The Perkin-elmer Corporation

Perkin-elmer Corporaton

Larkin B Scott

Morteza M Chamran

Paul B Williams

Michael A Ford

John J Staunton

William C Muellner

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 direct current servo motor operates through a toothed belt linkage to drive the pen carriage of a chart recorder. The position of the drive is monitored by a sectored encoder disc on the motor shaft. A pair of optical sensors is located relative to the encoder disc to provide alternately phased transition signals as corresponding edges of the encoder disc sectors pass the sensors when the motor rotates. A microprocessor interrupted by a transition signal goes to a sub-routine that determines which way the encoder disc is rotating and stores a count signal of the corresponding sign in a register. Further the microprocessor compares an input signal with the stored count signal and directs the motor to rotate in the direction that will reduce the difference or error signal to zero thus causing the pen to follow the magnitude of the input signal. The sub-routine also computes the rate of error change and applies a correction to motor speed or brakes the motor when the error approaches zero to prevent pen overshoot.

Pen drive for recorder

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

The disclosed high resolution analog to digital converter circuit has an integrator circuit responsive to the unknown analog input. The integrator circuit is operated for a fixed period of time during which, on a periodic basis, a predetermined charge is dumped from the integrator circuit capacitor. A counter is incremented each time a dump occurs and the counter value at the end of the fixed period is related to the high order digits of the digital value for the unknown analog signal. A digital number corresponding to the output level of the integrator is determined by a successive approximation circuit both before and just after the fixed period. The difference between the two values determined by the successive approximation circuit is related to the low order digits of the digital value for the unknown analog signal.

High resolution analog to digital converter

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

In a device in which an independent variable is stepped or scanned between a first limit and second limit and in which device there is an error which is a function of the independent variable, error correction is obtained by storing correction values, preferably of an incremental nature, for each of a plurality of steps of the independent variable, establishing a location marker which can be identified as different from the error correction data, moving the location marker so as to always be adjacent the error correction for the current position or step of the independent variable and reading out the error correction at the point of the location marker.

Method and apparatus for error correction

In an error correcting system in which error corrections for each of a plurality of steps of an independent variable in a device which has an error dependent upon the independent variable are stored in a register in adjacent storage positions thereof and wherein a location marker differing from any stored correction value is also stored in the register and moved as said device steps so as to always be adjacent the correction corresponding to the step of the device, the correction values being stored for a range of the device between a first limit and a second limit, the device having a greater overall range than the range between said first and second limit and being able to go to a position below said first limit, loss of synchronization between the device and the location marker when the device is moved below said first limit is prevented by detecting when said location marker reaches said first limit and causing it to move in a direction from said first limit toward said second limit as said device is moved below said first limit and in a direction toward said first limit as said device is moved from below said first limit back toward said first limit and again reversing the direction of movement of said location marker when said first limit is again reached with said independent variable moving in a direction toward said second limit permitting synchronization to be maintained even when going below the range for which correction values are stored.

System for maintaining below range synchronization in error correcting

Where the unknown leg of a bridge is a sensor which presents a resistance that relates to a parameter by a second order polynomial, a negative feedback circuit from the conventional null measurement terminals to a voltage divided point in the balance leg thereof is included to provide a substantially linear relationship between the parameter of the sensor and a ratio including two voltage levels from the feedback circuit. A circuit means for continuously monitoring this ratio of voltages with a counter in recurring cycles for digital display is incorporated with the linearized bridge circuit of this invention in a particular embodiment thereof.

Linearized bridge circuitry

An analytically significant ratio between timevarying magnitudes of signals is periodically monitored in recurring cycles which are each synchronized with a frequency generator. During every monitoring cycle, each signal relating to the numerator and denominator of the ratio, is integrated separately for a fixed number of generator cycles. Thereafter in each monitoring cycle, the output from the integrator of the denominator signal is applied at the input to the integrator of the numerator signal and the time taken by the latter to integrate back to its starting level is measured in proportion to the ratio of the signals. Either digital or analog time measurements may be utilized and the number of generator cycles over which the ratio is determined may include transition periods between each stage of integration.

Growing community of inventors

Fort Worth, TX, United States of America

Larkin B Scott