# What is the purpose of an oscilloscope? **URL:** \ **Category:** Factual Questions\ **Created:** [January 8, 2007, 11:59am UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-an-oscilloscope/387137 "2007-01-08T11:59:10Z")\ **Posts on this page:** 14\ **Page:** 2
**Author:** ![Crafter\_Man](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crafter_man/32/458_2.png) [@Crafter\_Man](https://boards.straightdope.com/u/Crafter_Man)\ **Post date:** [January 9, 2007, 1:59am UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-an-oscilloscope/387137/21 "2007-01-09T01:59:29Z")
[QUOTE=Absolute] Oscilloscopes are cool - but [logic analyzers](http://www.testequipmentconnection.com/HP/HP_16702B.jpg) are even cooler. [/QUOTE] Perhaps. But in my line of work, I find that a **curve tracer** is the most useful diagnostic tool when performing an autopsy on a piece of electronic harware. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [January 9, 2007, 2:27am UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-an-oscilloscope/387137/22 "2007-01-09T02:27:11Z")
> [@](#): > > If you have an oscilloscope, a computer, and a few light pens, you can make your own video game. Behold Spacewar, the coolest thing going in 1962. > > Spacewar was not the first video game. That honor apparently goes to Tic-Tac-Toe on the EDSAC a decade earlier. (It’s vaguely possible there were video games earlier.) It was, however, the first action-oriented video game, and it may be the earliest influential video game. (Nolan Bushnell, father of Atari and the video game industry, saw it, tried and failed to bring it to the masses under the name Computer Space, and went on to invent Pong.) Actually, as the American Heritage Magazine of Science and Invention reported several years ago, and this site confirms, there was an oscilloscope version of Ping Pong extant in 1958. No attempt, AFAIK, was made to market it, but apparently it was set up for lab visitors to play with: > [@](#): > > While not the first electronic game, the earliest form of an electronic ping-pong game dates back as a game played on an oscilloscope, by William A. Higinbotham at the Brookhaven National Laboratory in 1958. His game was titled Tennis for Two. > **[Pong](https://en.wikipedia.org/wiki/Pong)** > > Pong is a 1972 sports video game developed and published by Atari, Inc. for arcades. It was created by Allan Alcorn as a training exercise assigned to him by Atari co-founder Nolan Bushnell. Bushnell and Atari co-founder Ted Dabney were so surprised by the quality of Alcorn's work that they decided to manufacture the game. Bushnell based the game's concept on an electronic ping-pong game included on the Magnavox Odyssey, the first home video game console; in response, Magnavox later sued Atari... By the way, this site and several others cite Ralph Baer, not Nolan Bushnell, as the father of Pong. I don’t know the truth, myself. ---
**Author:** ![Rick](https://avatars.discourse-cdn.com/v4/letter/r/9f8e36/32.png) [@Rick](https://boards.straightdope.com/u/Rick)\ **Post date:** [January 9, 2007, 4:48am UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-an-oscilloscope/387137/23 "2007-01-09T04:48:42Z")
[QUOTE=danceswithcats] A good automotive technician does much of his or her diagnosing with an O-scope. When presented with a problem car, scoping all inputs to the ECM lets you see what is in and out of range. When I worked for Allen Testproducts, a garage owner showed me a no start car on which he’d replaced the throttle body, fuel filter, and fuel pump, without success. Yes, he was a shotgun repair fellow. I scoped the distributor pickup, expecting a square wave, and saw flat line. Because of the bad pickup, the ECM didn’t see the engine turning, so why supply fuel? 😉 [/QUOTE] We used to have a lab scope card in our diagnostic computers, but when the units were upgraded, there were no lab scope cards that would work. So after much searching and testing we distributed one of [these babies](http://buy1.snapon.com/catalog/item.asp?P65=&tool=diagnostics&item_ID=77743&group_ID=1357&store=snapon-store&dir=catalog) to each of our United States and Canadian dealers. I got to help buy about 500 O-scopes. The really cool part about this scope is that it includes known good patterns for the tech to reference to. ---
**Author:** ![Voyager](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/voyager/32/133_2.png) [@Voyager](https://boards.straightdope.com/u/Voyager)\ **Post date:** [January 9, 2007, 6:22am UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-an-oscilloscope/387137/24 "2007-01-09T06:22:41Z")
[QUOTE=Derleth] If you have an oscilloscope, a computer, and a few light pens, you can make your own video game. [Behold Spacewar, the coolest thing going in 1962.](http://wheels.org/spacewar/index.html) [Spacewar was not the first video game. That honor apparently goes to Tic-Tac-Toe on the EDSAC a decade earlier.](http://www.thocp.net/software/games/early_years.htm) (It’s vaguely possible there were video games earlier.) It was, however, the first action-oriented video game, and it may be the earliest influential video game. (Nolan Bushnell, father of Atari and the video game industry, saw it, tried and failed to bring it to the masses under the name Computer Space, and went on to invent Pong.) [/QUOTE] Spacewar did not run on an oscilloscope, but on the big display CRT hooked up to the PDP-1 in MIT Building 26. I took an assembly language class on that machine, where the final project was to play the Game of Life on the scope. If it didn’t flicker, you got an A. I think I played Spacewar once. Did Bushnell ever see SpaceWar, or did he just read about it? I also played Computer Space - and early version was put into the MIT Student Center, and our Logic Design class made a field trip across Mass. Ave to see it. As for real scopes, I have nothing to add. My worst moment with them was trying to see a 150 MHz signal (fast in 1973) on a 100 MHz scope. The best signal I saw all summer was from coupling from the flourescent lights. I look at logic analyzer signals all the time, but others collect them. ---
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [January 9, 2007, 10:56am UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-an-oscilloscope/387137/25 "2007-01-09T10:56:50Z")
Day before yesterday, another fellow wanted to detect vibration in a machine and I suggested a magnet, a hand-wound coil, and an oscilloscope. My first Oscope experience was adjusting trimpots on 555 timers in a 7400 series circuit to get the right delay between steps in an automation sequence. We used Tektronix 535 scopes - big, heavy ones with tubes - and counted reticle divisions between the trigger on channel 1 and another line on channel 2. I have a beautiful old CRT out of a DuMont oscilloscope. This thing has two electron guns and two sets of deflection plates (oscilloscope CRTs generally use electrostatic beam deflection rather than the electromagnetic deflection used in televisions, for some reason I never have heard). Thus it has two independent channels without chopping or alternating the sweeps. It can even do two XY displays - you could have duelling lissajous figures. ---
**Author:** ![Derleth](https://avatars.discourse-cdn.com/v4/letter/d/b9e5f3/32.png) [@Derleth](https://boards.straightdope.com/u/Derleth)\ **Post date:** [January 10, 2007, 9:46am UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-an-oscilloscope/387137/26 "2007-01-10T09:46:53Z")
[QUOTE=CalMeacham] Actually, as the American Heritage Magazine of Science and Invention reported several years ago, and this site confirms, there was an oscilloscope version of Ping Pong extant in 1958. No attempt, AFAIK, was made to market it, but apparently it was set up for lab visitors to play with: [/quote] The site cited in my post claims the 1958 Ping Pong game didn’t influence anyone because so few people saw it. Bushnell and Baer came up with Pong without knowledge of the earlier work. To wit: > [@The site](#): > > (Though many refer to this as the original Pong, it is an invention in isolation. Higinbotham never patented this game and no one beyond those who saw the device at the open house ever heard of it. His invention serves as a clever use of technology, but without recognition of its potential, Higinbotham’s “Tennis For Two” had no direct impact on the evolution of video games.) > [@](#): > > By the way, this site and several others cite Ralph Baer, not Nolan Bushnell, as the father of Pong. I don’t know the truth, myself. Here I might actually be wrong. I read my site as saying Bushnell invented it and Baer implemented it. I should have mentioned Baer regardless, however. > [@Voyager](#): > > Spacewar did not run on an oscilloscope, but on the big display CRT hooked up to the PDP-1 in MIT Building 26. From my other site: > [@](#): > > The first CRT display was a converted oscilloscope used to play SpaceWar. I honestly don’t know who to believe, you or the webpage. I’m dragging my cite into this to show I didn’t pull the idea out of my ass. ---
**Author:** ![Crafter\_Man](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crafter_man/32/458_2.png) [@Crafter\_Man](https://boards.straightdope.com/u/Crafter_Man)\ **Post date:** [January 10, 2007, 1:23pm UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-an-oscilloscope/387137/27 "2007-01-10T13:23:43Z")
[QUOTE=Napier] Day before yesterday, another fellow wanted to detect vibration in a machine and I suggested a magnet, a hand-wound coil, and an oscilloscope. [/QUOTE] Why not use an accelerometer? ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [January 10, 2007, 4:21pm UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-an-oscilloscope/387137/28 "2007-01-10T16:21:12Z")
[QUOTE=Napier] …oscilloscope CRTs generally use electrostatic beam deflection rather than the electromagnetic deflection used in televisions, for some reason I never have heard… [/QUOTE] Simpler construction which results in lower cost and greater robustness, primarily. 'Scope tubes are long and slender compared to TV CRTs, so they can get away with using electrostatic deflection, since they don’t require the large angle of deflection required in a TV tube which electromagnetic coils can provide. ---
**Author:** ![Kevbo](https://avatars.discourse-cdn.com/v4/letter/k/e47774/32.png) [@Kevbo](https://boards.straightdope.com/u/Kevbo)\ **Post date:** [January 11, 2007, 2:17pm UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-an-oscilloscope/387137/29 "2007-01-11T14:17:36Z")
[QUOTE=Napier] (oscilloscope CRTs generally use electrostatic beam deflection rather than the electromagnetic deflection used in televisions, for some reason I never have heard). [/QUOTE] I seldom find reason to argue with **Q.E.D.** on things electronic, but this is such a case. While it might be possible to use coils if cost were no object, it would be a royal pain for practical, rather than economic reasons: Magnetic deflection coils have fairly high inductance. In a raster scanned display, the horizontal scanning happens (in a fast computer display) at a few tens of kiloHertz, and the vertical scan at a few tens of Hertz. At these frequencies, it is manageable to supply enough voltage to drive the inductive sweep coils, though during the horizontal “fly-back” (return from right to left edge of screen, usually) The HD coil generates a high voltage spike that is captured, fed through a transformer, and used to supply the ~25-50 kilovolt acceleration voltage. The horizontal sweep device must withstand this spike, and that device was still a tube well past the point where everything else in the sets (except the CRT itself) had been replaced with solid state devices.Later, the sweep transistors were one of the least reliable components in a display, as the flyback voltage was very near the bleeding edge of transistor devleopment. In contrast to the raster display’s **kilo** Hertz scan rate, a cheap oscilloscope needs to sweep the beam at several tens of **mega** Hertz and a good one in the low hundreds. This would require extremely high voltage to force the current to rapidly change in inductive deflection coils…orders of magnitude more than a raster display. Even vacuum tubes can only handle a few KV of plate voltage. Electrostatic deflection plates, while somewhat capacitive, (which leads to higher drive **current** requirements) are much more manageable in this case. As **Q.E.D**. says, the CRT tubes that use them are long necked, and this allows the plates to operate with lower voltage. Essentially, the length is used as an “electron beam lever” to exaggerate the swing of the signals. Finally, it has not been mentioned that good analog scopes also had, in addition to X and Y, provisions for a Z input, which controlled brightness of the spot. Rarely used, but essential if vector graphics were on the table. The Z input can have MUCH more bandwidth than the X and Y, as no deflection devices (neither plates nor coils) are being driven. This fact is exploited in the fastest of all oscilloscope-like devices, the optoelectronic [streak camera](http://en.wikipedia.org/wiki/Streak_camera) . ---
**Author:** ![Jinx](https://avatars.discourse-cdn.com/v4/letter/j/c6cbf5/32.png) [@Jinx](https://boards.straightdope.com/u/Jinx)\ **Post date:** [January 12, 2007, 2:42am UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-an-oscilloscope/387137/30 "2007-01-12T02:42:37Z")
Wow! I didn’t understnad much fromt hese replies! I guess I’m cut out to stay in the mechanical world. 😃 ---
**Author:** ![Jinx](https://avatars.discourse-cdn.com/v4/letter/j/c6cbf5/32.png) [@Jinx](https://boards.straightdope.com/u/Jinx)\ **Post date:** [January 12, 2007, 2:45am UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-an-oscilloscope/387137/31 "2007-01-12T02:45:09Z")
Wow! I didn’t understand much from these replies! I guess I’m just cut out to stay in the mechanical world. ☹ ---
**Author:** ![CurtC](https://avatars.discourse-cdn.com/v4/letter/c/ce73a5/32.png) [@CurtC](https://boards.straightdope.com/u/CurtC)\ **Post date:** [January 12, 2007, 3:34am UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-an-oscilloscope/387137/32 "2007-01-12T03:34:32Z")
[QUOTE=Jinx] Wow! I didn’t understnad much fromt hese replies! I guess I’m cut out to stay in the mechanical world. 😃 [/QUOTE] [QUOTE=Jinx] Wow! I didn’t understand much from these replies! I guess I’m just cut out to stay in the mechanical world. ☹ [/QUOTE] Apparently so! ---
**Author:** ![danceswithcats](https://avatars.discourse-cdn.com/v4/letter/d/9e8a1a/32.png) [@danceswithcats](https://boards.straightdope.com/u/danceswithcats)\ **Post date:** [January 12, 2007, 6:42am UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-an-oscilloscope/387137/33 "2007-01-12T06:42:25Z")
[QUOTE=Rick] We used to have a lab scope card in our diagnostic computers, but when the units were upgraded, there were no lab scope cards that would work. So after much searching and testing we distributed one of [these babies](http://buy1.snapon.com/catalog/item.asp?P65=&tool=diagnostics&item_ID=77743&group_ID=1357&store=snapon-store&dir=catalog) to each of our United States and Canadian dealers. I got to help buy about 500 O-scopes. The really cool part about this scope is that it includes known good patterns for the tech to reference to. [/QUOTE] Sweet stuff. What I could never figure out was why a shop owner would spend a gazillion dollars on a machine, instead of enrolling all of his technicians in a few classes, at a fraction of the price. ---
**Author:** ![Rick](https://avatars.discourse-cdn.com/v4/letter/r/9f8e36/32.png) [@Rick](https://boards.straightdope.com/u/Rick)\ **Post date:** [January 12, 2007, 1:11pm UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-an-oscilloscope/387137/34 "2007-01-12T13:11:15Z")
Our shops do both. Some tools are considered manditory to be able to repair our cars, and we send them out automatically and bill the dealers for them. This scope was one of those tools. The dealers are also required to meet minimum training standards for the technicians in the shop. Some dealers send their guys willingly, others um not so. But in the end the guys do get trained. On this scope, I teach a two day class where it is no lecture all shop time looking at patterns, how to set up the scope, what you are looking at, and where to go next. This is one of the more fun classes for me to teach. [Previous page](https://boards.straightdope.com/t/what-is-the-purpose-of-an-oscilloscope/387137.md?page=1)