Optics: measuring and testing – By dispersed light spectroscopy – Utilizing a spectrophotometer
Patent
1980-02-27
1981-12-15
Evans, F. L.
Optics: measuring and testing
By dispersed light spectroscopy
Utilizing a spectrophotometer
G01J 308, G01J 342
Patent
active
043056636
ABSTRACT:
A dual beam spectrophotometer includes a radiation chopper, a monochrometer, and a diffraction grating moved by a stepper motor. The chopper includes a gate pulse generator which produces gate pulses G.sub.S and G.sub.R corresponding to periods during which radiation from the source passes through a sample cell and a reference cell respectively. A stepper motor drive circuit produces pulses to step the stepper motor which are synchronized with the chopping cycle by means of the G.sub.R and G.sub.S pulses. The stepper motor is arranged to step an equal number of times in each half of a chopping cycle. A further condition which is preferably satisfied is that the first pulse of a sequence should start in the opposite half of the chopping cycle from that in which the first pulse started in a previous chopping cycle. At low stepping rates the motor will step twice in one chopping cycle and then pause for several cycles before again stepping twice.
REFERENCES:
patent: 3563656 (1971-02-01), Helms
patent: 3843259 (1974-10-01), Tohyama et al.
patent: 4171913 (1979-10-01), Wildy et al.
Firth John R.
Perkins Charles V.
Briody Thomas A.
Evans F. L.
Mayer Robert T.
Miller Paul R.
PYE (Electronic Products) Limited
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