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external file storage and use as reference

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external file storage and use as reference

Postby thsharris » Mon May 14, 2012 6:49 pm

I'm trying to save a waveform in PS6 for use as a test reference (output) signal. I need to test some control systems that use 0-to-5 v analog input centered at 2.5 volts. The goal is to feed the control system a reference signal of known definition (frequency, amplitude) to measure/monitor the response of that system. Straightforward stuff w/ no high frequency or high voltage or any tricks. A sine wave at various frequencies from fractional Hz to a few Hz w/ 2.5 volt offset shouldn't be too much to ask, should it?

It is proving problematic for several reasons:

PS6 Crash during CSV file format save

Will write .MAT format but won't read it

Waveform generator won't generate a wave form w/ more than a 1 volt offset.

Using math channels to generate some combination of terms to get the 2.5 v offset doesn't allow for either the frequency sweep or simply saving in some readable format.

The only (single!?!) reference to these issues are in the forum from 2009, which really does NOT give me a warm a fuzzy. Have these issues existed so long and never been addressed, or is there a workaround using the PicoLog suite? This simple test task of generating a low voltage low frequency waveform in some sort of stored format for playback as an external reference on demand should be trivial at this level of lab test/measurement tool. I hope it doesn' t take a huge patchwork of partial fixes or bandaids to achieve this type of solution, but initial efforts indicate that may be the case if its even possible at all!

Thank you for the help-

TH
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Re: external file storage and use as reference

Postby Hitesh » Tue May 15, 2012 8:40 am

Hi TH,

Which version of PicoScope are you using? Have you tried using the latest release (6.6.23 or 6.6.28 (Release Candidate)) or PicoScope 6 Beta?

Which device are you using? There is a limit on the offset voltage.

Regards,
Hitesh

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Re: external file storage and use as reference

Postby thsharris » Tue May 15, 2012 8:18 pm

I've got 6.6.28.1 running and have tried the Beta 6.7 but the install failed a few times while I was on the phone distracted from the effort. I think 6.6 was running when I tried the install...?

I can get the preferred +2.5v DC offset on a reference channel by putting the frequency sweep harmonic on the GEN output and adding 2.5 in the math channel to achieve that reference, but that means that my GEN is busy w/ a sine wave about 0 volts center and already used up in the effort, so I have to record the 'mathed' reference for later (reading and) playback. Then the problem becomes writing and being able to read both in the same format. I don't have MathLab but it looks like I might need some additional tools to get where I need to go.

This is low current TTL shell CMOS hardware I'm trying to feed the analog voltage to centered at 2.5v. I'm not trying to drive any DC motor with it or anything. Strictly low current.

If Beta 6.7 gives me better DC offset ability (or either way actually), I need to sort out that install bug. I'm using VMWare Fusion 4.1.2. on an iMac Intel Core Duo 3+GHz w/ 12 GB of 1.06 GHz ram. Sounds exciting but doesn't solve problems without plenty of coaching!

Are PicoLog Recorder and PicoLog Player possibily going to be my saving tool segments in this journey of discovery?

Thanks again for the help

Mr. Harris
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Re: external file storage and use as reference

Postby thsharris » Tue May 15, 2012 8:24 pm

Sorry - its a 3206B purchased in 2011.
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Re: external file storage and use as reference

Postby Hitesh » Mon May 21, 2012 10:01 am

Hi Mr. Harris,

Unfortunately, the PicoLog software will not work with the PicoScope 3206B.

The 3206B oscilloscopes are limited to a voltage range of +/- 2 Volts and this is likely to be a result of limit provided by the USB input of 5V.

I think you would have to have some kind of circuitry to modify the signal to achieve what you are looking to do.

Regards,
Hitesh

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