A null method for electric field measurement

Electric field measurements in the atmosphere must overcome two problems:the electric fields are present across the extremely high impedance of atmospheric air, and natural meteorological variations lead to a considerable dynamic range of electric fields. These two factors conflict when using semiconductor amplifiers because devices with low input current cannot offer a large dynamic range. A method of extending the dynamic range of sensitive amplifiers is described here, by using the sensitive device purely as a null detector between the input potential and a variable high voltage supply, adjusted by negative feedback. This transfers the dynamic range requirement from the amplifier to the high voltage supply. The input amplifier can operate with an input current of less than 10(-14)A, and the system has a dynamic range of +/-500V although in principle this could be greatly increased. The system was designed for use with an atmospheric passive antenna system, but it may have more widespread applications.