[murphy625]

I just bought a tektronics 465B.. Seems to work with calibration signal just perfectly.

I bought it so I could see the encoder signals on my servo motor.

OK. here is the problem..

When the motor is turning VERY slow, I get a nice square wave.

When I speed the motor up to a few hundred RPM, I can not get that same square wave to show. I get something that looks like a modulated FM signal actually.
I tried the high / low frequency rejections but it didnt help..

Here is what I find strange....
When I attached the probe, I can only hook up to the A+ wire as there is no way to hook up to the A-.. Dont I need the A- for a ground or something?

Am I not supposed to hook up the A+ and A- at the same time? I am under the impression that the A+ channel is "signal high" and the A- channel is "signal common".. In order to see the A+, dont I need to probe the A+ and ground to the A- ??

Im a little confused.


Any ideas?

Murphy

[lerman]

I assume that the encoder has differential signals. That means that the signal is represented by the DIFFERENCE between the two values.

IIRC, the 465B is a dual channel scope. So, you should connect the A to one channel and the A- to the other channel. Then set the scope in A-B mode (I think that is what it is called). That will display the difference between the two channels. The ground from at least one of the probes should be connected to ground.

Make sure that the trigger is set properly (to trigger on the signal). Also, as the speed increases, you will have to set the sweep frequency higher. (I know this is pretty basic, but I don't know what your background is.)

Since I don't know the mechanical arrangement you have, I can't suggest a way to get to the A- signal.

Ken

[Al_The_Man]

I have a similar model and Techtronix refer to Ch1 & Ch2 you should be able to see two channels at once without alternating, but in your case I would assume you just want to observe one channel? If so the probe should have the the ground wire coming off just below the probe end, which you will need to connect, also your problem may be because of the sync switch is not set to trigger on the channel you are using, and in that case the display will free-wheel and high frequencies will look like a blur.
Al

[murphy625]

I got it. ... Thanks!!!!!!

I was triggering on AUTO....

Thanks again.
Murphy