Range selector switch for ion chamber instrument
US4977367A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jan 28, 1988 |
| Grant date | Dec 11, 1990 |
| Priority date | — |
| Expiry date | Jan 28, 2008 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01T1/185
- WIPO fieldEnvironmental technology
- WIPO sectorChemistry
Abstract
An ion chamber type instrument for measuring radioactivity includes a high gain operational amplifier having a feedback network of range determining resistors connected between the amplifier output and input. Electronic switches in series with at least some of the range determining resistors function as range selector switches for the measuring instrument. Each switch includes two series-connected transistors and a third transistor, the interconnection point between the two series-connected transistors being connected to the electrical neutral point of a measuring circuit via the third transistor. Each switch, when in an "off" or non-conducting condition, provides a high effective resistance of, for example, 1.times.10.sup.15 ohms so as to minimize errors caused by leakage current fed back into the input of the high gain operational amplifier.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.