Who needs a scope? - Page 1
Forum section: electronics / projects

author: itdontgo
author_rank: Regular Contributor
timestamp: January 22, 2016, 09:10:19 pm
content: How about this for an acoustic Oscilloscope? Just needs a trigger!

author: trevwhite
author_rank: Frequent Contributor
timestamp: January 22, 2016, 09:23:49 pm
content: That is excellent!

author: Falcon69
author_rank: Super Contributor
timestamp: January 22, 2016, 09:36:07 pm
content: That has got to be one of the coolest things I've seen.I had no idea the strings vibrate like that. Good song too.

author: awallin
author_rank: Frequent Contributor
timestamp: January 22, 2016, 09:44:46 pm
content: I have a feeling that the actual motion of the strings is much simpler. The linked video above, and many others on youtube, show an aliasing effect due to the limited fps of the camera.real motion is a bit like this maybe

author: HAL-42b
author_rank: Frequent Contributor
timestamp: January 22, 2016, 10:35:58 pm
content: Fun fact: The most sensitive and fastest responding galvanometer ever was not the mirror galvanometer as it is widely believed. In fact it was the String Galvanometer invented by Dr. Willem Einthoven in 1901.https://en.wikipedia.org/wiki/Willem_EinthovenDr. Einthoven invented the string galvanometer because he had a task - He wanted to measure the beat of the heart. In order to do this he needed to invent a device sensitive enough to do just that - record the human heartbeat before any sort of electrical amplification even existed.DeForest's Audion tube was in 1906, remember.Thus he invented the ECG without electronic amplification and got a Nobel prize for it in 1924.This is what won a Nobel Prize in 1924, and this is photograph of a vibrating string.His galvanometers were so sensitive that it is said there are no clearer ECG graphs taken with by any other equipment, even today.In order to achieve that sensitivity Endhoven's galvanometers had to be massive water cooled behemoths. They working was based on Lenz's Law - a current carrying object placed in a magnetic field moves sideways, and not towards one of the poles. This was extremely counterintuitive to me for very long time.And you still had to observe the string trough a microscope or project it on a moving film in order to get a graph.The funniest thing was that how Eindhoven produced the string for his galvanometer. Obviously, the thinner the string is the more sensitive the apparatus will be. So he manufactured his strings from pure quartz and then coated them with gold or silver in order to make them conductive. TThe filament was originally made by drawing out a filament of glass from a crucible of molten glass. To produce a sufficiently thin and long filament an arrow was fired across the room so that it dragged the filament from the molten glass. The filament so produced was then coated with silver to provide the conductive pathway for the current. By tightening or loosening the filament it is possible to very accurately regulate the sensitivity of the galvanometer.So this is how guitars and oscilloscopes and strings and bows with arrows tie up in my sleep deprived mind.

author: dom0
author_rank: Super Contributor
timestamp: January 23, 2016, 12:24:32 am
content: QuoteThat's some serious heavy metal science.

author: joeqsmith
author_rank: Super Contributor
timestamp: January 23, 2016, 10:09:48 am
content: QuoteWow

author: timb
author_rank: Super Contributor
timestamp: January 24, 2016, 12:35:49 am
content: Someone has to have done this with a multi-thousand FPS camera. That would show the true string movement and remove the aliasing, right?

author: miguelvp
author_rank: Super Contributor
timestamp: January 24, 2016, 03:35:01 am
content: Quote from: timb on January 24, 2016, 12:35:49 amMaybe this can do the job at 1 trillion FPSMore info:http://video.mit.edu/watch/visualizing-video-at-the-speed-of-light-one-trillion-frames-per-second-9742/

author: timb
author_rank: Super Contributor
timestamp: January 24, 2016, 09:30:38 am
content: Quote from: miguelvp on January 24, 2016, 03:35:01 amHmmm, that might not work, actually! It uses a laser and moveable mirror to scan a scene over time and then uses the data to reconstruct what happens at the photon level. So, it needs a still scene to do the job. It's like a sampling oscilloscope, when what we need is a realtime one.Pretty cool non the less. I'd read about that a few years back but didn't know they had it working!