# Analog scope in X-Y mode

Discussion in 'General Electronics Chat' started by atferrari, Apr 9, 2015.

1. ### atferrari Thread Starter AAC Fanatic!

Jan 6, 2004
2,663
783
Analog oscilloscope in X-Y mode.

I am not sure how to quantify this based on the scope bandwith, 5 MHz:

I locate the beam inside a grid of 200x200 values by applying any of 200 possible steps (0 to +3V range) to each axis.

Beam initially located at (50,50). My questions:

a) How long it will take to get the beam at (150,150)?
b) How long to reach 0,150?
c) How long to reach 150,0?
d) How long for the three cases above if I start at (0,0)?

I do not have my analog scope with me right now but spent some time wondering how could I actually measure this by myself. (I am affraid it is way too abvious).

2. ### MrAl Distinguished Member

Jun 17, 2014
2,551
515
Hi,

You probably need to know the scope rise time as the bandwidth is a separate spec.
You could apply that for the vertical deflection.
For the horizontal though im not sure if you could use the same spec or not. You might look for the spec for the horizontal deflection too and see if it is different.
Theoretically we could do this if we had both time constants. It would be just a two dimensional time constant problem instead of one.

3. ### atferrari Thread Starter AAC Fanatic!

Jan 6, 2004
2,663
783
Early wake up or you did not go to bed yet?

Thanks for replying. So I need to find out both rise times. The manual or nothing, then. Hope I can get one.

Still wondering if I could (measure/test) it by using the scope itself. I couldn't imagine a way yet of how to do it.

4. ### DickCappels Moderator

Aug 21, 2008
2,755
665
You can get a pretty close estimate of risetime from this relationship.

This means that your spot will go from 10% of its way toward its destination to 90% of the way in about 0.34/5 Mhz = 68 nanoseconds.

5. ### alfacliff Well-Known Member

Dec 13, 2013
2,449
428
a scope with xy mode should have the same gain and bandwidth for both horizontal and vertical stages. imagine trying to get a phase picture of a color tv signal with different amps in each channel.

6. ### MrAl Distinguished Member

Jun 17, 2014
2,551
515
Hello,

Well some scopes have different plug in's for the vertical and horizontal, so rather than state that they will always be the same i would feel more comfortable stating that the user should consult the manufacturers spec on each amplifier.

7. ### MrAl Distinguished Member

Jun 17, 2014
2,551
515

Hi,

To test, theoretically, you would apply a perfect step voltage and see how long it takes the trace to go from 10 percent to 90 percent of the final level. In practice however, the wavefront will not be perfect, so it would be good to test a known source such as a high speed TTL family square wave using a much better scope to measure the rise time of the source. You could then apply that to your scope with the same source.
Since you seem to be using a 5MHz scope, you may be ok to just use a F family TTL gate to generate the wave. You could then see what the rise time was. You could do the same with the horizontal, if you generate a ramp on the vertical yourself. I think this would work because the 5MHz scope is probably much slower than F family TTL outputs.

8. ### alfacliff Well-Known Member

Dec 13, 2013
2,449
428
yes, using a spectrum analyzer plugin and a diferential plug in may not work very good for xy display, use sense when choosing configuration for your scope.