PCSU02 (Software?) issues AC coupling to measure AC ripple

I’m trying to read AC ripple on a DC signal but the graph always show the combined signal DC+AC and not the AC ripple around zero value (so without the DC component). In the software I can choose between AC coupling or DC but choosing one or the other does not have any effect on the graph, it always give the combined value.

Actually, it did once gave the AC ripple around zero volts for both channels, but after switching back to DC I cannot get the AC ripple graph back anymore. It looks like a software issue, but as im new with scopes I can’t exclude the possibility of me doing something stupid :slight_smile:

I’m using Win 10 64 bits. Downloaded the software from the Velleman site, version 1.02.

Anyone got ideas? Thanks for your time.

There are relays used in the oscilloscope for the AC/DC coupling.
Very strange if both of the relays (on CH1 and CH2) have been damaged…
Even slight overvoltage (>30V) should not damage the relays.

Can you test in other PC?

I just tested on other machine and it is the same. When I press the AC button for the first time, it changes to voltage measurements around the zero voltage axis, when I then press DC button it changes back to DC(+AC) but when I press the AC button again nothing changes. DC voltage still displayed. I can see filtered AC voltage for both channels only once.

I made some screen captures.

  • First one: This is normal voltage reading, DC+AC:
  • Second one: When I press the AC button the first time the displayed voltage drops to around the zero value
  • Third one: When I press the AC button the second time the displayed voltage does not change anymore. It shows DC + AC voltage, but the AC button is activated

Obviously there is not much AC voltage ripple going on in these examples (only few mV) because I was measuring the DC output of a power adapter now, but when I choose AC it should go back to zero even in that case.

I also tried:

  • Uninstalling, rebooting and reinstalling the software. Then the AC button does not work the first time either. So whatever goes wrong after the first AC measurement is not undone by uninstalling.
  • Running the software with Windows 7 compatibility mode

Thank you for the detailed report.
I’m sorry, it seems that your PCSU02 is defective.
Please return it to the shop where you bought it to arrange for a replacement.

Alternatively you can return it for inspection to:

Velleman Tech. Dept.
Legen Heirweg 33
9890 Gavere