Method and apparatus for measuring low currents in capacitance devices

Patent · Wed Jun 04 00:00:00 EDT 1986

OSTI ID:6533995

Kopp, M K; Manning, F W; Guerrant, G C

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.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• DOE Contract Number: AC05-84OR21400
• Assignee: Dept. of Energy
• Application Number: ON: DE87007185
• OSTI ID: 6533995
• Resource Relation: Other Information: Portions of this document are illegible in microfiche products
• Country of Publication: United States
• Language: English

Related Subjects

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