Abstract: A self-contained automatic computer controlled system for checking and recalibrating the wavelength scale of both monochromators of a fluorescence spectrophotometer is described. No operator adjustments are required. The system sets the wavelength of each monochromator to within 0.1 nanometers. Besides automatic indexing at turn-on the operation can be repeated at any desired time. The system is applicable to single or double monochromator instruments.

Abstract: The effective range of an analog linear-log converter is extended above the number of output decades over which this converter is reasonably linear to cover several additional decades of log conversion. This is made possible by adding a variable gain amplifier having several decades of switchable gain to the input of the converter. Switching between decades to utilize the added decades of output is controlled by a microcomputer which monitors the output level. This switching restores the signal level of each of the added decades to the same level as that of an earlier decade thus maintaining the same slope accuracy and noise levels of the earlier decades throughout the whole conversion range. The microcomputer also provides slope corrections from a lookup table for each of the different output decades as well as also applying to the output corrections for offsets due to the circuit components. Ambient temperature compensation is also provided following the linear-log converter for increased precision.

Abstract: A software controlled automatic shutter is described which minimizes ultraviolet irradiation damage to optical components from a high intensity spectrophotometric light source. The shutter automatically opens when measurements are being made and closes when the photometer system is idle. The digital control system may be self contained so as to avoid complication of the main computer.

Abstract: It has been shown that the use of a shutter to cut off the light beam entering the optical system of a fluoresence spectrophotometer will reduce UV deterioration of the components in the optical system. This invention discloses how control of the output of the light source by lowering its arc current when the shutter is closed can add significant improvement to the functioning of such a shutter system.

Abstract: A timing system for a spectrophotometer having a line driven chopper including a rotating disc with alternate open and opaque segments, index apertures in the disc spaced at invariant angular relationship to one of the open segments for providing indexing pulses having fixed time relationship to the light segments, and a programmable microcomputer assembly for generating a string of timing pulses for timing spectrophotometer operations and adjusting the rate of the timing pulses to provide a fixed number between indexing pulses in fixed phase relationship thereto.

Abstract: In a spectrophotometer having an optical beam chopped into dark and light segments, a computer controlled system is described for determining background signal due to stray light, photomultiplier dark current, offsets of photometric amplifiers and other components, and the like and for subtracting this background signal from the overall signal so as to leave only the desired light measurement. The same computer system also sets the signal level automatically for highest resolution. Furthermore, the same computer acts as an analog to digital converter by successive approximation to supply the photometric signal to the microprocessor unit. Since the same components are involved in all these functions both analog and digital offsets of the components are automatically cancelled.