[technut84]

I have a 20 amp emi/rf filter connected from my house outlet, which is standard U.S. current, to my high voltage, high frequency Tesla Coil.The emi filter is made to stop interference or damaging spikes from going from the house outlet into a device. However, will the filter stop spikes going FROM the Tesla coil into the house wiring? And if not, can I turn the filter around (reverse wiring) to do this? So far, no one can definitively answer this, not even the emi filter maker, which is a MAJOR electronics supplier! Thanks

[InfoJunkie4Life]

Generally speaking, an EMI/RFI filter is basically a high pass filter or choke. These are usually designed using inductors and capacitors in a symmetrically designed circuit. They provide high resistance to frequencies above the specified range. If your Tesla coil is emitting high frequency interference then your filter should act bi-directionally.

There may be other design implementations that I'm not aware of that make this null, however you can test it by emitting a high frequency from the line side and reading the results on the load side (normal use) and then from the load side and metering on the line side (reverse operation). There should be little to no reading across the filter.

You could probably use a Phone/LAN line tester that emits a tone above the specifications of the filter... I'd guess 100Hz or higher. Keep in mind these tools emit an audible noise and the human hearing range is well above the standard AC 60Hz.

[technut84]

Thank you for your info! Yes, the filter does utilize an inductor/capacitor/resistor design. I will test it as you suggest as soon as I get the proper test equipment.
Now, is there another way to test it with other equipment besides the Phone/LAN tester? And can it be done without using the house current for the test?
Thanks again for you help!

[InfoJunkie4Life]

It is purely dependent on the design of the filter. I would guess that you could test it using any sort of emitter that produces a high frequency and any receiver that is capable of reading the frequency output of the emitter. However, there may be voltage limitations that prevent this from being an accurate test. Some filters are designed with resistor/diode combinations preventing low voltages from passing through.

Sending a low dc voltage (any battery 1.5v-12v) through the filter or conducting a continuity test across the filter could verify or negate this. Or it could be a tuned band pass preventing low frequencies as well as high frequencies from passing. I would wire this filter to a 12vdc battery and use a multimeter to see if the same voltage exists on the load side. If it passes then any tester that outputs a similar voltage should be allowed through the filter except those above the filter range.

I only thought of the LAN tester because it is a common tool in my field, I am certain there must be other types of testers/tools that can achieve this test but none come to mind immediately.

[technut84]

It is purely dependent on the design of the filter. I would guess that you could test it using any sort of emitter that produces a high frequency and and any receiver that is capable of reading the frequency output of the emitter. However, there may be voltage limitations that prevent this from being an accurate test. Some filters are designed with resistor/diode combinations preventing low voltages from passing through.

Sending a low dc voltage (any battery 1.5v-12v) through the filter or conducting a continuity test across the filter could verify or negate this. Or it could be a tuned band pass preventing low frequencies as well as high frequencies from passing. I would wire this filter to a 12vdc battery and use a multimeter to see if the same voltage exists on the load side. If it passes then any tester that outputs a similar voltage should be allowed through the filter except those above the filter range.

I only thought of the LAN tester because it is a common tool in my field, I am certain there must be other types of testers/tools that can achieve this test but none come to mind immediately.

Thank you for your response, most helpful. I will perform the tests in due time and report back to this blog with the results in case others find the info useful.