GB681214A - Improvements in or relating to apparatus for measuring small currents or voltages - Google Patents
Improvements in or relating to apparatus for measuring small currents or voltagesInfo
- Publication number
- GB681214A GB681214A GB851550A GB851550A GB681214A GB 681214 A GB681214 A GB 681214A GB 851550 A GB851550 A GB 851550A GB 851550 A GB851550 A GB 851550A GB 681214 A GB681214 A GB 681214A
- Authority
- GB
- United Kingdom
- Prior art keywords
- capacitor
- coils
- plate
- movable element
- coil
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/18—Arrangements for measuring currents or voltages or for indicating presence or sign thereof using conversion of DC into AC, e.g. with choppers
Abstract
681,214. Current and voltage measurements; electric condensers. COLE, Ltd., E. K., and FINCH, H. W. S. April 5, 1951 [April 5, 1950], No. 8515/50. Class 37. In a dynamic electrometer of the type in which a capacitor, whose capacitance is made to vary cyclically by a fluctuating driving E.M.F., is employed to convert an applied D.C. potential to an A.C. potential, the natural frequency of vibration of the movable element of the capacitor is used as the frequencydetermining element of the system, so as to ensure that the frequency of the driving E.M.F. always bears a constant relationship to the natural frequency of vibration. A capacitor 1, Fig. 1, having a movable element, such as a vibrating reed of magnetic material, is connected across leads a to which the unidirectional voltage or current to be measured is applied. The circuit comprises a resistance R<SP>1</SP> and a highly insulated condenser C<SP>1</SP>, the fluctuations across which are impressed on an A.C. amplifier 2, the output of which is applied to a phasesensitive detector 3. The movable element of the capacitor 1 is energized by the coils L in a thermionic valve circuit 4. This serves as a standard-wave generator whose frequency is determined by the natural frequency of vibration of the movable element of the capacitor 1. A connection is taken from the generator 4 to the detector 3 for comparison with the output from the amplifier 2. The output from the detector 3 is fed to a cathode follower 5 whose output is measured by a voltmeter V. A negative feed-back circuit 6 ensures that variations in the gain of the amplifier &c. have minimum effect on the readings, so that the instrument is suitable as a null detector. A suitable construction of vibrating-reed capacitor is shown in Fig. 2. One plate M of the capacitor is mounted on a polystyrene block U and is fitted with a screwed shank W to permit adjustment of the gap. The movable element is a stainless steel reed O<SP>1</SP> vibrated by an electromagnet P which is energized by the coils L, Fig. 1, and is provided with a screen S. One end of the reed O<SP>1</SP> is fixed to the casing at T. The condenser C<SP>1</SP>, Fig. 1, is made integral with the assembly of the fixed plate M and is of moulded construction, having a polythene dielectric and possessing high insulation resistance. In the construction shown in Fig. 3, a circular permanent magnet, N, with concentric polepieces, carries one of the coils L wound on an insulating former fixed around the central polepiece. The other coil is wound on a cylindrical former Q suspended at T by an internal diaphragm and constrained so that the coil is free to move only in the central plane of the central polepiece. The former Q also carries a metal plate O<SP>2</SP> which forms the movable plate of the capacitor. The fixed plate M is fitted with a screwed shank W and is carried by an insulating support U which is rigidly connected to the magnet N by means not shown. The coils L are connected in a thermionic valve circuit as shown in Fig. 5. An alternating voltage is generated in the coils so that the suspended coil is alternately attracted to and repelled from the fixed coil and imparts oscillatory motion to the plate O<SP>2</SP>. In the construction shown in Fig. 4, a non-magnetic casing R encloses a permanent magnet V on which are mounted the coils L. Over the top of the polepieces is a tightly stretched diaphragm Y of magnetic material which may form the movable plate of the capacitor or, as shown, may be mechanically coupled to a separate plate O<SP>3</SP>. Specification 550,610 is referred to.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB851550A GB681214A (en) | 1950-04-05 | 1950-04-05 | Improvements in or relating to apparatus for measuring small currents or voltages |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB851550A GB681214A (en) | 1950-04-05 | 1950-04-05 | Improvements in or relating to apparatus for measuring small currents or voltages |
Publications (1)
Publication Number | Publication Date |
---|---|
GB681214A true GB681214A (en) | 1952-10-22 |
Family
ID=9853926
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB851550A Expired GB681214A (en) | 1950-04-05 | 1950-04-05 | Improvements in or relating to apparatus for measuring small currents or voltages |
Country Status (1)
Country | Link |
---|---|
GB (1) | GB681214A (en) |
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2989701A (en) * | 1957-11-26 | 1961-06-20 | Hagan Chemicals & Controls Inc | Monitoring equipment |
DE1121219B (en) * | 1958-01-02 | 1962-01-04 | Siemens Ag | Oscillating capacitor |
DE1141336B (en) * | 1958-08-27 | 1962-12-20 | Laszlo Natonek | Arrangement for keeping constant the oscillation amplitudes of an oscillation capacitor for DC voltage amplifiers |
US3090916A (en) * | 1961-05-26 | 1963-05-21 | Hagan Chemicals & Controls Inc | Multiple range measuring system for non-linear input signals using feedback gain control means to provide a linear response |
DE3015859A1 (en) * | 1979-04-24 | 1980-11-06 | Canon Kk | SURFACE POTENTIAL ELECTROMETER AND IMAGING DEVICE EQUIPPED WITH THIS |
CN110308472A (en) * | 2019-06-06 | 2019-10-08 | 中国工程物理研究院核物理与化学研究所 | A kind of dynamic condenser for D.C.current modulation |
-
1950
- 1950-04-05 GB GB851550A patent/GB681214A/en not_active Expired
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2989701A (en) * | 1957-11-26 | 1961-06-20 | Hagan Chemicals & Controls Inc | Monitoring equipment |
DE1121219B (en) * | 1958-01-02 | 1962-01-04 | Siemens Ag | Oscillating capacitor |
DE1141336B (en) * | 1958-08-27 | 1962-12-20 | Laszlo Natonek | Arrangement for keeping constant the oscillation amplitudes of an oscillation capacitor for DC voltage amplifiers |
US3090916A (en) * | 1961-05-26 | 1963-05-21 | Hagan Chemicals & Controls Inc | Multiple range measuring system for non-linear input signals using feedback gain control means to provide a linear response |
DE3015859A1 (en) * | 1979-04-24 | 1980-11-06 | Canon Kk | SURFACE POTENTIAL ELECTROMETER AND IMAGING DEVICE EQUIPPED WITH THIS |
CN110308472A (en) * | 2019-06-06 | 2019-10-08 | 中国工程物理研究院核物理与化学研究所 | A kind of dynamic condenser for D.C.current modulation |
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