Sending screen error

cosmok82
Posts: 10
Joined: Thu Oct 17, 2013 2:53 pm

Re: Sending screen error

Post by cosmok82 »

jye1 wrote:Thank you. But the link couldn't be opened either.
Ok, this is the last experiment, now you must be able to see it ;) !!
This is a chinese server.
jye1
Posts: 1228
Joined: Wed Feb 20, 2013 4:58 pm

Re: Sending screen error

Post by jye1 »

Thank you for the effort! But it still said "video can not be found".
cosmok82
Posts: 10
Joined: Thu Oct 17, 2013 2:53 pm

Re: Sending screen error

Post by cosmok82 »

jye1 wrote:Thank you for the effort! But it still said "video can not be found".
After lots difficulties I re-uploaded it on YouKu. Touch wood!
jye1
Posts: 1228
Joined: Wed Feb 20, 2013 4:58 pm

Re: Sending screen error

Post by jye1 »

Thank you! I saw the video finally. For the issue I'd suggest you first check the scope with some DC source of known voltage (like a battery or regulated power supply). This is to verify that the gain/attenuation of analog channel is correct. If the gain is correct then reproduce the issue. Touch connectors, slide switches (the upper two) to see if there is connection problem. You can also measure the DC voltage of test signal with a multimeter. The reading should be around 2.5V. If you get value lower then it could be the test signal problem.
cosmok82
Posts: 10
Joined: Thu Oct 17, 2013 2:53 pm

Re: Sending screen error

Post by cosmok82 »

jye1 wrote:Thank you! I saw the video finally. For the issue I'd suggest you first check the scope with some DC source of known voltage (like a battery or regulated power supply). This is to verify that the gain/attenuation of analog channel is correct. If the gain is correct then reproduce the issue. Touch connectors, slide switches (the upper two) to see if there is connection problem. You can also measure the DC voltage of test signal with a multimeter. The reading should be around 2.5V. If you get value lower then it could be the test signal problem.
I checked the voltage on oscilloscope screen with a 3.3v bus pirate DC source and It was ok!

Then, I checked the 500Hz signal output from oscillo and I found this values.
Image
That's ok.

Then, I gave on oscilloscope's input a 1KHz square signal with bus pirate, and I found it.
Image
That's ok.

But, when I connected the oscilloscope's input to 500Hz test signal the same problem was presented.

Any solutions?
jye1
Posts: 1228
Joined: Wed Feb 20, 2013 4:58 pm

Re: Sending screen error

Post by jye1 »

Do you know the amplitude of 1KHz signal for bus pirate? If it matches the scope reading then scope is good. The amplitude of test signal could be wrong.

You have checked the frequency of test signal. But correct frequency doesn't mean the amplitude is correct.
cosmok82
Posts: 10
Joined: Thu Oct 17, 2013 2:53 pm

Re: Sending screen error

Post by cosmok82 »

jye1 wrote:Do you know the amplitude of 1KHz signal for bus pirate? If it matches the scope reading then scope is good. The amplitude of test signal could be wrong.
The amplitude of 1KHz signal for bus pirate is 3.3V and it matches!
You have checked the frequency of test signal. But correct frequency doesn't mean the amplitude is correct.
You can see the correct amplitude of signal measured on second line of multimeter. Please do more attention to upper picture!
jye1
Posts: 1228
Joined: Wed Feb 20, 2013 4:58 pm

Re: Sending screen error

Post by jye1 »

Sorry, I hadn't enlarge the photo and thought that was a frequency meter.

Does the voltage reading change if the meter is connected to the signal long time? I ask this question because, from the video, the signal was normal at beginning.

Otherwise, If scope is good and signal is good then the problem must be the probe. You can verify by connecting the test signal to scope input directly with a short wire. Just solder it right on the pads.
cosmok82
Posts: 10
Joined: Thu Oct 17, 2013 2:53 pm

Re: Sending screen error

Post by cosmok82 »

jye1 wrote:Sorry, I hadn't enlarge the photo and thought that was a frequency meter.

Does the voltage reading change if the meter is connected to the signal long time? I ask this question because, from the video, the signal was normal at beginning.

Otherwise, If scope is good and signal is good then the problem must be the probe. You can verify by connecting the test signal to scope input directly with a short wire. Just solder it right on the pads.
I did what you tell me and all gone well for 45-60 seconds, but after... the signal gone down.

I don't know what it mean... :?
jye1
Posts: 1228
Joined: Wed Feb 20, 2013 4:58 pm

Re: Sending screen error

Post by jye1 »

This is really strange. Can you please check the voltage again after the signal goes down? Also, does the scope display changes if you probe on a constant voltage for long time?
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