Amazing 19th Century Tech - The Galvanometer

In this video I show off one of my prized artifacts - a mid-20th century reproduction of the first piece of bench gear made - the Mirror Galvanometer! This was the must-have kit for the mid-19th century laboratory, and having a way of measuring minute currents at a time before signal amplification meant that every micro-amp saved was precious. Enjoy!
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[@theCodyReeder]

That’s so cool! Thanks for sharing!

[@doggodoggo3000]

Dude. Fran is the freaking best. What an incredible lady. Have you seen her line of boutique guitar pedals? (your channel is great btw, long time fan. cool to see you over here)

[@jondhuse1549]

It is incredibly nice to see you in action again... yay!

[@AlanCanon2222]

Seconded!

[@Skraboing649]

@@AlanCanon2222 Thirded! 👍☺️

[@AlanCanon2222]

Love me some mirror galvanometer! You go, William Thomson! Get that Wildman Whitehouse! Near as I know, these weren't used aboard ship. They were for the receiving station, to read the very very smeared out pulses coming in off the first (1858) cable, which in turn are caused by ions in the seawater being dragged back and forth by the current inside the cable. Wildman Whitehouse's idea was to put 2,000 volts on the cable, which immediately blew a hole in the insulation and ruined the undersea cable, around September 1, 1858. While the next cable was being laid, Thomson developed the mirror galvanometer. Happily, the next successful cable laying trip not only replaced the cable, but they were able (through what amounts to a 1,500 mile long Wheatstone Bridge) to identify the locale of the break in the first cable: they grappled it, repaired the bad section aboard ship and laid it back into the ocean, so now (late July, 1866) they had two cables! Transmission rate was around 0.5 baud. The debacle caused Whitehouse to lose his job, replaced by Thomson, and the entire enterprise earned Thomson his baronetcy. I also think, FWIW, the "Period" marked on the maker's tag is the natural period of the spring: if you count out seconds while the calibration takes place, it's very nearly 4 seconds per swing.

[@generatorjohn4537]

Alan, Very nice summary on the transatlantic cable. Thanks I used a wheatstone or kelvin bridge years ago to measure RTDs (resistance temperature detectors) for their accuracy. They were usually the 10 ohms at 25 degrees C type. Oh and they were copper. Frans topic today cleared some cobwebs. Never thought I would ever be thinking about this kind of technology after all these years.

[@AlanCanon2222]

@Christie Malry Haha true, but it must have seemed like a science fiction dream come true back in the 1860s!

[@effexon]

@@AlanCanon2222 so they also had difficult decision to make, either to send morse code telegram, small message, quite pricey over the line or send long letter slowly over normal mail but maybe cheaper and with more details.

[@AlanCanon2222]

@@effexon One hop latency with sails + primitive steam was about 14 days. I get it.

[@effexon]

@@AlanCanon2222 haha, Im not sure I understood anything what you said. I tried to make analog from corona times that people still need face-to-face time for complex discussions, simpler messages can be sent via IM and novellists can describe complex but not timely critical things in elaborate way in book, somehow how people who liked writing letters in that period could be very talented in their description of things and emotions. Humans still "tick" at same speed as those times despite insane advancement in ICT, communication tech.

[@mfbfreak]

12:00 that's not wood - it's a phenolic resin-like material reinforced with woven fibre. A bit like bakelite but with a different filler.

[@robcameron8453]

trade name in the UK is "Tufnol" very useful material

[@DanielleWhite]

I was thinking the same thing; I used to have weaving shuttles made of phenolic and the texture looked the same.

[@theshannonlimit1114]

it is sometimes also called novotext

[@dogwalker666]

Looks like Paxolin.

[@stephenbell9257]

@@dogwalker666 Paxolin is resin bonded paper but this material is resin bonded fabric. It is much tougher than Paxolin and considerably more expensive

[@TheDigitalAura]

Thumbs up just for the intro, so nice to hear it again.

[@simontay4851]

That galvanometer is more sensitive than most modern multimetres. Pretty amazing precision even now.

[@LeifNelandDk]

It's no problem to create such sensitive instruments today. However, there is almost no use for it. If you try to measure the voltage after a switch, you might measure almost full voltage because of the tiny leakage currents.

[@sirtoby2727]

Good to see you back, Fran! This Video brings back long forgotten memories! In my last year in grammar school back in 1992 I did my final assignment measuring small charges with the school's mirror galvanometer that was built into the physics classroom's wall. I had to come up with a calibration procedure to show that the meter can actually be used to measure electric charges, as long as these are discharge through the meter rather quickly. They gave me an AD-converter connected to a PC with next to no documentation. Was great fun in the end and this eventually led me to becomming an electrical engineer :)

[@BruceNitroxpro]

TobyAumueller , You must cringe at Fran's lack of familiarity with some of the gear, despite her great knowledge base.

[@InssiAjaton]

There is a version optimized to measuring the integral of a current. It is called Ballistic Galvanometer. The idea is that its light beam deflections are highly damped and you can read the FIRST peak deflection. We had a lab exercise related to measuring a hysteresis loop. Sort of complicated math was involved, as is evident in our text book "Electrical Measurements" by Forest K. Harris, Physicist at National Bureau of Standards. Library of Congress number 51-13122. That book covers all the gruesome details in 40-some pages.

[@popcorn00109]

Looking great Fran! I hope you’re feeling better too!

[@WCM1945]

In 1968, I took a job as as an "Electronics LAb Technician" at UAB (University of ALabama at Birmingham) Sloan-Ketteriing Resarch institute. It consisted primarily of setting up and operating the JEOLCO (Japan Electron-Optical Company) nuclear magnetic resonance spectrometer, which used an electromagnet for its field. The curent for that magnets was regulated by a feedback loop consisting of a small coil placed in the feild of the magnet. Any slight variation of the field strength would induce a small current in that coil, with was coupled to the rotor of a mirror galvanometer similar to what you are showing. The spot would fall on one of two photocells which in turn controlled the current through the field magnet's coil. This circuit was called the "super stabilizer". The galvanometer movement was sealed in a a small vacuum chamber to eliminate thermally-induced drafts.

[@zoran9a3hpdiy49]

When I was young I just read that this instrument was in use. But never saw in live. Thanks Fran.

[@ElektronikLabor]

I love how mechanically complicated the first instruments were and I totally enjoy to watch how they work

[@rickevans3959]

The movement is a gold ribbon real gold!

[@GraemePayne1967Marine]

First, welcome back! Aaah, the memories. For about 15 years I worked in the electronic calibration lab of a US Naval Shipyard. (It closed in 1996.) The lab had a mirror galvanometer very much like the one you have there. I don't remember the manufacturer, but I do seem to recall that it was made before WW-II. Maybe 10 years before i was born. The galvanometer was not used very much, but there were a few calibration procedures that required it. If I ever manage to unearth my notes from back then (I have moved three times since then) I may be able to remember more about it. Thanks for showing it. Finally, more memories generate by the TI-30! I don't think I has one of those, but I did have a later programmable model. That one used magnetic cards to store programs. It had an available thermal printer it could dock into for printing programs and results.

[@mikefochtman7164]

Hey shipmate! I worked in R-3 meter cal, New London for a bit. I remember using a similar galvanometer to measure cable resistances of some really heavy-duty cables used on submarine batteries. Had to make sure the 'lugs' were attached adequately and acceptance criteria was way down about a milliohm or something like that. We normally used a more modern 'calibrator' for most of the benchboard meters on board the 'boats'.

[@GraemePayne1967Marine]

@@mikefochtman7164 Hello there! I was at Charleston Naval Shipyard. Started as an apprentice in the electronic cal lab, & eventually moved up to the electrical-electronic standards lab. I was the last one to close & lock he doors of those labs - a sad day. There was at least a million dollars worth of standards & test equipment, & last I heard it's still all there.

[@theshannonlimit1114]

4 seconds is the average amount of time it should take to move end to end full scale. and when you are zeroing it, try shorting the coil through a resistor about 1/10 times the resistance of the coil, the galvanometer will then be critically damped and wont oscillate.

[@AlanCanon2222]

Genius application of Biot-Savart and Lenz!

[@fepatton]

Really cool! This falls squarely Into the "People were GENIUSES with electro-mechanical devices!" category. Had a thought about the "Period 4 seconds" - I wonder if it's the oscillation period of the mirror"? I'm not sure why that would be important, but when you were calibrating it, I noticed the period seemed to be in about that range. PS: I miss my TI-55!

[@TentoesMe]

You could see the 4 second period while she was adjusting the lever.

[@reset3065]

Someone asked what would you do with it? It has been more than a day or two since I worked with that piece of equipment but just an FYI. The uses are many but one I have seen that is probably lost knowledge today was and oxygen meter. They had the same type movement built in a sample chamber. The mirror was mounted on a barbell shaped piece of glass work. The barbell was filled with nitrogen. It had a strong magnet surrounding it and was mounted on the taught band. We would fill the test chamber with nitrogen and zero the meter. When oxygen was passed through the chamber the magnetic effect on it would cause it to concentrate around the barbell and deflect it. Basically the nitrogen was nonmagnetic and the oxygen was magnetic. The movement being sensitive enough to measure the difference between the magnetic forces working on the gases was an amazement. We had to regulate the pressure in the chamber. The movement would respond to pressure variations. Thank you for posting.

[@gevmage]

I haven't even watched this and I'm excited. A galvanometer! The heart of all analog gauges! Whoo-hoo!

[@jdhtyler]

SOHCAHTOA that takes me back to 1975, funny thing was a lad in the class said "I know the word but I don't know how to spell it" Our maths books in the UK were full of garage problems and Spike the spider and Fred the fly. Later in engineering I would use it 4 ball bearings, a height gauge, a micrometer to calculate the internal diameter of a machined undercut part, this method negates a LOBED diameter problem.

[@jamesgoacher1606]

Oh lady that was wonderful. That instrument would not have been Vintage when I started my Apprenticeship in 1961. The torque of the current acts against the torsion of that suspense wire you showed. It's Len'es Law that you referred to which of course you know. Him and Faraday had/have it wrapped up. Maxwell is advanced. I was trying to figure out the sensitivity in Ohms/Volt while you were giving the figures. I know the Avo-8 of the time was 20k/V but I did not trust myself to try and work this one out. Wonderful, thankyou.

[@jonelectronics510]

Great to see you again Fran! Always something fascinating to show.

[@Dukers2300]

Yay you're back! Great to see you, cool piece of vintage kit!

[@gbradley]

Yay! So happy you're back and feeling energetic Fran

[@steveroberts1861]

Great to see you back

[@airmann90]

Good to see you back. Another fascinating video!

[@PrismaxMan]

Fran, You are awesome for sharing this!

[@goodun2974]

The drawing of the light-beams' path reminds me of a transmission-line speaker cabinet; the purpose of the multifaceted beam path being to make the device operate as if the cabinet is larger than it actually is, which is indeed the function of a transmission line speaker.

[@isoguy.]

Great to see you on the tube again. Really enjoy the retro tech episodes. Thanks for sharing

[@Syntox]

Great to see you again - you look and sound refreshed!

[@BartHull]

Thank you. Love the galvanometer testing and how sensitive it is. I didn't understand the reason for the mirrors until you explained their use in increasing the width of the full range. Even followed the math to see how it worked.... Awesome!

[@BRUXXUS]

Original intro! 🥰 Love it so much. Happy to have you back, Fran.

[@PaulinesPastimes]

Welcome back Fran. Glad you are feeling refreshed.

[@christopherkise]

Excellent, a real happy strangely fascinating video. Thank you

[@jamesmihalcik1310]

Wonderful video. That is a lens on the pivot wire. A Galvanometer is still employed today within the blasting industry, measuring continuity without prematurely setting off the charge. Jim M.

[@chrisj2848]

Its amazing to see such ingenious forgotten equipment. I didnt know this existed, thanks Fran for sharing. Love this video.

[@neclimdul]

It's great to see a happy Fran. Glad to see you doing better! Fun video too.

[@sewskates]

Great video Fran. Thanks.

[@vatovega]

It's truly a pleasure to see your new videos again! I battle many illnesses and your videos make me excited to tinker with electronics:)

[@masteryoda394]

Interesting piece of old tech that I have never seen before, thank you.

[@lexologics]

good to have you back, I'm fine in Amsterdam thanks!

[@danielpereira2623]

Hi Fran, sensational you always bringing news.

[@bucyruserie1211]

Great video Fran!!!!

[@FraterAlex]

Very interesting device! Thanks Fran!

[@nilo70]

Thank you Fran

[@melody3741]

I'm doing wonderful Fran thank you! This is really cool.

[@jellomusic]

Love your videos Fran.

[@alexfunke214]

Fran, I love your show, and the cool, eclectic things you show us!

[@Miata822]

Fascinating device. Thanks for sharing.

[@blckcloud15253]

Good to see you up and running again friend and thanks for the advice about etching boards I was able to acquire some transfer film and I'm going to get into eagle and hopefully do my first legitimate headboard and several years so once again thanks for being here

[@davidmartin5810]

thanks Fran great explanation

[@T2D.SteveArcs]

A thing of beauty is a joy forever 😎👍👍 thank you Fran

[@jhonwask]

I like all your videos, especially the shorter ones. Thank you.

[@frankowalker4662]

Yeah, Fran's back in the lab. Great vid.

[@johnmoor8839]

good to see you looking so well

[@JohnSmith-gm4fj]

Commonly used as a continuity tester for blasting. Even today model rocket enthusiasts use them to make sure there aren't any breaks in the line prior to launching. The amount of current they put in insufficient to set off a blasting cap or set off an igniter but it's enough to test continuity. Very useful device.

[@mick7909]

Ohh Frans collection, great xxx

[@anthonybarra2391]

Clever stuff, nice break down of that engineering marvel of its time.

[@ve3krp]

Interesting device.... nice to see you again....

[@1HayesEng]

Very good ! Thanks.

[@cgoad]

Hi Fran! I'm glad to see you back and in good spirits. I love old (antique) instruments of just about all kinds, but I can't collect them (too $$) so I really enjoyed both looking at this one and your explanation. Good stuff!

[@renaldojones1054]

Love you Fran. Love your channel...from Jamaica

[@SimonSozzi7258]

You look refreshed 🙏💗🥰

[@aaronm9478]

Welcome back, Fran! :D These old tech videos are so cool! Crazy to see how crazy the engineering had to be for these devices. Looks absolutely primitive by today's standards. Super neat!

[@jonrambin1572]

I saw the teaser photo you posted a few days ago. I'd have never guessed what you were going to present here today. Great fun. Thanks!

[@harmlesscreationsofthegree1248]

Hi Fran, so good to see you 😸

[@tomgeorge3726]

Great video Fran, nice Taught Band Movement demo.👍👍👍👍

[@Digital-Dan]

Glad you are thriving.

[@meettechniek]

I think something went wrong with the measurement. The instrument label says the sensitivity is 0.0005 uA/mm. The scale is approximately 100 mm long, so the full scale current should be 0.05 uA (50 nA). The full scale current that you have calculated of 5.5 uA is 100 times bigger. Depending on your measurement circuit maybe you must take the input resistance into account. And a little hint: you can use a normal multimeter in the volt-range as a very sensitive current meter. A voltage of 1 volt ascross the input resistance of 10 Mohm corresponds with a current of 100 nA. I use this methode to measure diode leakage currents.

[@carolmartin7042]

Galen Martin, Thank you. I enjoy the older laboratory equipment.

[@thankyouforyourcompliance7386]

Love to see more stuff from the attic. Some amazing technical devices back from the 19th or 20th century before everything has become a computer.

[@johnpossum556]

Nice share. That beam path reminds me of an SLR camera's. I've been in several specialty museums and never yet seen one of these until today.

[@gregfeneis609]

Hey, Fran, glad to see you seem in a little better shape than in recent videos.

[@radiorob7543]

That's a beautiful piece. I just subscribed. I don't know why I havent sooner. You have a great way of explaning things. I should know. I have worked in the technical customer service field for years.

[@danlogicaluk8721]

Thanks fran

[@bjorndimming6304]

Love your videos!

[@MarcelHuguenin]

Nice to see you back Fran! Hope you feel ok.

[@parsifal40002]

Welcome back! Good to see you again! Miss your beautiful eyes as well as your technical skills!

[@tomhobbies6888]

its good to see you looking all fresh and bright your kinda glowing and you sound better good to see you sharp again.. love the vids later

[@jerryg50]

I have watched some of your videos... Very interesting and extremely impressive! :-)

[@jeanpierre3193]

Great instrument!,CDRX is Critical Damping shunt Resistor (X value is determined for adjust the total parallel resistance across the the moving coil and CDRX) This résistance is extremely accurate! Regards to France!

[@nathanokun8801]

Using mirrors and multi-path to multiply the motion of the sensor (mirror+magnet needle on the thread) to a large-enough value to be used to reliably measure values as a test equipment device. A "steampunk" electronics classic!

[@IckyStickyG00]

Love your vids!

[@Tocsin-Bang]

Thanks Fran. That took me back I used to repair school science equipment. In the UK this kind of thing was common for many years, although our instruments were commonly made by Pye, Gallenkamp, Griffin & George and one or two others. The instruments I hated were ribbon suspension galvanometers.

[@jimc9823]

Very cool!

[@ricardosales864]

Yes! I liked your video, very interesting! hugs

[@keithking1985]

You always have the coolest things : )

[@arthurdanielles4784]

Got one of these in my collection. Originally a university lab teaching aid sold off in the 1980s along with a box of various mA mV et meters plus two DC and two AC meters up to 20,000 volts (quite bulky but fully calibrated and verified with documentation et ) in solid leather cases. 👀👍

[@alimaleki217]

Thanks for sharing Fran! Imagine what they would have given for a Fluke 87 back in the day!

[@scottthomas6202]

I think a lot of people have made the coil and compass galvanometer as a child... Cool gizmo..and it's great that you're preserving it , as well as letting us all see it in this video .

[@Jjosh1358]

This was really fascinating. Awesome video. I think it's really cool how such a sensitive and delicate piece of test gear has lasted this long. And the trigonometry stuff. I haven't had to think about that since my junior year of high school and it was quite refreshing.

[@crusinscamp]

Interesting video. The instrument is vaguely reminiscent of an electrostatic kilovoltmeter. We had them all around the plant when I started working there in 1981. There's a lot less now. The electrostatic kilovoltmeter is also an electromechanical instrument, it uses electrostatic attraction (via plates and delicate needle movement mechanism) to deflect the needle. They have some interesting properties. They work on AC or DC. On AC they impose a fairly pure but small capacitive load. On DC the impedance is virtually infinite (i.e. it's as good as your insulators are). Anyway, neat video. The stories of the first trans-Atlantic cables always fascinated me an this is an important part of the picture. I like how they use light itself as a zero weight/mass meter movement. We watch this by shooting light through glass fibers. It's both fascinating and amazing.

[@Indiskret1]

My physics teacher in high school had one of those and it made an impression as I still remember it some 40 years later. I had many great teachers, probably saved my life (but that's another story).

[@stevendunn264]

Fran, you look great.

[@realcygnus]

Neat-O ! I could swear I seen this before.

[@theoriginalbabycub]

I used one of these in a slightly more modern version in the early 80s in school physics. It was at the centre of a Wheatstone Bridge in configuration to measure an unknown resistance.

[@lordmuntague]

Wow! This is classic FranLab, an absolutely superb video. Good to see you back Fran, you look and sound as bright as ever. BTW: scale from 0 to 10? I guess cranking it up to 11 came later... #o))

[@stevejohnson1685]

Hi, Fran - It's great to see you back. I think the period (4 seconds?) refers to the settling time of the mechanism. It acts as a damped oscillator. At about 6:30, you can count out four seconds as the illumination wobbles. When it's tuned correctly, the oscillation is "critically damped" as opposed to "underdamped" or "overdamped." See more here: hyperphysics.phy-astr.gsu.edu/hbase/oscda.html

[@larrykent196]

Thanks.

[@paulbennell3313]

Yeah, I reckon trying to use one of these on a ship must've been...character building... We had to start somewhere of course and in principle, all subsequent developments of the moving iron/moving iron meter owe their M.O. to items such as this. Fascinating stuff.

[@chanvalentine8283]

Huzzah, I always wondered what one of these looked like in perspective to everything around it.