In addition, the threads about ground noise bring their latest research results.
Once again, sorry for the English may incorrectly.
SDS7102V SN 1234XXXX
Viewed the “ground noise” correlations with switching power supply uses two channel oscilloscope.
Content is done at the same SDS7102, power produced by the battery.
The second channel is connected to ground and seen polution noise. Trigger synchronization starts on the first channel. Connected to the first channel "empty" probe. End (short needle) is used as a capacitive local antenna. When approaching the needle to the schema components can be seen local emissions. Both probes have a bandwidth of 250 MHz.
"GND noise" is already known to many owners of problem party of 7102. This chaotic sharp bursts, on closer inspection it is decaying burst with a frequency of about 100 MHz.
Below view of GND-noise emissions from various DC / DC converter power supply circuit SDS7102.
1. Converter -7.6 V. Board PSU, IC3 (chip MC34063), the frequency of about 63 kHz
Conclusion: there is a very weak ringing high-frequency of the rise edge.
I recall that in my 7102 this step-down converter is modified, reduced pollution from him (
https://www.eevblog.com/forum/testgear/review-of-owon-sds7102/msg192647/#msg192647).
2. Converter +3.3 V. Adapter board, U21 (chip ACT4060A), frequency of about 380 kHz:
Conclusion: there is a very weak overlap at the front switch. Impact is minimal.
3. Converter +2.8 V. Adapter board, the chip labeled "1780 TB51», frequency of about 1200 kHz:
Conclusion: does not bring influence.
4. Converter +8.8V. Scheme pulse LCD display backlight. Adapter board, U8 chip labeled "5126Q".
The emission of this schema has an interesting look. Short burst repetition rate of about 30 kHz. Frequency of the pulses themselves about 860 kHz (in this example, the brightness of the display is minimal - 20%).
Conclusion: The significant ringing overlap is from the fronts. Tangible impact. Because of the instability frequency converter introduced them part of the noise is a random character.
5. Converter +5.5V core supply. Adapter board, the chip is marked Z1094AI.
Synchronizing GND-noise with this converter explicit. Unfortunate "spikes" of noise is exactly the same with the rear switch fronts. There is also a previously identified high-ringing generation at frequencies around 100 MHz.
Conclusion: this converter provides the main pollution and creates "GND-noise”.