Keying waveform generator for spectrophotometer
US4030829A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Apr 12, 1976 |
| Grant date | Jun 21, 1977 |
| Priority date | — |
| Expiry date | Apr 12, 1996 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01J3/42
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
In a double beam spectrophotometer employing a rotating optical chopper to direct a beam of electromagnetic radiation alternately through sample and reference channels to a photomultiplier tube, a beam interrupter is used in combination with a photodiode and a photocell to generate a square wave signal having a predetermined temporal relation to the rotation of the optical chopper. The square wave signal is integrated to provide a triangular waveform, whose maxima and minima correspond, respectively, to the passage of the beam through one or the other of the sample and reference channels, and whose cross-over points with respect to a zero reference level correspond to dark intervals during which the beam is blocked from entering either channel. Keying circuitry responsive to the cross-over points provides for detection of dark current generated by the photomultiplier tube, while keying circuitry responsive to the maxima and minima synchronizes analysis circuitry associated with the sample and reference channels with the passing of the beam therethrough and provides for correction of the output of the photomultiplier tube to compensate for dark current.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.