Amazing 19th Century Tech - The Galvanometer 

That’s so cool! Thanks for sharing!

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

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.

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

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.

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

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.

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 :)

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.

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.

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

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

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

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

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.

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.

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.

The movement is a gold ribbon real gold!

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.

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.

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

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!

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.

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

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

Great to see you back

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!

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

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!

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

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!

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

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

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.

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.

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!

Welcome back Fran. Glad you are feeling refreshed.

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.

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:)

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

good to see you looking so well

Good to see you back. Another fascinating video!

Ohh Frans collection, great xxx

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

Great video Fran!!!!

Fran, You are awesome for sharing this!

Thank you Fran

Very interesting device! Thanks Fran!

Great video Fran. Thanks.

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

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. 👀👍

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

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

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!

Fascinating device. Thanks for sharing.

Love your videos Fran.

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

You look refreshed 🙏💗🥰

Very good ! Thanks.

Love your videos!

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.

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

Excellent, a real happy strangely fascinating video. Thank you

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!

thanks Fran great explanation

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

Glad you are thriving.

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

Hi Fran, sensational you always bringing news.

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

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

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

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 .

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).

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.

Love your vids!

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.

Hi Fran, so good to see you 😸

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

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

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

Thanks fran

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

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

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

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

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

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.

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

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.

That would epitomize frustration on rough seas.

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.

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.

Fran, you look great.

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!

You always have the coolest things : )

I love Fran's Texas instruments calculator.

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

Very cool!

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.