrator." Note that there are multiple texts of the letter depending on whether an IEEE organizational unit other than the section will be paying for the plaque(s).

Please recommend reviewers by emailing their names and email addresses to Please include the docket number and brief title of your proposal in the subject line of all emails.