jg001
Newbie level 6
Hi,
We are trying to design a readout circuit for a capacitive sensor. The capacitive sensor itself is only a fraction of a pF and the changes in its capacitance due to some mechanical input is in the fF range. On top of these small values, two restrictions (no compromise) have been imposed on the readout circuit:
1) It has to be 10s of feet away from the sensor (connected via a multi-wire cable)
2) One end of the capacitive sensor must be grounded
With such small capacitance value to have to work with, my guess is that just the parasitic capacitance from the cable will be 100s of pF connected in parallel with the sensor itself, which will severely degrade the sensitivity of my output.
So, does anyone have any idea on how to compensate for this relatively large parasitic capacitance? I've thought of using negative impedance converters (NICs), but PSPICE simulation says it will not work.
I have attached a two-page PDF (mostly circuit diagrams) which will give the reader some background info and my NIC implementation attempt. Thanks in advance for any suggestions.
-- JG
We are trying to design a readout circuit for a capacitive sensor. The capacitive sensor itself is only a fraction of a pF and the changes in its capacitance due to some mechanical input is in the fF range. On top of these small values, two restrictions (no compromise) have been imposed on the readout circuit:
1) It has to be 10s of feet away from the sensor (connected via a multi-wire cable)
2) One end of the capacitive sensor must be grounded
With such small capacitance value to have to work with, my guess is that just the parasitic capacitance from the cable will be 100s of pF connected in parallel with the sensor itself, which will severely degrade the sensitivity of my output.
So, does anyone have any idea on how to compensate for this relatively large parasitic capacitance? I've thought of using negative impedance converters (NICs), but PSPICE simulation says it will not work.
I have attached a two-page PDF (mostly circuit diagrams) which will give the reader some background info and my NIC implementation attempt. Thanks in advance for any suggestions.
-- JG