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USB Oscilloscope — Parallax Forums

USB Oscilloscope

AndyhAndyh Posts: 13
edited 2005-03-22 00:26 in BASIC Stamp
I bought a Parallax USB scope and I now have a few questions about how to use it for my work.
·
1.· I need to·examine noise on top of power supply voltage.· 5V and 10 Vdc.· This USB scope apparently cannot be set to AC coupled, so with 100 mV vertical I can't see the trace.

2.· How to calibrate the scope range, or span.· "Calibration" only adjusts the zero.· It reads 9.91 V when my dvm reads 10.090.·

Maybe I expected too much for $130 ...

Andyh

Comments

  • Doug PientakDoug Pientak Posts: 16
    edited 2005-03-22 00:26
    To AC couple the signal all you need is a .1uF (.01uF would work to)·capacitor (mono or ceramic works best) connected in series with the probe and the signal you want to measure.· This will eliminate the DC component and you will be able to use the 100mV scale to see the ripple on a 30V power rail.· Also make sure the cap. you use is rated for the DC voltage you are measuring.·
    The current software does not have calibration for the span (or dynamic range).· I am working on new software at the moment and I might add this later.· Really this scope is not accurate enough for measurements that require calibration.·
    If you would like to help beta test the new software email me at : dpientak@parallax.com.·
    The reason I suggest this is the new software has a variable dot persistence mode that is great for looking at noise.·
    Hope this helps,
    Doug
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