Abstract: The vitiating effect on the fluorescence measuring signal of extraneous currents flowing through the fluorescence detection means in flash spectrofluorimetry is almost completely eliminated by integrating the output of the fluorescence measuring means for the duration of the signal period, which includes a flash duration, and again for an equal period occurring between flashes which therefore does not include a flash duration. The second integral is then subtracted from the first to obtain a fluorescence measuring signal substantially unaffected by extraneous currents, such as dark current, sample phosphorescence, etc. The invention is applicable to single- and double-channel operation. In the latter, in addition to the fluorescence measuring channel there is provided a fluorescence reference channel. This enables the fluorescence measuring signal and the fluorescence reference signal to be ratioed together, the effect of extraneous currents having first been eliminated in both.

Abstract: Disclosed herein is method and apparatus for determining the nature of an unknown substance, which includes apparatus for entering a peak table of the spectrum of an unknown substance into computing apparatus, apparatus for adjusting the peak table to a first preselected standardized format, computing apparatus for comparing the so standardized peak table of the unknown with a first library of chemical structural units contained in memory in the computing apparatus, apparatus for making a list of the possible chemical structural units most closely corresponding to the unknown substance, apparatus for readjusting the peak table to a second preselected standardized format, apparatus for forming a file for the unknown substance including data corresponding to the readjusted peak table and to the list of possible chemical structural units, computing apparatus for comparing the file of the unknown substance with a second library containing files of known substances contained in memory in the computing apparatus, e

Abstract: A light chopper for chopping the monochromatic light beam of a spectrophotometer system, has a rotatable shaft driven by a synchronous motor at a frequency proportional to the power line frequency. An aperture bearing disc rotates with the shaft in relation to a photocell/detector array for generating digital timing signals for use by a microcomputer to control the tasks of the spectrophotometer system in synchronism with line frequency. The microcomputer monitors line frequency for responsively programming a programmable divider for generating an index signal for proportionally sequencing the wavelength of the monochromatic beam through a predetermined spectral range.

Abstract: A cross-talk balancing circuit for double-beam spectrophotometers is disclosed. The circuit includes means to measure in four successive sample periods the sample plus sample re-radiation (S + s), reference radiation plus reference re-radiation (R + r), sample re-radiation (s) and reference re-radiation (r). The detector, however, does not respond quickly so it introduces cross-talk into each measurement. Electronic phasing circuitry selects the time when the detector output is sampled so that the cross-talk in the measurements is equalized permitting it to be subtracted out of the measurement thereby leaving a remainder which accurately corresponds to the desired quantities S and R.

Abstract: In a plotting apparatus such as a spectrophotometer having a modifying system which introduces a phase lag between the occurrence of a change in a dependent variable quantity and plotting thereof against an independent variable quantity, in one embodiment, a cam is used to provide a quantity representing the dependent phase lag and the output of the cam is coupled to the driving system for the plotter so as to introduce therein a phase shift to compensate for the phase lag. In another, electrical embodiment the same object is accomplished by digitizing the phase lag and using the digital value to offset the wavenumber stepper motor and the chart stepper motor in the spectrophotometer with respect to each other.

Abstract: In a device such as a spectrophotometer with an associated chart recorder in which the speed ratio between a first displaceable member and a second displaceable member may be selectively changed within a predetermined range of speed ratios, in a first embodiment of invention which is mechanical in nature, a number of gear trains in constant mesh with each other are provided to obtain the different speed ratios. Each of the gear trains has associated therewith a rotary disc with circumferentially even spaced apertures, the gear train obtaining an input from the first displaceable member by means of arms rotatable concentric with the discs, the arms carrying a pin adapted to enter into positive engagement with any one aperture, the number apertures depending on the scale served by the associated gear train.