Pico Technical Support and Discussion Forum

Hello,

we need to test the frequency response of a PI (PID)
loop and the system. To use PicoScopes would be nice,
so do you have an idea how to solve this problem ?

Best Regards,
Marco

Hello Marco,

I am curious that you wish to measure frequency response rather than step response.

You could conceivably measure the latter with one of our oscilloscopes, however, you would need to define the parameters.

Regards
John

Hi John,

for this application i need to measure the frequency
response, it is a very slow system in the range of 0.01 - 10Hz.
Step response is also important to see how the loop react to changes
in the system but this is easy to measure with an oscilloscope.
To design the loop it helps to see the transit frequency and phase,
therefor a bode plot is a nice tool. With a 2 channel scope and the build in
generator (awg) it should be possible to build up such a testsetup - what do you think ?

greetings,
marco

Hi Marco,

What you wish to achieve is technically feasible if you were to write your own application software, and your solution would be an interesting and useful addition to this forum.

You could of course simply use cursors in PicoScope to determine time difference between channels (and therefore determine phase) at various spot frequencies, which you could then plot graphically.

Regards
John

I agree, the PicoScope would be an excellent platform for Bode plots. I have put it in as a suggestion for a long time now. The manual way is just to time consuming. I have one of our software engineers looking into writing code for this. If PicoScope would do this I would be willing to work with them and spend extra for the software application just to do Bode plots. They already have some of the basic software in the spectral feature. I am also prepared to buy an upgraded scope, from the 3000 series I currently have, to a 5000 series scope.
I currently use a 2630 Tektronix Fourier Analyzer which is obsolete and we can not even get it repaired anymore. I must get something more reliable.

Hello,

so we are two persons who need such instrument
and i think there will be a lot more out there that
need Bode Plots for testing and development.

So it would ne nice to know if PICO TECH. will
include this option or not ?

As an option the Vellemann Scope + Function Generator
can perform a Bode Plot, but i don't like thier products,
so a solution from Pico would be better.

greetings,
marco

Hi Marco & Guest,

Thank you for your inputs and, I shall pass them to our product planning team for consideration.

Regards
John

Hello,

Just wanted to give a third agreement on that. I know some other scopes have that ability, and I would like my picoscope to be able to do that too.

Hello,

I'd also just like to join the club. I had a Velleman before and used its ability to record bode plots heavily. When I bought the Picoscope I just presumed it would be able to do this as well and was quite dissapointed to find it couldn't.

I get the answer "suggest it to the developers" for three years now. Could you give us a hint what they answered?

I like the scope in its other aspects, but I'm missing the bode tool badly.

There are many functions that we do want to put into PicoScope6, Bode Plots are one. The only difficulties are time and engineering resources. Unfortunately, I cannot give any indication of when, or in what order, we can roll-out new features. We are working as fast as we can!
PeterF.