Faraday Cup Electrometer

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The Faraday Cup electrometer (abbreviation: FCE ) is the simplest form of electrical measuring device for particle measurement of aerosols .

function

It consists of an electrometer and a filter inside a Faraday cage , also called a Faraday cup . Charged particles that are collected by means of the filter change the potential of the Faraday's beaker. Since the Faraday cup is kept at a constant potential, the captured ions (electrons) must be neutralized by electrons, which can flow into or out of the Faraday cup via a connected high-resistance resistor (typically 10 ⁹ - 10 ¹¹ Ω). A voltage therefore drops across the resistor, which is a measure of the ion current (electron current) and is e.g. B. can be measured with an amplifier / electrometer.

application

The Faraday-Cup Electrometer can be used in aerosol research to measure the average charge of an aerosol. For this purpose, a further, independent determination of the number concentration is required. However, if the charge state of an aerosol is known, the FCE can be used to determine the number concentration, which is then directly proportional to the measured current.