LOW FREQUENCY ELECTRIC FIELD SENSOR

摘要

A low frequency electric field sensor in which the two plates of the capacitive sensor are each connected to a charge amplifier causing an identical voltage to form across an output of low impedance. The amplifier and detector circuitry is enclosed between the plates to minimise noise. The voltage from the differential charge amplifier, is amplified and the data is either digitised and recorded or may be modulated and transmitted at a high frequency to an external receiver where it is digitised and stored. The use of wireless transmission avoids the noise created by using cables to the external device. Noise from the voltage amplifier is minimised by optimising the physical separation of the charge and voltage amplifiers within the box bounding sensor. The transmitter, for example, an FM modulated VHF band, is also enclosed within the sensor bounds using sufficient frequency to escape but not affect the voltage measurement at low frequencies.