Method and apparatus for comparing the transmittance of a sample and a standard
Abstract
Abstract A TRANSMITTANCE TO FREQUENCY CONVERTER WHERE A COMMON LIGHT SOURCE ILLUMINATES A SAMPLE CUVETTE AND A REFERENCE CUVETTE. THE TRANSMITTED LIGHT IS INDIVIDUALLY MEASURED BY TWO PHOTOTUBES. THE TIME AVERAGE OUTPUT CURRENTS OF THE TWO PHOTOTUBES ARE OF OPPOSITE POLARITIES AND ARE COMBINED IN AN INTEGRATING CAPACITOR COUPLED TO A COMPARATOR. THE COMPARATOR IS PART OF FEEDBACK CONTROL LOOP WHICH PROVIDES FOR CONTROL OF THE TIME AVERAGE OF THE REFERENCE CURRENT TO MAKE IT EQUAL TO THE AVERAGE SAMPLE CURRENT. A TRANSISTOR SWITCH CONTROLS THE "ON" TIME OF THE REFERENCE PHOTOTUBE TO THEREBY CONTROL OF THE TIME AVERAGE OF THE REFEENCE CURRENT. THE DUTY CYCLE OF THE SWITCH IS PROPORTIONAL TO THE TRANSMITTANCE OF THE SAMPLE.
Inventors
- 👤 Douglas H Smith
Bibliographic Details
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