Share
VIDEOS 1 TO 50
When to Use an Electrometer
When to Use an Electrometer
Published: 2015/03/08
Channel: Kerry Wong
Keithley 610C Electrometer Calibration and Experiments
Keithley 610C Electrometer Calibration and Experiments
Published: 2016/11/10
Channel: Marco Reps
Keithley 610C Electrometer Repair
Keithley 610C Electrometer Repair
Published: 2016/11/05
Channel: Marco Reps
ADA4530-1 Electrometer Op Amp: Measuring Femptoamp Currents
ADA4530-1 Electrometer Op Amp: Measuring Femptoamp Currents
Published: 2016/11/30
Channel: Analog Devices, Inc.
Electrometer-Grade Amplifier Improves Measurement Accuracy
Electrometer-Grade Amplifier Improves Measurement Accuracy
Published: 2017/03/15
Channel: Analog Devices, Inc.
Model 6517B Electrometer/High Resistance Meter Insulating Resistance Testing
Model 6517B Electrometer/High Resistance Meter Insulating Resistance Testing
Published: 2016/10/06
Channel: Tektronix
Electrometer Meaning
Electrometer Meaning
Published: 2015/04/27
Channel: ADictionary
Henley electrometer
Henley electrometer
Published: 2011/05/11
Channel: ChipDipvideo
The Keithley Situation: New Electrometer, Nixie Tube Multimeter, SMU Update
The Keithley Situation: New Electrometer, Nixie Tube Multimeter, SMU Update
Published: 2017/07/03
Channel: Marco Reps
ADA4530-1 Electrometer Op Amp with Integrated Guard Buffer
ADA4530-1 Electrometer Op Amp with Integrated Guard Buffer
Published: 2016/03/24
Channel: Avnet Electronics Marketing: Legacy
Keithley 617 Electrometer with LEAKY RELAY [PART 1] see also EEVblog #1017
Keithley 617 Electrometer with LEAKY RELAY [PART 1] see also EEVblog #1017
Published: 2017/09/25
Channel: Tom Mathews
Electrometer
Electrometer
Published: 2016/01/22
Channel: WikiAudio
#30 - Keithley 614 electrometer repair and calibration
#30 - Keithley 614 electrometer repair and calibration
Published: 2015/09/09
Channel: FeedbackLoop
Spark gap and electrometer
Spark gap and electrometer
Published: 2012/01/26
Channel: Antonio Queiroz
Electrometer
Electrometer
Published: 2008/05/17
Channel: Antonio Queiroz
Home made electrometer
Home made electrometer
Published: 2012/10/15
Channel: Happynewgeiger
Volta
Volta's condenser electrometer explanation
Published: 2008/10/02
Channel: histodid
What is FARADAY CUP ELECTROMETER? What does FARADAY CUP ELECTROMETER mean?
What is FARADAY CUP ELECTROMETER? What does FARADAY CUP ELECTROMETER mean?
Published: 2017/01/19
Channel: The Audiopedia
Electrometer
Electrometer
Published: 2017/02/05
Channel: Escher Oh
Keithley 619 2-Channel Electrometer Repair and Calibration
Keithley 619 2-Channel Electrometer Repair and Calibration
Published: 2016/12/25
Channel: Marco Reps
qLabs Hand-Held ElectroMeter for Rapid Testing
qLabs Hand-Held ElectroMeter for Rapid Testing
Published: 2016/04/21
Channel: Micropoint Biosciences
Basic Ion Chamber and Electrometer Characteristics - Part I
Basic Ion Chamber and Electrometer Characteristics - Part I
Published: 2016/01/26
Channel: Standard Imaging
Electrometer test
Electrometer test
Published: 2017/04/01
Channel: thedanyes
Keithley 6517A Electrometer
Keithley 6517A Electrometer
Published: 2008/05/23
Channel: Mike Cordi
Basic Ion Chamber and Electrometer Characteristics - Part I
Basic Ion Chamber and Electrometer Characteristics - Part I
Published: 2016/04/26
Channel: Standard Imaging
Quadrantenelektrometer,Thomson quadrant electrometer
Quadrantenelektrometer,Thomson quadrant electrometer
Published: 2015/02/06
Channel: xofunkox
Измерение МНО с помощью прибора qLabs Electrometer
Измерение МНО с помощью прибора qLabs Electrometer
Published: 2016/11/13
Channel: SAMKOM LLC
Richmann
Richmann's electrometer
Published: 2011/05/06
Channel: ChipDipvideo
Volta
Volta's condenser electrometer - explanation
Published: 2007/06/15
Channel: Lidia Falomo
Kapillarelektrometer,Capillary electrometer
Kapillarelektrometer,Capillary electrometer
Published: 2017/12/02
Channel: xofunkox
Mütter Minute: Original Piezoelectric Quartz Electrometer used by Marie Curie
Mütter Minute: Original Piezoelectric Quartz Electrometer used by Marie Curie
Published: 2011/04/11
Channel: Mütter Museum of the College of Physicians of Philadelphia
Quarzfadenelektrometer,Quartz fibre electrometer
Quarzfadenelektrometer,Quartz fibre electrometer
Published: 2017/03/21
Channel: xofunkox
Simple Science 2: Build Your Own Electrometer
Simple Science 2: Build Your Own Electrometer
Published: 2017/09/10
Channel: SSF Simple Science
Toepler machine, hailstorm boxes, and Henley electrometer
Toepler machine, hailstorm boxes, and Henley electrometer
Published: 2010/03/22
Channel: Antonio Queiroz
SuperMAX Electrometer - Setup
SuperMAX Electrometer - Setup
Published: 2013/12/19
Channel: Standard Imaging
Electrostatics 2. Henley
Electrostatics 2. Henley's Electrometer
Published: 2017/05/04
Channel: Alejandro del Mazo Vivar
Volta
Volta's condenser electrometer - operation
Published: 2007/06/15
Channel: Lidia Falomo
How to Enable the Meter Connect Feature on the Model 6517B Electrometer
How to Enable the Meter Connect Feature on the Model 6517B Electrometer
Published: 2011/01/25
Channel: KeithleyInst
6514, Keithley, Programmable Electrometer from Alliance Test
6514, Keithley, Programmable Electrometer from Alliance Test
Published: 2013/01/16
Channel: AllianceTestEquipment
Gold Foil Electrometer Demonstration
Gold Foil Electrometer Demonstration
Published: 2014/10/23
Channel: collinsunbound
High Resistance Measurements using Keithley
High Resistance Measurements using Keithley's Model 6517B Electrometer
Published: 2011/09/13
Channel: KeithleyInst
J-FET Electrometer
J-FET Electrometer
Published: 2010/01/22
Channel: dcmk1mr2
Bennet
Bennet's doubler and Henley's electrometer
Published: 2010/01/12
Channel: Antonio Queiroz
Keithley 617 Electrometer with LEAKY RELAYS [PART 2]
Keithley 617 Electrometer with LEAKY RELAYS [PART 2]
Published: 2017/10/17
Channel: Tom Mathews
Kelvin Electrometer
Kelvin Electrometer
Published: 2009/07/18
Channel: abunaii97
Keysight B2980A Series of Femto/Picoammeters and Electrometers
Keysight B2980A Series of Femto/Picoammeters and Electrometers
Published: 2014/09/01
Channel: Keysight General Purpose Instruments
Volta
Volta's condenser electrometer operation
Published: 2008/10/02
Channel: histodid
Electrometer Readings
Electrometer Readings
Published: 2017/11/01
Channel: Chi Loca
Henley electrometer with wimshurst machine
Henley electrometer with wimshurst machine
Published: 2009/04/09
Channel: Luiz Alberto Feijó Jr.
Robbery electrometer work   two person arrested
Robbery electrometer work two person arrested
Published: 2016/05/25
Channel: Lankasri News
NEXT
GO TO RESULTS [51 .. 100]

WIKIPEDIA ARTICLE

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Volta Electrometers
Kolbe electrometer, precision form of gold-leaf instrument. This has a light pivoted aluminum vane hanging next to a vertical metal plate. When charged the vane is repelled by the plate and hangs at an angle.

An electrometer is an electrical instrument for measuring electric charge or electrical potential difference. There are many different types, ranging from historical handmade mechanical instruments to high-precision electronic devices. Modern electrometers based on vacuum tube or solid-state technology can be used to make voltage and charge measurements with very low leakage currents, down to 1 femtoampere. A simpler but related instrument, the electroscope, works on similar principles but only indicates the relative magnitudes of voltages or charges.

Historical electrometers[edit]

Gold-leaf electroscope[edit]

Gold-leaf electroscope

The gold-leaf electroscope was one of the instruments used to indicate electric charge. It is still used for science demonstrations but has been superseded in most applications by electronic measuring instruments. The instrument consists of two thin leaves of gold foil suspended from an electrode. When the electrode is charged by induction or by contact, the leaves acquire similar electric charges and repel each other due to the Coulomb force. Their separation is a direct indication of the net charge stored on them. On the glass opposite the leaves, pieces of tin foil may be pasted, so that when the leaves diverge fully they may discharge into the ground. The leaves may be enclosed in a glass envelope to protect them from drafts, and the envelope may be evacuated to minimize charge leakage. A further cause of charge leakage is ionizing radiation, so to prevent this, the electrometer must be surrounded by lead shielding.[citation needed] This principle has been used to detect ionizing radiation, as seen in the quartz fibre electrometer and Kearny fallout meter.

This type of electroscope usually acts as an indicator and not a measuring device, although it can be calibrated. The Braun[dubious ] electroscope replaced[when?] the gold-leaf electroscope for more accurate measurements.[citation needed]

The instrument was developed in the 18th century by several researchers, among them Abraham Bennet and Alessandro Volta.

Early quadrant electrometer[edit]

Early quadrant electrometer.

While the term "quadrant electrometer" eventually referred to Kelvin's version, this term was first used to describe a simpler device.[1] It consists of an upright stem of wood, to which is affixed to a semicircle of ivory. From the center there hangs a light cork ball upon a pivot. When the instrument is placed upon a charged body, the stem participates and repels the cork ball. The amount of repulsion may be read off the graduated semicircle, though it is obvious that the measured angle is not in direct proportion to the charge.

Coulomb's electrometer[edit]

Coulomb electrometer

torsion to give a measurement more sensitive than repulsion of gold leaves or cork-balls. It consists of a glass cylinder with a glass tube on top. In the axes of the tube is a glass thread, the lower end of this holds a bar of gum lac, with a gilt pith ball at each extremity. Through another aperture on the cylinder, another gum lac rod with gilt balls may be introduced. This is called the carrier rod.

If the lower ball of the carrier rod is charged when it is entered into the aperture, this will repel one of the movable balls inside. An index and scale (not pictured) is attached to the top of the twistable glass rod. The number of degrees twisted to bring the balls back together is in exact proportion of the amount of charge of the ball of the carrier rod.

Francis Ronalds, the inaugural Director of the Kew Observatory, made important improvements to the Coulomb torsion balance around 1844 and the modified instrument was sold by London instrument-makers.[2] Ronalds used a thin suspended needle rather than the gum lac bar and replaced the carrier rod with a fixed piece in the plane of the needle. Both were metal, as was the suspending line and its surrounding tube, so that the needle and the fixed piece could be charged directly through wire connections. Ronalds also employed a Faraday cage and trialled photography to record the readings continuously. It was the forerunner of Kelvin’s quadrant electrometer (described below).

Peltier electrometer[edit]

Developed by Peltier, this uses a form of magnetic compass to measure deflection by balancing the electrostatic force with a magnetic needle.

Bohnenberger electrometer[edit]

The Bohnenberger electrometer, developed by J.G.F. von Bohnenberger, consists of a single gold leaf suspended vertically between the anode and cathode of a dry pile. Any charge imparted to the gold leaf

Lord Kelvin's Quadrant Electrometer

Developed by Lord Kelvin, this is the most sensitive and accurate of all the mechanical electrometers. The original design uses a light aluminum sector suspended inside a drum cut into four segments. The segments are insulated and connected diagonally in pairs. The charged aluminum sector is attracted to one pair of segments and repelled from the other. The deflection is observed by a beam of light reflected from a small mirror attached to the sector, just as in a galvanometer. The engraving on the right shows a slightly different form of this electrometer, using four flat plates rather than closed segments. The plates can be connected externally in the conventional diagonal way (as shown), or in a different order for specific applications.

A more sensitive form of quadrant electrometer was developed by Frederick Lindemann. It employs a metal-coated quartz fiber instead of an aluminum sector. The deflection is measured by observing the movement of the fiber under a microscope. Initially used for measuring star light,[citation needed] it was employed for the infrared detection[citation needed] of airplanes in the early stages of World War II.

Some mechanic electrometers were housed inside a cage often referred to as a “bird cage”. This is a form of Faraday Cage that protected the instrument from external electrostatic charges.

Electrograph[edit]

Electricity readings may be recorded continuously with a device known as an electrograph. Francis Ronalds created an early electrograph around 1814 in which the changing electricity made a pattern in a rotating resin-coated plate. It was employed at Kew Observatory and the Royal Observatory, Greenwich in the 1840s to create records of variations in atmospheric electricity.[3] In 1845, Ronalds invented photographic means of registering the atmospheric electricity. The photosensitive surface was pulled slowly past of the aperture diaphragm of the camera box, which also housed an electrometer, and captured ongoing movements of the electrometer indices as a trace.[4] Kelvin used similar photographic means for his quadrant electrometer (see above) in the 1860s.

Modern electrometers[edit]

A modern electrometer is a highly sensitive electronic voltmeter whose input impedance is so high that the current flowing into it can be considered, for most practical purposes, to be zero. The actual value of input resistance for modern electronic electrometers is around 1014Ω, compared to around 1010Ω for nanovoltmeters.[5][6] Owing to the extremely high input impedance, special design considerations must be applied to avoid leakage current such as driven shields and special insulation materials.

Among other applications, electrometers are used in nuclear physics experiments as they are able to measure the tiny charges left in matter by the passage of ionizing radiation. The most common use for modern electrometers is the measurement of radiation with ionization chambers, in instruments such as geiger counters.[citation needed]

Vibrating reed electrometers[edit]

Vibrating reed electrometers use a variable capacitor formed between a moving electrode (in the form of a vibrating reed) and a fixed input electrode. As the distance between the two electrodes varies, the capacitance also varies and electric charge is forced in and out of the capacitor. The alternating current signal produced by the flow of this charge is amplified and used as an analogue for the DC voltage applied to the capacitor. The DC input resistance of the electrometer is determined solely by the leakage resistance of the capacitor, and is typically extremely high, (although its AC input impedance is lower).

For convenience of use, the vibrating reed assembly is often attached by a cable to the rest of the electrometer. This allows for a relatively small unit to be located near the charge to be measured while the much larger reed-driver and amplifier unit can be located wherever it is convenient for the operator.[7]

Valve electrometers[edit]

Valve electrometers use a specialized vacuum tube (thermionic valve) with a very high gain (transconductance) and input resistance. The input current is allowed to flow into the high impedance grid, and the voltage so generated is vastly amplified in the anode (plate) circuit. Valves designed for electrometer use have leakage currents as low as a few femtoamperes (10−15 amperes). Such valves must be handled with gloved hands as the salts left on the glass envelope can provide leakage paths for these tiny currents.[8]

In a specialized circuit called inverted triode, the roles of anode and grid are reversed. This places the control electrode at a maximum distance from the space-charge region surrounding the filament, minimizing the amount of electrons collected by the control electrode, and thus minimizing the input current.[9]

Solid-state electrometers[edit]

The most modern electrometers consist of a solid state amplifier using one or more field-effect transistors, connections for external measurement devices, and usually a display and/or data-logging connections. The amplifier amplifies small currents so that they are more easily measured. The external connections are usually of a co-axial or tri-axial design, and allow attachment of diodes or ionization chambers for ionising radiation measurement. The display or data-logging connections allow the user to see the data or record it for later analysis. Electrometers designed for use with ionization chambers may include a high-voltage power supply, which is used to bias the ionization chamber.

Solid-state electrometers are often multipurpose devices that can measure voltage, charge, resistance and current. They measure voltage by means of "voltage balancing", in which the input voltage is compared with an internal reference voltage source using an electronic circuit with a very high input impedance (of the order of 1014 ohms). A similar circuit modified to act as a current-to-voltage converter enables the instrument to measure currents as small as a few femtoamperes. Combined with an internal voltage source, the current measuring mode can be adapted to measure very high resistances, of the order of 1017 ohms. Finally, by calculation from the known capacitance of the electrometer's input terminal, the instrument can measure very small electric charges, down to a small fraction of a picocoulomb. [1]

See also[edit]

References[edit]

  • Dr. J. Frick, Physical Technics; Or Practical Instructions for Making Experiments in Physics Translated By John D. Easter, Ph.D. - J. B. Lippincott & Co., Philadelphia 1862
  • Robert Mfurgeson Ph.D. Electricity - William and Robert Chambers, London and Edinburgh 1866
  • Silvanus P. Thompson, Elementary Lessons in electricity and Magnetism. - Macmillan and Co. Limited, London 1905
  • Jones, R. V., Instruments and Experiences - John Wiley and Sons, London 1988
  1. ^ Draper, John William (1861). A textbook on chemistry. New York: Harper and sons. p. 119. 
  2. ^ Ronalds, B.F. (2016). Sir Francis Ronalds: Father of the Electric Telegraph. London: Imperial College Press. ISBN 978-1-78326-917-4. 
  3. ^ Ronalds, B.F. (2016). Sir Francis Ronalds: Father of the Electric Telegraph. London: Imperial College Press. ISBN 978-1-78326-917-4. 
  4. ^ Ronalds, B.F. (2016). "The Beginnings of Continuous Scientific Recording using Photography: Sir Francis Ronalds' Contribution". European Society for the History of Photography. Retrieved 2 June 2016. 
  5. ^ Keithley, Making precision low current and high resistance measurements, "A greater measure of confidence" brochure, 2011, page 8
  6. ^ Keithley, Nanovoltmeter 2182A, Datasheet, page 5
  7. ^ XL7900 Vibrating capacitor data sheet
  8. ^ CK5889 Electrometer pentode data sheet
  9. ^ Inverted Triode for Industrial Measurements, Manual of Industrial Circuits Electronics. Electronics. December 1944. p. 176. 

External links[edit]

Disclaimer

None of the audio/visual content is hosted on this site. All media is embedded from other sites such as GoogleVideo, Wikipedia, YouTube etc. Therefore, this site has no control over the copyright issues of the streaming media.

All issues concerning copyright violations should be aimed at the sites hosting the material. This site does not host any of the streaming media and the owner has not uploaded any of the material to the video hosting servers. Anyone can find the same content on Google Video or YouTube by themselves.

The owner of this site cannot know which documentaries are in public domain, which has been uploaded to e.g. YouTube by the owner and which has been uploaded without permission. The copyright owner must contact the source if he wants his material off the Internet completely.

Powered by YouTube
Wikipedia content is licensed under the GFDL and (CC) license