volatile signal phase

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detlef a
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Joined: Tue Feb 21, 2012 8:10 pm

volatile signal phase

Post by detlef a » Tue Feb 21, 2012 8:12 pm


I do an evaluation on the 4227. I use picoscop6, 2 Channels, no Trigger,
dc coupling, autorange, samplerate 1.5626Ms/s, 50ms acquisition time,
78130 samples per channel. I save the data in an .txt file, three columns:
time, channel 1, channel 2.
My analog signal is a 1.5Vpp sine, 200Hz from a hp signal Generator. The
signal is applied to two voltage dividers, 100R by 100R. The output signal
of the two voltage dividers is fed into the two channels of the 4227.

I analyze the two signals with a matlab script. I do a fft and calculate
the phase shift between the two signals.

I exspect a constant value, close to zero.

I do get ( 7 measurements ):
-8.6792e-004 rad, -8.2561e-004 rad, -8.8991e-004 rad, -8.9823e-004 rad,
-8.4968e-004 rad, -1.0148e-003 rad, -8.7078e-004 rad

One of the results is more than 10^-4 rad off the mean value, standard
deviation is close to 6e-5 rad.

That is to much for the anticipated use.

Do you see any flaws in the setup?
Faulty software setup?
How do I get a more constant phase delay between the channels?
The 4227 does a multiplexing, using one ADC for two channels?
Are there any other pico products with two ADCs for two channels and
constant phase delay between the channels?

Second observation:
The recorded sample timestamps from the file are not equally spaced,
though the 4227 uses uniform sampling ?! Could this be the problem?

thank you for reading


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Re: volatile signal phase

Post by Martyn » Tue Mar 06, 2012 9:00 am

Can I ask you to submit this question to support@picotech.com with a copy of the text file data you have collected.
Technical Support Manager

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