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Passive Components
Forum Any help on the following low pass filter scenario would be very much appreciated.
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Related

Any help on the following low pass filter scenario would be very much appreciated.

k.morrow
k.morrow 11 months ago

Objective: To build a shielded cable with a passive low pass filter to be used for connecting the ground connection of a typical US 120V socket or from an earth  ground rod to a bed sheet with silver threads in it for grounding or earthing purposes. The purpose is for the filter to eliminate any/all AC noise from going up the shielded cable and getting to the bed sheet.
For testing possible filter configurations I have a Fluke 179 True RMS multimeter and an old Hitachi V-152F-15MHz Oscope and a BK 3011B - 2 MHz Function generator.

My thoughts are to use a single resistor with an electrolytic capacitor so when measured with the multimeter in one direction I would measure the resistor value and in the other direction I would measure an infinite impedance.

I have explored several online low pass filter calculators:
www.redcrab-software.com/.../RC-Low-Pass-Filter
sim.okawa-denshi.jp/.../CRlowkeisan.htm
learningaboutelectronics.com/.../Low-pass-filter-calculator.php
markimicrowave.com/.../

I have a few questions:
1. Do I make the filter with a cutoff frequency of 60Hz or something very low like 1Hz or less?
2. Is an RC filter best or use an RLC or some other config?
3. Could the filter be better with a 2nd order (or 3rd, or 4th ...?).
4. For the filter connected to a shielded cable, are surface mount components better to use than leaded components?

Thank You!!

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Top Replies

  • dougw
    dougw 11 months ago +1
    If the only connection is ground, what are you filtering with respect to? I'm not sure you can do better than a direct connection to ground to minimize capacitive, inductive or RF coupling to the sheet…
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  • k.morrow
    k.morrow 11 months ago

    I am trying to eliminate any AC noise that is on the house ground from going up the shielded cable to the conductive bed sheet.

    I have attached a picture of what I want to do.

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  • k.morrow
    k.morrow 11 months ago in reply to k.morrow

    It is the same concept as hooking up an ESD mat except I'm trying to filter any and all noise on the cable from the wall outlet ground to the ESD mat.

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  • k.morrow
    k.morrow 11 months ago in reply to k.morrow

    It is the same concept as hooking up an ESD mat except I'm trying to filter any and all noise on the cable from the wall outlet ground to the ESD mat.

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  • anniel747
    anniel747 11 months ago in reply to k.morrow

    How did you measure that noise?

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