Wrong Voltage

DanielJ

What's wrong with my PropScope? I just got it and was trying
it out be measuring a simple 6V battery. When I set the voltage
level (y axis index) to 5V it displays the correct value (6.56V).
When I set the voltage level to 1V or 2V it displays the battery
value as 5.05V. Any suggestions would be greatly appreciated.

DanielJ

Let me be a little more specific since I was a tad frustrated before:

I was measuring an ~6V signal. Just turning the circuit on and off to
get a feel for the PropScope software (version 1.0.4) commands. Everything
was working fine. It was displaying a flat line at 6.56V at all voltage scale
settings.

I clicked on the Zoom command and then double-clicked the mouse in the window.
The double-click is a habit from some other graphics software I use. The
tool tried to zoom in really close and then displayed an arithmetic error.
I had to exit the software. When I went back in the system it would no longer
display the signal as ~6V. Instead it would only report 5.05V. I then noticed
the behavior of switching the voltage scale as described in my first post.

So, I don't know if this a software error or something else is going on. I can't
really say if the Zoom command had anything to do with anything. But either
way, it is frustrating...

hover1

I recreated the zoom function problem, but I didn't get an error message. I just hung the program. I believe the problem is the zoom function is looking for two different coordinates, (upper left and lower right). When you double click, it is using the same coordinates. This may return a value of zero when the program calculates the size of the box.

That's my theory on that problem. Not sure on your other problem.

Jim

Hanno

Hi Daniel,
Apologies about the PropScope issues. I'll fix the "zoom" double-click problem in v1.05.

I'm pretty sure the problem is related to the input divider's clipping ranges. The PropScope application draws the ground line, and the positive/negative clipping regions- as well as your signal trace. At 1x Gain, DC coupling, and a vertical resolution of 5v/div, it can read from -10..10 volt. At 2v/div, this range decreases to -5..5v. So, inputting a 6v signal will get clipped to 5v. The reason it's not exactly 5v is that all scopes are calibrated for their slightly different characteristics at the factory.

Moral of the story: If you see your signal getting close to the "clipping" bars, time to switch to a higher vertical resolution...
Hanno

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Co-author of the official Propeller Guide- available at Amazon
Developer of ViewPort, the premier visual debugger for the Propeller (read the review here, thread here),
12Blocks, the block-based programming environment (thread here)
and PropScope, the multi-function USB oscilloscope/function generator/logic analyzer

DanielJ

Hanno, Thanks for the information! You hate to feel like you already broke your new toy. I'll remember to set the scale appropriately in the future.

Jim, Thanks for the additional verification of the zoom problem.

Dan