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Title: Method and apparatus for measuring low currents in capacitance devices

Abstract

A method and apparatus for measuring subnanoampere currents in capacitance devices is reported. The method is based on a comparison of the voltages developed across the capacitance device with that of a reference capacitor in which the current is adjusted by means of a variable current source to produce a stable voltage difference. The current varying means of the variable current source is calibrated to provide a read out of the measured current. Current gain may be provided by using a reference capacitor which is larger than the device capacitance with a corresponding increase in current supplied through the reference capacitor. The gain is then the ratio of the reference capacitance to the device capacitance. In one illustrated embodiment, the invention makes possible a new type of ionizing radiation dose-rate monitor where dose-rate is measured by discharging a reference capacitor with a variable current source at the same rate that radiation is discharging an ionization chamber. The invention eliminates high-megohm resistors and low current ammeters used in low-current measuring instruments.

Inventors:
; ;
Issue Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
OSTI Identifier:
6533995
Application Number:
ON: DE87007185
Assignee:
Dept. of Energy
DOE Contract Number:  
AC05-84OR21400
Resource Type:
Patent
Resource Relation:
Other Information: Portions of this document are illegible in microfiche products
Country of Publication:
United States
Language:
English
Subject:
42 ENGINEERING; 47 OTHER INSTRUMENTATION; 46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; AMMETERS; DESIGN; CAPACITORS; DOSE RATEMETERS; ELECTRIC CURRENTS; GAIN; IONIZATION CHAMBERS; AMPLIFICATION; CURRENTS; ELECTRIC MEASURING INSTRUMENTS; ELECTRICAL EQUIPMENT; EQUIPMENT; MEASURING INSTRUMENTS; RADIATION DETECTORS; 420800* - Engineering- Electronic Circuits & Devices- (-1989); 440300 - Miscellaneous Instruments- (-1989); 440102 - Radiation Instrumentation- Radiation Dosemeters

Citation Formats

Kopp, M K, Manning, F W, and Guerrant, G C. Method and apparatus for measuring low currents in capacitance devices. United States: N. p., 1986. Web.
Kopp, M K, Manning, F W, & Guerrant, G C. Method and apparatus for measuring low currents in capacitance devices. United States.
Kopp, M K, Manning, F W, and Guerrant, G C. Wed . "Method and apparatus for measuring low currents in capacitance devices". United States.
@article{osti_6533995,
title = {Method and apparatus for measuring low currents in capacitance devices},
author = {Kopp, M K and Manning, F W and Guerrant, G C},
abstractNote = {A method and apparatus for measuring subnanoampere currents in capacitance devices is reported. The method is based on a comparison of the voltages developed across the capacitance device with that of a reference capacitor in which the current is adjusted by means of a variable current source to produce a stable voltage difference. The current varying means of the variable current source is calibrated to provide a read out of the measured current. Current gain may be provided by using a reference capacitor which is larger than the device capacitance with a corresponding increase in current supplied through the reference capacitor. The gain is then the ratio of the reference capacitance to the device capacitance. In one illustrated embodiment, the invention makes possible a new type of ionizing radiation dose-rate monitor where dose-rate is measured by discharging a reference capacitor with a variable current source at the same rate that radiation is discharging an ionization chamber. The invention eliminates high-megohm resistors and low current ammeters used in low-current measuring instruments.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {1986},
month = {6}
}