1
\$\begingroup\$

Been looking into doing from preliminary work on EMC testing in house prior to sending various bits of machinery to certification labs. One suggestion is that we carry out the testing in an EMC tent as a cheap option for the full chamber. However, even a small one about the size of my desk is around £2200.

So, how viable is a DIY version made from (at worst) cardboard with standard aluminium kitchen foil glued to it and grounded?

\$\endgroup\$
2
  • \$\begingroup\$ What frequency range are you wanting the tent to be effective for and what type of testing will you do? \$\endgroup\$
    – Andy aka
    Commented May 1, 2018 at 15:45
  • \$\begingroup\$ @Andyaka Probably from about 10MHz to around 1GHz, maximum of 10V/m. At present we have a piece of equiment failing at 0.5V/m at above 100MHz due to lack of shielding on PT100 probe \$\endgroup\$
    – Dirk Bruere
    Commented May 1, 2018 at 15:59

1 Answer 1

Reset to default
1
\$\begingroup\$

Overlap the foil by 50%. That is, lay down foil edge-to-edge, then place a 2nd layer centered over joints of the first layer. The capacitance between layers will be enormous

C = Eo * Er * Area/Distance

C = 9 * Ef of air (The aluminum oxide should not dominate) * 1 meter^2 / 0.1mm

C = 10pF/meter * meter * meter/0.0001m = 10pF * 10,000 = 100,000 PF or 0.1uF

Thus at 1MHz the layer/layer capacitance will be ~ 1.6 ohms at 1MHz.

\$\endgroup\$
2
  • \$\begingroup\$ Foil thickness and attenuation? \$\endgroup\$
    – Dirk Bruere
    Commented May 2, 2018 at 8:29
  • 1
    \$\begingroup\$ The idea comes from Interferrence Technology yearly conference writeup, in an article on EMP protection using foil inside a room. Key was: lay down one layer of foil, edge to edge, and simply staple to the wall; then lay down a 2nd layer of foil, offset 50% from the first layer to cover the seams, and staple that layer atop the first layer. Since the aluminum oxide prevents conductive current movements, the high-speed currents travel via CAPACITIVE coupling, which I computed for you. Use regular kitchen foil. I would not pretend to compute the attenuation of foil at 10MHz EMP pulse-width. \$\endgroup\$
    – analogsystemsrf
    Commented May 3, 2018 at 4:41

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.