A Coulombmeter is a tool for measuring the

electrostatic Electrostatics is a branch of physics that studies electric charges at rest (static electricity). Since classical times, it has been known that some materials, such as amber, attract lightweight particles after rubbing. The Greek word for amber ...

charge of a material. A Coulombmeter is used in combination with a

Faraday cup A Faraday cup is a metal (conductive) cup designed to catch charged particles in vacuum. The resulting current can be measured and used to determine the number of ions or electrons hitting the cup. The Faraday cup was named after Michael Faraday w ...

or a metal probe for taking charge measures of a material. A Nanocoulombmeter is a Coulombmeter that is capable of measuring electrostatic charge down to the accuracy of a fraction of a nanocoulomb (nC). Electrostatic charge on an object can be measured by placing it into the Faraday Cup. The charge is transferred to the cup and displayed on the meter's display. The Faraday Cup of the Coulombmeter has an outer, grounded metal shield that surrounds an inner

electrode An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte, a vacuum or air). Electrodes are essential parts of batteries that can consist of a variety of materials de ...

. The inner electrode, which is electrically isolated from the shield, is connected to a meter to measure the charge. In the field of

semiconductor A semiconductor is a material which has an electrical resistivity and conductivity, electrical conductivity value falling between that of a electrical conductor, conductor, such as copper, and an insulator (electricity), insulator, such as glas ...

design, a coulombmeter consists of a meter used in combination with a metal probe tip to pinpoint locations of excess charge on, for instance a semiconductor device. This application of a coulombmeter is useful because electrostatic discharge is a leading cause of failure in semiconductor chip designs, and may occur during the fabrication, inspection, assembly, and other processes. A coulombmeter allow this electrostatic buildup to be easily measured simply by applying the instrument's probe to its lead. The coulombmeter was devised in 1984 for the Revised Nuffield Advanced Physics course.Revised Nuffield Advanced Physics: Apparatus Guide by Mark Ellse, 1985, p59, Note: coulombmeter is typically written as a single word in order to avoid confusion with the measurement unit 'coulombs-meter' and also to make it easily searchable in scientific literature.

Detection of electron and ion beams

A nanocoulombmeter, in combination with a

, can be used to detect and measure the beams emitted from

electron gun An electron gun (also called electron emitter) is an electrical component in some vacuum tubes that produces a narrow, collimated electron beam that has a precise kinetic energy. The largest use is in cathode-ray tubes (CRTs), used in nearly ...

s and ion guns. The Faraday cup consists of a shielded cup with an aperture, which collects the kinetically active electrons or ions, and an output wire, which is connected to a nanocoulombmeter. The Faraday cup can be completely separate from the gun, or it can be part of an assembly mounted to the end of the electron/ion gun and manipulated remotely. Some Faraday cup assemblies include a

phosphor screen A phosphor is a substance that exhibits the optical phenomenon, phenomenon of luminescence; it emits light when exposed to some type of radiant energy. The term is used both for fluorescence, fluorescent or phosphorescence, phosphorescent sub ...

as well. An array of small Faraday cups or a Faraday cup on mounted on a linear manipulator can be used to measure the distribution of the beam current across the spot; this shows the beam uniformity.

References

Electrostatics Electronic test equipment Electrical test equipment Electrical meters Electronics work tools {{electronics-stub