Can you try using the ADC100 adapter that came with the unit. Remember to read the help file regarding this.
When you are using this adaptor you will need to tell the computer so that it recognises that it is there. To do this you need to insert the following patch into the win.ini file:
You should insert the patch on a new line and exactly as written above. When you have done this, save the file and exit. The Picoscope software should now recognise the adaptor and report "Use Adapter" in Help | About. The ADC-100 should also now be functioning normally.
This should help the units reference voltages.
If the problem persists, please contact us again.
Michael - Tech Support
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