I have a problem with the capacitance value change in bus with some wires when I touch it by hand.

I don't know if the change is because of the leakage current and how to solve this problem to have the fix capacitance value.


closed as unclear what you're asking by Dmitry Grigoryev, Edgar Brown, Sparky256, Finbarr, JYelton Feb 15 at 20:37

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  • \$\begingroup\$ What is the sensor or impedance , and signal characteristics on the wires? \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Feb 13 at 14:14
  • \$\begingroup\$ What is the problem that you are trying to fix? What effect does the changing capacitance have on the operation of your circuit? \$\endgroup\$ – Reinstate Monica Feb 13 at 15:53

The capacitance of an unshielded conductor will change as you move other conductors (like a hand) near it. You can prevent the change of capacitance by shielding them with a grounded conductor that is fixed in position.

  • \$\begingroup\$ Thanks a lot. this bus is used on cloth on wearable sensors with some sensors and four wires(about 50 cm length). I have used the isolated wires to keep the capacitance constant when it is wet. could you please help me how i can add the grounded conductor to solve the problem with the capacitance value change in contact with other conductors? \$\endgroup\$ – Ashkan Feb 14 at 14:59
  • \$\begingroup\$ Instead of individual wires, use coax, something like RG178, which is small, cheap and readily obtainable. Ground the outer, use the inner as your conductor. This will prevent the capacitance varying with position, wet, anything. However, this will result in significantly increased capacitance. That's the price you pay, small and variable, or larger and fixed. \$\endgroup\$ – Neil_UK Feb 14 at 16:12
  • \$\begingroup\$ Actually we have problem on sewing section and we need to use Ultra thin insulated connecting wire that is also slippery enough for sewing the wire. Is there any other sugestion that after sewing the wires on the tape do the shielding part to have more stable capacitance values? \$\endgroup\$ – Ashkan Feb 15 at 10:29
  • \$\begingroup\$ 'need to use ultra thin ...' Shielding consists of another flat conductor over and under the wire. Depending on your need for thin wire, if you can't tolerate RG178, you certainly won't be able to tolerate a strip of alli foil above and below. What is the precise application? Why does the variable capacitance matter? There may be alternative solutions. \$\endgroup\$ – Neil_UK Feb 15 at 10:34
  • \$\begingroup\$ the capacitance will effect on signal of the wires that will receive by the other side. My aim is to reduce the effect of the leakage current of capacitances during the wires to the signals. \$\endgroup\$ – Ashkan Feb 15 at 13:20

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