Amazing 19th Century Tech - The Galvanometer

[@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! 👍☺️

[@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.

[@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.

[@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.

[@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.

[@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.

[@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.

[@ElektronikLabor]

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

[@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.

[@9a3hp]

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

[@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.

[@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!

[@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.

[@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.

[@gevmage]

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

[@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.

[@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.

[@Syntox]

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

[@alexfunke214]

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

[@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.

[@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!

[@isoguy.]

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

[@steveroberts1861]

Great to see you back

[@erik365365365]

Love this comment section! No negatives! Happy to see you back in the lab looking at wonderful beautiful tech. Now here’s a negative, Fran stop being so awesome it makes me fee less superior!

[@gbradley]

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

[@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 .

[@rickevans3959]

The movement is a gold ribbon real gold!

[@gregfeneis609]

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

[@PaulinesPastimes]

Welcome back Fran. Glad you are feeling refreshed.

[@gordselectronicshobby3853]

The Galvanometer was also used to check wiring to blasting caps for dynamite and other explosives. I use them when setting up charges while in Vietnam.

[@jonelectronics510]

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

[@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.

[@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!

[@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.

[@parsifal40002]

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

[@johnmoor8839]

good to see you looking so well

[@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. 👀👍

[@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:)

[@BRUXXUS]

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

[@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.

[@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!

[@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!

[@carolmartin7042]

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

[@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).

[@neclimdul]

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

[@ElectronicTonic156]

CDRX is the critical damping resistance. Put 68000 ohm in parallel with the coil, and mechanical oscillation will be critically damped such that the mirror/spot will stabilize at its final destination as quickly as possible without any overshoot.

[@lexologics]

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

[@anthonybarra2391]

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

[@Digital-Dan]

Glad you are thriving.

[@Simonjose7258]

You look refreshed 🙏💗🥰

[@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.

[@MarcelHuguenin]

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

[@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!

[@chrisj2848]

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

[@charlesvanberg9259]

Fran. Try using a short on the input to slow the swinging.

[@Abolish_The_S-N-T_NOW]

Ohh Frans collection, great xxx

[@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

[@arposkraft3616]

@6:50 it would be in a cardanic axle setup similar to compasses , though even with that id figure it would be hard

[@claytonbonser7629]

With respect to the instrument's sensitivity, look again at the card, it says 0.0005uA per millimetre at 4:15. Assuming a small division is 1mm, FSD= 0.05uA

[@nilo70]

Thank you Fran

[@airmann90]

Good to see you back. Another fascinating video!

[@T2D.SteveArcs]

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

[@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.

[@foxabilo]

If I recall correctly the ship mounted ones had the coil in light machine oil to dampen out the movement.

[@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

[@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.

[@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!

[@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.

[@masteryoda394]

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

[@gordonlawrence1448]

This is one of my areas of expertise as I studied physics not electronics. Mirror galvanometers are usually called "light spot galvanometers" in the UK and were still in use in schools at least to the 1980's. I know as I used one for my A level physics experiments. There are actually two types. The magnet/coil type is the most sensitive but also most expensive to calibrate and fix. The other type used a bi metallic wire arrangement terminated at one end that moves a mirror and the minute amount of heat causes mirror deflection. Less sensitive but way easier to fix. I think the two metals were an alloy called constantan and iron. I gave up in the end and used my "Tandy" multimeter as the current went all the way down to 25uA FSD. I'm now designing electrometers measuring femto amps. Now that's a fiddly job as just touching the components will take them way out of calibration and you have to use them cold to avoid leakage. Currently trying to use dry ice.

[@PrismaxMan]

Fran, You are awesome for sharing this!

[@renaldojones1054]

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

[@alimaleki217]

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

[@tedhaubrich]

Any adult that can remember basic trig is pretty impressive in my book. I think I knew how to do that for about 3 days in high school, and then promptly forgot all of it about an hour before the test. Pretty cool piece of kit. I find it interesting that the original with cloth wound wire and probably a ceramic light socket could possibly have held up a bit better than the 1950 reproduction. Though I guess you do see lots of antique mirrors where the silvering has degraded.

[@hugeshows]

You might try shorting or shunting the coil when zeroing it, the needle motion should be damped somewhat.

[@harmlesscreationsofthegree1248]

Hi Fran, so good to see you 😸

[@jhonwask]

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

[@DaLincer]

Fran, did you consider the 68,000 input resistance of the device? The current through the device depends on this as well as the external resistance. Second item, looking at the galvanometer block, do I see a lens in front of the suspension wire, and a mirror behind?

[@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

[@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.

[@stevendunn264]

Fran, you look great.

[@FraterAlex]

Very interesting device! Thanks Fran!

[@dashcamandy2242]

I love the super-close-ups of the TI-30. By far my favorite calculator ever, I used mine in high school when everyone else was using TI-31 SOLARs and TI-81/82s. So what if it was a hand-me-down from my father, so what if I actually had a TI-82 and a TI-30X (and some Casio as well) at the time? NOBODY had the gold tone and red display but me. I was proudly the one with the noisy clicking keys during tests.

[@louistournas120]

Nice to see this device. I had a small mechanical multimeter when I was 15 y old. I had this kind of idea myself. If I can somehow stick a mirror on the galvanometer, I could bounce a laser beam off it. I could project it onto a wall 10 m away. However, I did not have a laser.

[@barrymayson2492]

Remember using them at school bloody difficult to get it to settle a bang on the desk and it would fly off the scale!!

[@Dukers2300]

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

[@generatorjohn4537]

Fran, That block of wood I believe is actually referred to as "micarta". It has decent insulation qualities as long as it doesn't soak up moisture. GE, Westinhouse used this product for many years in all kinds of electrical products. Another fine video BTW.

[@ermennda]

I have read "How the world was one" by Arthur C. Clarke. There he tells a very interesting story about how the first trasansatlantic cable was laid and the use of this instrument. It is fascinating to see it at work.

[@ve3krp]

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

[@seanbatiz6620]

Quite fascinating! I wonder how that reproduction company would’ve packaged something as delicate as that, during the mid 50’s, in preventing the hyper sensitive “meter” portion from getting jostled out of calibration during shipment?

[@bucyruserie1211]

Great video Fran!!!!

[@andygozzo72]

there were some Pye mirror galvanometers (later devices than that one,though)at both my middle and upper school in physics!

[@frankowalker4662]

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

[@Jm4steam]

Used and had to calibrate a lot of those.

[@trespire]

History of instrumentation, history worth remembering.

[@1027sterling]

This is so sensitive that it would be fun to put the inputs on earth ground and a long wire antenna with a diode. The changes in the electrical environment caused by the sun's magnetism could be correlated to space weather- maybe even predicting auroral activity. But likely only in a remote area without much rf interference.

[@RolandElliottFirstG]

That Ti caalculator you have on the left is identical to the one I still have, Reverse polish notation scientific, wow, thats why I bought it back in the 70's.

[@jondhuse1549]

My HP calculators use RPN... didn't know if a TI used it, too...

[@RolandElliottFirstG]

@@jondhuse1549 This model did

[@jondhuse1549]

Cool - I guess it didn't really catch on...

[@ReinoGoo]

@H Higgins RPN? Just like Forth. Stack based, no variable names.