Control apparatus for spectrophotometer

• US 4,293,222 A
• Filed: 02/09/1979
• Issued: 10/06/1981
• Est. Priority Date: 02/27/1978
• Status: Expired due to Term

• Current Assignee: SLM Instruments Incorporated (Trane Technologies plc)
• Original Assignee: Baxter Travenol Laboratories Incorporated (Baxter International Inc.)
• Inventors: Dighe, Kamalakar D., Caruso, Stephen
• Primary Examiner(s): McGraw, Vincent P.
• Application Number:
  US06/010,734
• Time in Patent Office: 970 Days
• Field of Search: 356/319-325, 356/326
• US Class Current: 356/319
• CPC Class Codes: G01J 3/42 Absorption spectrometry; Double beam spectrometry; Flicker spectrometry; Reflection spectrometry beam switching arrangements G01J3/08

Abstract

The control apparatus is used with a dual beam spectrophotometer in which light of variable frequency from a light source is split into two beams which are directed along first and second optical paths to a photosensitive device. The control apparatus comprises electric control, processing and memory circuits coupled to the spectrophotometer for receiving and storing signals therefrom such as an output signal indicative of the particular wavelength of the light beams at any point in time and a log difference signal indicative of absorbance. The circuits include a first memory and a second memory for receiving and storing the log difference signals and control and processing circuitry for manipulating the data stored in the memory circuits. A wavelength digital display, an absorbance digital display and a CRT are provided. The control and processing circuitry causes a graph of wavelength v. absorbance to be traced on the CRT corresponding to absorbance data stored in the one memory for a particular wavelength span. A control circuit is coupled to the one memory for causing a cursor operation on the trace. The cursor is seen as an intensified dot on the trace and the control circuit includes a switch and stepping circuitry for moving the dot along the trace in increments as the particular wavelength and absorbance values corresponding to the dot are shown on the wavelength and absorbance displays. The cursor operation is also performed by moving a pen of a recorder in increments on a plotted curve.

Claims

1. A control apparatus for use with a dual beam spectrophotometer of the type in which light from a light source is split into two beams which are directed along respective first and second optical paths to a photosensitive device, the first optical path passing through a reference station and the second optical path passing through a sample station, and of the type which includes means for changing the wavelength of the light from a light source over a predetermined time period through a span of at least 75 nanometers and up to 600 nanometers or some segment thereof, starting at a wavelength of 200 nanometers or greater and proceeding up to a wavelength of 825 nanometers or less, means associated with the wavelength changing means for producing an output signal indicative of a particular wavelength of the light beams at any point in time and signal generating means coupled to the photosensitive device for subtracting the log of each signal generated by the light received by the photosensitive device from the second optical path from the log of each signal generated by light received by the photosensitive device from the first optical path and then producing a log difference signal indicative of absorbance, said control apparatus comprising electric circuit means including control, processing and memory circuits adapted to be coupled to the spectrophotometer for receiving and storing signals therefrom, said electric circuit means including first memory circuit means and second memory circuit means for receiving and storing the varying log difference signals, control and processing means for manipulating the data comprised of signal values stored in said memory circuit means, said manipulations including transferring data in one memory circuit means to the other memory circuit means, adding data from one to the data of the other, subtracting data in one from data in the other and taking the derivative of data stored in one of the memory circuit means, wavelength digital display means, absorbance digital display means, and said control and processing circuit means being coupled to a recorder in the spectrophotometer and being operable to cause movement of a pen of the recorder to plot a spectrum of wavelength v. absorbance on the recorder from a spectrum of varying log difference signals which are related to absorbance and which are stored in said one of said memory circuit means, and said control and processing means including control means coupled to said one of said memory circuit means for causing a cursor operation on the curve plotted on the recorder, said cursor being seen as a holding of the pen at a particular point on the curve and said control and processing means being operable to cause a display on said respective wavelength and absorbance digital display means of the wavelength and absorbance at the particular position of the pen on the curve plotted on the recorder and said control means including means for moving said pen in increments along the curve plotted on the recorder.

2. A control apparatus for use with a dual beam spectrophotometer of the type in which light from a light source is split into two beams which are directed along respective first and second optical paths to a photosensitive device, the first optical path passing through a reference station and the second optical path passing through a sample station, and of the type which includes means for changing the wavelength of the light from a light source over a predetermined time period through a span of at least 75 nanometers and up to 600 nanometers or some segment thereof, starting at a wavelength of 200 nanometers or greater and proceeding up to a wavelength of 825 nanometers or less, means associated with the wavelength changing means for producing an output signal indicative of a particular wavelength of the light beams at any point in time and signal generating means coupled to the photosensitive device for subtracting the log of each signal generated by the light received by the photosensitive device from the second optical path from the log of each signal generated by light received by the photosensitive device from the first optical path and then producing a log difference signal indicative of absorbance, said control apparatus comprising electric circuit means including control, processing and memory circuits adapted to be coupled to the spectrophotometer for receiving and storing signals therefrom, said electric circuit means including first memory circuit means and second memory circuit means for receiving and storing the varying log difference signals, control and processing means for manipulating the data comprised of signal values stored in said memory circuit means, said manipulations including transferring data in one memory circuit means to the other memory circuit means, adding data from one of the data of the other, subtracting data in one from data in the other and taking the derivative of data stored in one of the memory circuit means, wavelength digital display means, absorbance digital display means, and visual display means coupled to one of said memory circuits, said control and processing means being operable to cause a graph of wavelength v. absorbance to be traced and displayed on said visual display means, such graph representing the signal values corresponding to absorbance stored in said one of said memory circuit means for a particular wavelength span and said control and processing means including control means coupled to said one of said memory circuit means for causing a cursor operation on the graph shown on the visual display device, said cursor operation being seen as an intensified dot on the waveform shown on the visual display device and said control means including means for moving said dot along said waveform in increments and for causing the particular wavelength and absorbance values at the point on the graph where the dot is located to be shown on said respective wavelength and absorbance digital display means.

3. The data modifying apparatus according to claim 2 wherein said control and processing means includes a central processing unit coupled to said first and second memory circuit means which are random access memory circuits, a read only memory circuit coupled through address circuitry to said contral processing unit, selection logic circuitry coupled to said central processing unit and having pulse inputs and an interrupt input, data distribution logic circuitry coupled to said central processing unit and to a Y-axis absorbance control output and to an X-axis wavelength control output, an X counter serially coupled to and between said data distribution logic circuitry and said X-axis wavelength control output, and cursor control means including a manually operated cursor increment upscale-downscale switch, a cursor generator coupled to said cursor increment switch and having outputs coupled to said pulse inputs of said selection logic circuitry, a cursor counter having inputs coupled to said outputs of said cursor signal generator and comparing means coupled to the outputs of said X counter and the outputs of said cursor counter for comparing the counts therein and having an output coupled to said interrupt input of said selection logic circuitry, said cursor control means being operable upon operation of said cursor increment switch to compare counts in said counters and upon coincicense, to send an interrupt signal to said interrupt input of said selection logic to cause updating in buffers in said random access memory circuits of (a) the cursor count of wavelength increments, (b) the wavelength at that particular count of wavelength increments, and (c) the corresponding absorbance value, movement of the electron beam of the oscilloscope being held while such updating takes place causing an intensified spot to develop on the screen of the oscilloscope to create the cursor dot.