Electrostatic voltmeter
Encyclopedia
Electrostatic Voltmeter can refer to an electrostatic charge meter, known also as Surface DC Voltmeter, or to an electrical potential measuring voltmeter
, traditionally called Electrostatic Voltmeter.
transfer.
It can accurately measure surface potential (voltage
) on materials without making physical contact and so there is no electrostatic charge transfer or loading of the voltage source
.
Explanation
Many voltage measurements cannot be made using conventional contacting voltmeter
s because they require charge transfer to the voltmeter, thus causing loading and modification of the source voltage. For example, when measuring voltage distribution on a dielectric
surface, any measurement technique that requires charge transfer, no matter how small, will modify or destroy the actual data
.
Principle of operation
In practice, an electrostatic charge monitoring probe
is placed close (1 mm to 5 mm) to the surface to be measured and the probe body is driven to the same potential
as the measured unknown by an electronic circuit
. This achieves a high accuracy measurement that is virtually insensitive to variations in probe-to-surface distances. The technique also prevents arc-over
between the probe and measured surface when measuring high voltages.
, it is, however, designed to measure high potential differences; typically from a few hundred to many thousands volts.
Principle of operation
The electrostatic voltmeter is utilizing the attraction force between two charged surfaces to create a deflection of a pointer directly calibrated in volts. Since the attraction force is the same regardless of the polarity of the charged surfaces (as long as the charge is opposite), the electrostatic voltmeter can measure both direct current
and alternating current
.
Typical construction is shown in the engraving. The pivoted sector NN is attracted to the fixed sector QQ. The moving sector indicating the voltage by the pointer P and is counterbalanced by the small weight w. In newer instruments the weight is replaced by a spring, thus allowing the meter to be used both in horizontal and vertical positions. This form of design is shown in the photograph of the mechanism. The fixed sector is insulated from the rest of the meter. The butterfly shaped moving sector, made out of a thin aluminum foil, is pivoted below. Both the fixed and the moving sectors are highly polished and without any sharp corners to minimize high electrical stress areas. The movement of the sector is damped by the air vane attached by a curved piece of wire.
Voltmeter
A voltmeter is an instrument used for measuring electrical potential difference between two points in an electric circuit. Analog voltmeters move a pointer across a scale in proportion to the voltage of the circuit; digital voltmeters give a numerical display of voltage by use of an analog to...
, traditionally called Electrostatic Voltmeter.
Surface DC Voltmeter
An Surface DC Voltmeter is an instrument that measures voltage with no electric chargeElectric charge
Electric charge is a physical property of matter that causes it to experience a force when near other electrically charged matter. Electric charge comes in two types, called positive and negative. Two positively charged substances, or objects, experience a mutual repulsive force, as do two...
transfer.
It can accurately measure surface potential (voltage
Voltage
Voltage, otherwise known as electrical potential difference or electric tension is the difference in electric potential between two points — or the difference in electric potential energy per unit charge between two points...
) on materials without making physical contact and so there is no electrostatic charge transfer or loading of the voltage source
Voltage source
In electric circuit theory, an ideal voltage source is a circuit element where the voltage across it is independent of the current through it. A voltage source is the dual of a current source. In analysis, a voltage source supplies a constant DC or AC potential between its terminals for any current...
.
Explanation
Many voltage measurements cannot be made using conventional contacting voltmeter
Voltmeter
A voltmeter is an instrument used for measuring electrical potential difference between two points in an electric circuit. Analog voltmeters move a pointer across a scale in proportion to the voltage of the circuit; digital voltmeters give a numerical display of voltage by use of an analog to...
s because they require charge transfer to the voltmeter, thus causing loading and modification of the source voltage. For example, when measuring voltage distribution on a dielectric
Dielectric
A dielectric is an electrical insulator that can be polarized by an applied electric field. When a dielectric is placed in an electric field, electric charges do not flow through the material, as in a conductor, but only slightly shift from their average equilibrium positions causing dielectric...
surface, any measurement technique that requires charge transfer, no matter how small, will modify or destroy the actual data
Data
The term data refers to qualitative or quantitative attributes of a variable or set of variables. Data are typically the results of measurements and can be the basis of graphs, images, or observations of a set of variables. Data are often viewed as the lowest level of abstraction from which...
.
Principle of operation
In practice, an electrostatic charge monitoring probe
Probe
- Science and technology :* Medical equipment** Anal probe** Endoscope** Proctoscope* Atom probe, an atomic-resolution microscope* Hybridization probe or chemical probe, used in molecular biology...
is placed close (1 mm to 5 mm) to the surface to be measured and the probe body is driven to the same potential
Potential
*In linguistics, the potential mood*The mathematical study of potentials is known as potential theory; it is the study of harmonic functions on manifolds...
as the measured unknown by an electronic circuit
Electronic circuit
An electronic circuit is composed of individual electronic components, such as resistors, transistors, capacitors, inductors and diodes, connected by conductive wires or traces through which electric current can flow...
. This achieves a high accuracy measurement that is virtually insensitive to variations in probe-to-surface distances. The technique also prevents arc-over
Electrical breakdown
The term electrical breakdown or electric breakdown has several similar but distinctly different meanings. For example, the term can apply to the failure of an electric circuit....
between the probe and measured surface when measuring high voltages.
Electrostatic Voltmeter
Electrostatic Voltmeter operating principle is similar to that of an electrometerElectrometer
An electrometer is an electrical instrument for measuring electric charge or electrical potential difference. There are many different types, ranging from historical hand-made mechanical instruments to high-precision electronic devices...
, it is, however, designed to measure high potential differences; typically from a few hundred to many thousands volts.
Principle of operation
The electrostatic voltmeter is utilizing the attraction force between two charged surfaces to create a deflection of a pointer directly calibrated in volts. Since the attraction force is the same regardless of the polarity of the charged surfaces (as long as the charge is opposite), the electrostatic voltmeter can measure both direct current
Direct current
Direct current is the unidirectional flow of electric charge. Direct current is produced by such sources as batteries, thermocouples, solar cells, and commutator-type electric machines of the dynamo type. Direct current may flow in a conductor such as a wire, but can also flow through...
and alternating current
Alternating current
In alternating current the movement of electric charge periodically reverses direction. In direct current , the flow of electric charge is only in one direction....
.
Typical construction is shown in the engraving. The pivoted sector NN is attracted to the fixed sector QQ. The moving sector indicating the voltage by the pointer P and is counterbalanced by the small weight w. In newer instruments the weight is replaced by a spring, thus allowing the meter to be used both in horizontal and vertical positions. This form of design is shown in the photograph of the mechanism. The fixed sector is insulated from the rest of the meter. The butterfly shaped moving sector, made out of a thin aluminum foil, is pivoted below. Both the fixed and the moving sectors are highly polished and without any sharp corners to minimize high electrical stress areas. The movement of the sector is damped by the air vane attached by a curved piece of wire.