# oscilloscopes and trigonometry

Discussion in 'General Electronics Chat' started by ninjaman, Aug 7, 2016.

1. ### ninjaman Thread Starter Member

May 18, 2013
306
1
Hello,
I have a 100 MHz Iwatsu scope that I am learning how to use. I have a book called, "Use of the dual-trace oscilloscope" by Charles H. Roth, I am using this to learn about the using the scope. I have the manual for the scope which covers a few things but this other book is a lot more in depth. The problem I am having at the moment is my trigonometry is lagging a bit. I have started to learn about it but when it comes to oscilloscopes I do not know that stuff yet. One question that I don't yet understand is x = 2 + 3 cos wt and y = 1 + 3 sin wt. It asks for maximum X deflection, minimum x deflection, maximum y deflection and minimum y deflection. Then you have to sketch the limiting values, the answer is a circle mostly in the top right quadrant of the screen. I haven't yet got to cos and sin together in an equation so I don't know what this is.
For people that work in the industry, how much do you use math when working with an oscilloscope. I don't mean using the math functions on a scope, but pen and paper stuff using trigonometry and please could you post a problem that you may have come across in the past as an example.

Thanks
Simon

Apr 5, 2008
15,799
2,385
3. ### AlbertHall Well-Known Member

Jun 4, 2014
2,261
447
Early episodes of Dr Who had an ancient (it was ancient even then) oscilloscope displaying a lissajous figure inside the tardis, IIRC it was 2:1

Feb 19, 2010
3,500
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None.

5. ### WBahn Moderator

Mar 31, 2012
18,085
4,917
The key to answering the questions you were asked is to simply note that sine and cosine both vary from -1.0 to +1.0.

So x = 2 + 3cos(wt) can vary from

x = 2 + 3(-1.0) = -1

to

x = 2 + 3(+1.0) = 5

So what will y vary between?

If you have a rolling reset imager then if you take a picture of an object that is moving vertical lines will be angled by an amount that is dependent on the speed and the frame rate. That means that if the imager is working correctly, the signal corresponding to the edge in the top row of the output will be offset relative to that same edge in the bottom row by an amount that can be determined via trig and algebra. This allows you to set up a simple test system using just a scope on the analog output of the imager (instead of actually capturing an image, which is a lot more complicated) to give you a quick idea of the imager's internal circuitry is working properly.