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AC Mode measurements

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AC Mode measurements

Postby TimOster » Tue Jan 27, 2015 8:54 pm

Hi,

I'm working on a BLOCK mode example and I've got it reading DC fine. The user is prompted for Channel, Range, AC/DC and number of samples. Works fine and I'm playing around with the overFlow flags.

Now I would like to measure AC signals, however if I simply change from DC to AC in channel setup, I get nothing back.

Are there additional settings needed to read AC signals?

my basic events are:

sp2000_open_unit
prompt user for chan, range, #samples, AC or DC
ps2000_set_channel (with this info)
ps2000_run_block to collectdata
wait for ready
ps2000_get_values to pull it from the array
display the information
close unit

If it is DC I get back the ~1.6V I'm applying, but if I select AC what I see looks like there is nothing connected to the input.

Thanks for any help.

Tim
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Re: AC Mode measurements

Postby Karunen » Fri Jan 30, 2015 2:08 pm

Hi Tim,

In AC mode it tries to get rid of the DC component of a signal.

Therefore you will not see a DC signal you will just see the ripple.

Kind Regards,
Karunen

Technical Specialist
Pico Technology
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Re: AC Mode measurements

Postby TimOster » Fri Jan 30, 2015 7:14 pm

I used the Pico native app to read the signal. Then I try the project I'm working on and I get essentially nothing. Should have gotten the same number, if I'm doing it correctly.

I'm wondering if the timebase is not getting setup correctly for an AC measurement. This is what was in the blockmode example I started with (for the example I specifically asked for DC only).

'find the fastest sampling rate
While (ps2000_get_timebase(handle, timebase, noSamples, timeInterval, timeUnits, 1, maxNoSamples) = 0)
timebase += 1
End While

Thank you for your continuing help.

Tim
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Re: AC Mode measurements

Postby Karunen » Tue Feb 03, 2015 9:52 am

Hi Tim,

Can you send me a screen shot of the measurement you are expecting to see either here or to support@picotech.com?

Please note the measurements are a PicoScope 6 software addition.
And are that data cannot be pulled from the driver.

So if I am clear when you use the drop down circled below in PicoScope 6 you get different values from what you get using your application?
ACmode.PNG
AC/DC mode dropdown
ACmode.PNG (2.39 KiB) Viewed 1565 times


If so can you tell me what driver you are using?

Kind Regards,
Karunen

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Pico Technology
Karunen
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