Patent ID: 8860401

Claim:
A high impedance electric potential sensor comprising: a detection electrode for detecting electrical potentials from an object under test and for generating electrical detection signals, an amplifier connected to the detection electrode for receiving the electrical detection signals from the detection electrode and for producing an amplified measurement signal as output; the amplifier having at least one ancillary circuit providing a positive feedback arrangement for enhancing sensitivity of the electric potential sensor to detected electrical potentials, the at least one ancillary circuit including a bootstrapping circuit for providing bootstrapping to an input bias resistor for the amplifier; and a negative feedback arrangement for the amplifier to control sensitivity of the electric potential sensor to signals of differing frequency in order to tailor a frequency response of the electric potential sensor, the negative feedback arrangement comprising an active narrow band filter situated in a negative feedback path from the output to the input of the amplifier, and tuning circuitry for tuning the filter to a selected frequency or selected frequencies, whereby to tune the frequency response of the electric potential sensor with respect to at least one of the detection signals generated by an object under test and unwanted signals representing interference so as to increase an amplitude of the detection signals relative to an amplitude of unwanted interference signals whereby to increase an effective dynamic range of the electric potential sensor.