The Perkin-elmer Corporation

Morteza M Chamran

Larkin B Scott

Paul B Williams

Michael A Ford

Allen R Nemec

Milan R Dimovski

Milan Dimovski

A programmable timer controls the duration of integration with respect to time of an unknown analog signal in accordance with a programmable time period established by a microprocessor. A switching logic successively transfers an analog signal and a voltage reference signal to an integrator under logic control actuated by the programmable timer. A comparator monitors the value of the integration of the reference voltage in order to control the time-out results of an event counter initiated simultaneously with input to the integrator of the reference voltage, for providing a digital count output signal to the microprocessor.

Analog-to-digital converter having programmable dynamic range

A discharge lamp firing apparatus is disclosed which includes providing only the necessary firing voltage to the lamp prior to the firing thereof. As such, the surrounding system is not subjected to transients caused by conventional mechanisms which suddenly switch an extremely high voltage across the lamp. As a result, the present apparatus protects the associated circuitry as well as prevents needless overvoltage conditions to the lamp.

Lamp firing apparatus

A spectrophotometer system has an optical system for transmitting a beam from a source at select wavelengths onto a detector. A plurality of filters are positioned in a tray. A stepper mechanism indexes the tray along a path. A microcomputer controls the stepper mechanism and the optical system. The wavelength is successively changed over a range, the tray is indexed to move a select filter into the beam at a predetermined wavelength and the changing is discontinued during indexing.

Filter indexing for spectrophotometer system

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. The rotatable shaft is coupled to the synchronous motor via a mechanical pin drive and a set of attracting magnets which are spaced in face confronting relation at the point of coupling for providing compliance and damping between the coupled shaft and synchronous motor, thus minimizing phase jitter of the timing system and permitting rejection of time frequency stray circuit pickup.

Spectrophotometer system having power line synchronization

An improvement in a spectrophotometer of an improved apparatus for automatic initialization of the wavelength indexing function of the spectrophotometer. A drive mechanism drives the wavelength indexing movement of the spectrophotometer diffraction grating. The grating is initialized to a grating initialization position by physical opposition of a stop mechanism to the driving when a drive linkage reaches a drive linkage initialization position.

Spectrophotometer improvement of improved automatic wavelength indexing

A microprocessor based spectrophotometer including a memory system for providing storage locations of sets of operating parameters and correction data. The operator loads the memory via keyboard control. The memory system is battery backed-up for maintaining stored data during power shutdown of the spectrophotometer system.

Safe memory system for a spectrophotometer

A microprocessor based spectrophotometer including manual keyboard command for sequencing a monochromatic energy beam through a spectral range of wave-lengths to a keyboard selected wavelength. A manual adjustment knob is thereafter rotatable for generating a 4-bit gray code signal which successively changes as the adjustment knob is rotated. The microcomputer senses a change in the gray code signal and indexes (steps) the wavelength of the monochromatic beam in proportion to the positional change of the adjustment knob as indicated by the changing gray code. A visual display indicating wavelength setting and spectral response, is updated conjointly with manual wavelength adjustment.

Manual wavelength adjustment for a microprocessor based spectrophotometer

An improved photodetector arrangement comprises positioning a photodetector having at least one semi-transparent cathode so that the light beam striking the cathode passes through it at least twice before exiting from the photodetector. In another embodiment of the invention, a second photodetector is positioned relative to a first photodetector so that the light beam, after striking the first photodetector, strikes the second photodetector. Where the two photodetectors are employed, they may be electrically connected in parallel.

Photodetector arrangements and circuits

A circuit permitting an operator to accurately calibrate an instrument to indicate when a variable analog quantity being measured is zero. The analog signal is connected to the input of an operational amplifier which operates in stable mode for large analog inputs and operates in oscillation mode for very small analog inputs. The output of the operational amplifier is compared to zero and when the analog input is greater than zero, the comparator output is a logic zero. When the analog input is less than zero and not in the immediate vicinity of zero, the comparator output is a logic one. When the analog input is very small and less than zero, the operational amplifier operates in oscillation mode as the circuitry connected thereto causes it to oscillate with the duty cycle of the negative portion of the oscillation decreasing as the analog input comes closer to zero. Accordingly, the output of the comparator also oscillates. The comparator output connects to a sign driver of a typical seven segment display and the sign indication provided thereby grows dimmer as the analog input approaches zero from the negative direction.

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Elmhurst, IL, United States of America

Morteza M Chamran