Method and apparatus for measuring low currents in capacitance devices
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 Lab., TN (USA)
- DOE Contract Number:
- AC05-84OR21400
- Assignee:
- Dept. of Energy
- Patent Number(s):
- None
- Application Number:
- ON: DE87007185
- OSTI ID:
- 6533995
- Country of Publication:
- United States
- Language:
- English
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Capacitance measuring device
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Related Subjects
420800* -- Engineering-- Electronic Circuits & Devices-- (-1989)
440102 -- Radiation Instrumentation-- Radiation Dosemeters
440300 -- Miscellaneous Instruments-- (-1989)
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
47 OTHER INSTRUMENTATION
AMMETERS
AMPLIFICATION
CAPACITORS
CURRENTS
DESIGN
DOSE RATEMETERS
ELECTRIC CURRENTS
ELECTRIC MEASURING INSTRUMENTS
ELECTRICAL EQUIPMENT
EQUIPMENT
GAIN
IONIZATION CHAMBERS
MEASURING INSTRUMENTS
RADIATION DETECTORS