Hi everyone.
We are paying for our sins trying to couple a standalone device we designed 6+ years ago with a Windows-running tablet as a display/control device.
The device we have passes everything by itself just fine.
Now it was decided to use a tablet as a display (before it had none) plus to be able to download parameters etc.
During the CE certification while conducting conducting (no pun intended) immunity test it was observed that the tablet reacts to noise in 300kHz / 700kHz range (obviously no ferrites help at these frequencies). Even though this does not interrupt the cycle the device is running continuously and the tablet recovers nicely when the test is stopped with no operator intervention, for these tests (unlike for ESD / EFT where criteria B is used, recovery with no operator intervention) no reaction manifesting itself is allowed at all.
It should be noted that the device uses a 12V power supply with a regular 2.5mm barrel power DC jack where the minus is also the MAINS Protection Ground. This power supply is used because the same tablet would misbehave with the fully isolated Power Supply when subjected to ESD test (it would sometimes go dark and then after a couple of minutes would agree to be powered up by pressing the power button). It actually might probably behave nice during conducted immunity with it but then we'd fail ESD.
I am not sure what I could do here. I even looked for something that could be sold to be plugged in series with USB cables to clean the surges but nothing really small enough in size has been found.
Could appreciate some fresh ideas (short of selling the device and the tablet separately. Could be done but .... uncouth).
There is a PDF file attached showing the simplified diagram of the things connected.
We are paying for our sins trying to couple a standalone device we designed 6+ years ago with a Windows-running tablet as a display/control device.
The device we have passes everything by itself just fine.
Now it was decided to use a tablet as a display (before it had none) plus to be able to download parameters etc.
During the CE certification while conducting conducting (no pun intended) immunity test it was observed that the tablet reacts to noise in 300kHz / 700kHz range (obviously no ferrites help at these frequencies). Even though this does not interrupt the cycle the device is running continuously and the tablet recovers nicely when the test is stopped with no operator intervention, for these tests (unlike for ESD / EFT where criteria B is used, recovery with no operator intervention) no reaction manifesting itself is allowed at all.
It should be noted that the device uses a 12V power supply with a regular 2.5mm barrel power DC jack where the minus is also the MAINS Protection Ground. This power supply is used because the same tablet would misbehave with the fully isolated Power Supply when subjected to ESD test (it would sometimes go dark and then after a couple of minutes would agree to be powered up by pressing the power button). It actually might probably behave nice during conducted immunity with it but then we'd fail ESD.
I am not sure what I could do here. I even looked for something that could be sold to be plugged in series with USB cables to clean the surges but nothing really small enough in size has been found.
Could appreciate some fresh ideas (short of selling the device and the tablet separately. Could be done but .... uncouth).
There is a PDF file attached showing the simplified diagram of the things connected.
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