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We are doing an EMC test of a capacitance sensing touch panel, pursuant to immunity issues versus 28MHz noise. We do it in 2 methods:

  1. The operator is holding an antenna (which generates 28MHz noise) and simultaneously touching the panel to test sensing behavior.
  2. The operator is holding an antenna (which generates 28MHz noise) and another person touches the panel to test sensing behavior.

As a result, noise level monitored in method (1) is by far higher than in method (2) and it could not report relevant sensing behavior.

By what mechanism does the noise transfer from the antenna to the panel though the human body when the test operator is going to touch the panel? In general, should the operator hold the antenna during a test of sensing behavior?

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What are you testing? Assuming the touchscreen performance; you should use a camera in the anechoic chamber and use an artificial hand to touch the screen and observe the performance. I don't know the product standard exactly but as an EMC engineer that's how I would perform the test.

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  • \$\begingroup\$ I do EMS(immunity) test to test the touchscreen's tolerance under 28MHz noise radiated from an antenna. I must have to touch the screen to test it's performance, so I wonder if I should let other cooperator hold the antenna while I touch the screen? Because if I hold the antenna, noise seems to transfer though my body and affect the screen's performance. \$\endgroup\$
    – user87649
    Commented Oct 27, 2015 at 0:49
  • \$\begingroup\$ Yes it can work but your technique is completely wrong as I saw. Why you have to hold the antenna ? You should use an antenna mast to hold the antenna straight in position. A person can not hold the antenna while generating RF signal. Its not safe either not comply with the standards. Use a basic plastic/wood rod to hold the antenna. I understand your requirement to touch the screen while the electric field is generated but this is not "the" EMS testing procedure. You need an artificial hand that simulates your touching behaviour or you may code a test software to simulate touching event on th \$\endgroup\$
    – kenan
    Commented Oct 27, 2015 at 3:51
  • \$\begingroup\$ ..the screen. Otherwise being in a room while there is an electric field is not a healthy choice. I hope you're making the test with 3V/m strength. Anyway at least stick with the antenna mast. Someone holding an antenna while there is a signal is not a suitable option to choose. \$\endgroup\$
    – kenan
    Commented Oct 27, 2015 at 3:54

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