troubleshooting: Analog Discovery sudden breakdowns

[SimonK]

Dear Ladies and Gentlemen

Im trying to measure a Sine-Wave from a BLDC-Motor which I drive by another Motor (for a Power-Plant-Simulation).

After a random Time (from 5 secs up to 15 min) I get the following Error Message:

After clicking OK the Device disappears from the Device-Manager, but reappears within 20 secs.

A research after the Error-ID was not succesful. It happens both on my Laptop (Win10) and on my Tower (Linux), therefore I guess its not an USB-Driver Problem.

When I measure the Wave of a self crated Sine-Wave with the intern Wave-Generator, the Error does not occur.

The Sine-Wave Peaks are around +/- 3 V.

I tried decoupling the Signal with a Comparator, which I supply with 5VDC, in Order to avoid short high Peaks (which are not visible, but maybe there are...) but had no success.

With the Oscilloscope (a Big One) from my buddy it works just fine, but I cant have it for this school-project because he needs it at work...

I hope you can help me, Im looking forward for your answers

sinceresly

Simon

 

[attila]

Hi @SimonK

This could be some USB cable contact issue or excessive power transfer over the cable.
Could you provide more information about you setup? like a photo?
In order to measure the signals from the motor you also need to have a ground connection to the AD2. On the BNC adapter the shielding is connected to ground, with the wire kit you have to use a black wire. The ground of AD is connected to the PC over the USB cable. High currents over the cable ground or supply wire could disturb the communication.

[SimonK]

Good Evening attila

I solved the problem: It was a weak USB-Port in both cases (win and Linux). Found it out by Turning the Voltage Supply of the AD on and Measured with the Oscilloscope without attaching Earth to the AD. This gave me the Following result:

The yellow Line is the Ground of the Analog Discovery, the blue ist Voltage Supply (Pin V+).

Using a self-powered USB-Hub helped.

The only things I wonder is why did it breakdown after a while and not instantly?

And why is there a 50Hz disturbance on these Lines? Measuring the USB-Ports without attaching the AD did not have any disturbance...

Thank you very Much

Simon

 

[attila]

Hi @SimonK

Without common ground or reference between the oscilloscope and the tested circuit you can see such disturbance.
The scope (in DC mode) shows the voltages relative to its ground. If the ground of the circuit under test is not the same as the scope you will see the difference between the grounds plus the signal...
The 50/60Hz comes from the power line.