Light meter
US4218140A · kind A · utility
4Cited by
3References
15Claims
0Family size
Assignee
Inventors
Key dates
| Filing date | Aug 21, 1978 |
| Grant date | Aug 19, 1980 |
| Priority date | — |
| Expiry date | Aug 21, 1998 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03F2200/372
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
To permit a portable light meter to operate without zero adjustment and without excessive battery drain, a chopper-stabilized amplifier amplifies the DC signal from the light sensor of the light meter. The chopper in the chopper-stabilized amplifier is an FET circuit having a high impedance compensating circuit to avoid battery drain while compensating for interelectrode capacitance. The power supply obtains the ground level potential from the output of an operational amplifier with negative and positive potentials being generated from that reference potential so as to not require a center tap on the battery pack.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.