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how do I invert a channel

Discussion forum for the new Picoscope Linux software

how do I invert a channel

Postby buttercup » Wed Jun 08, 2016 12:37 pm

I would like to invert a channel using PicoScope for Linux but can’t figure out how to do it.
In the Windows version I can define a probe with a scale factor of * - 1 but I don’t think can define a probe in the Linux version.
The Linux version allows me to scale a channel but it does not seem to accept negative values.
An alternative method would be to select a pre-defined probe that inverts but the available list of probes does not contain an inverting probe.

My Software version is (6.11.13.3)
I am using Ubuntu 15.04

Apart from this very minor issue I am really pleased with Picoscope for Linux.
I am technician at a Further Education college.
Previously it proved very difficult to get our computer suppliers to install software on our Windows PCs (we are not allowed admin access to these PCs).
Now we have a couple of “old” PCs in each lab running Ubuntu and all is good and everybody is happy.

Thanks for all you hard work getting PicoScope running with Linux.
buttercup
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Re: how do I invert a channel

Postby Hitesh » Thu Jun 16, 2016 8:28 am

Hi buttercup,

The PicoScope 6 for Linux software currently does not support Custom probes or Math Channels. However, if you save a data file or settings file with a Custom Probe using PicoScope 6 for Windows, you should be able to use the probe in the Linux version.

I will put in a request to our Development Team (it is planned to achieve feature parity with the Windows version).

What sort of signals are you capturing?

Regards,
Hitesh

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Re: how do I invert a channel

Postby buttercup » Fri Jun 17, 2016 8:59 am

Thanks for the workaround Hitesh, 8)
I’ll experiment with creating custom probes using a windows laptop and copy the setup file.

Our students are investigateing the current voltage relationship of inductors and capacitors with a range of frequencies.
I'm using a 1K resistor as a shunt to measure current in mA.
The resistor and reactive component are in series and fed by a signal generator (with a floating output not referenced to earth).
The Picoscope input earth connections go the connection between the resistor and reactive component and the inputs to channels A & B go to each of the outputs from the signal generator.
The lecturer says it doesn’t matter so much that the current channel is inverted because the students are only investigating the amplitude relationship at the moment.

It might be worth Pico technology marketing a suitable amplifier for education users. It would be handy if such a thing had a BNC input and maybe 4mm output connectors so that colleges and schools could use Picoscope as a frequency generator with low output impedance. Not sure how well this would sell though?

Our lecturing staff will get excited if you get the maths channels working with Linux!
Using a windows PC we have been playing around with the maths channels and a pendulum hanging from a potentiometer.
The potentiometer output gives angular displacement. A differentiation function gives angular velocity and double differentiating the input gives angular acceleration.
It appears to be necessary to filter the signal pretty heavily each time before differentiating but since the students only investigate the pendulum over a small range of frequencies this does not present a problem.

Tanks again,
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Re: how do I invert a channel

Postby buttercup » Fri Jun 17, 2016 11:48 am

I've just saved the default Picoscope settings from my Windows PC and copied the default.PSSETTINGS file from the Windows PC to a Linux PC.
An invert channel I created on the Windows PC is now available on the Linux PC (and it works) so my problem of how to invert a channel is solved.
Surprisingly the maths channel I created on the windows PC now appear on the Linux PC so it looks like Picoscope on Linux is just missing the graphics front end to be able to define maths channels
I think (for the time being) I will want to copy across a default.PSSETTINGS file without the maths channels because its not obvious how to delete them on the Linux PC.

Thanks again Hitesh
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Re: how do I invert a channel

Postby Hitesh » Mon Jun 20, 2016 9:53 am

Hi buttercup,

I have put forward the suggestion, although you should be able to obtain an amplifier from a third party seller.

You can also load in Maths channels as you have found. If the Linux version has implemented the option to hide channels via the Views menu option then you could use this to hide Maths channels although the number of samples that can be collected would still be limited to 5 MS.

Regards,
Hitesh

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