Abstract

Most applications of modern spectrophotometry demand that spectrophotometric measurements be recorded on media suitable for direct use by data processing equipment. This paper describes a photomechanical method for actuating the readout command for an old model GE recording spectrophotometer. This instrument has nonlinear wavelength representation in the near ultraviolet and near infrared. The method involves an opaque disk having a direct one-to-one rotation relation with the wavelength drive. The disk contains three sets of small holes on the circumference of concentric circles which represent the near ultraviolet, visible, and near infrared regions of the spectrum. The accurate angular separation of these holes, along with a photodiode and lamp which are aligned for each set of holes, makes available a selection of these three ranges and automatically actuates the readout command in the control chassis at 10-nm intervals for all wavelength ranges. The data are then punched into cards by an IBM 526 summary punch. The option of taking data at 5-nm intervals is provided by a suitable second disk.

© 1970 Optical Society of America

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References

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  1. A. Susskind, Notes on Analogue-to-Digital Conversion Techniques (MIT Press, Boston, 1957), Chap. 6.
  2. E. T. Powner, J. Sci. Instrum. 43, 454 (1966).
    [CrossRef] [PubMed]
  3. W. B. Prescott, H. C. Lawrence, U.S. Patent3,459,480, Official Gazette, 5Aug.1969, p. 168.
  4. Datex Corp., Monrovia, Calif.

1966 (1)

E. T. Powner, J. Sci. Instrum. 43, 454 (1966).
[CrossRef] [PubMed]

Lawrence, H. C.

W. B. Prescott, H. C. Lawrence, U.S. Patent3,459,480, Official Gazette, 5Aug.1969, p. 168.

Powner, E. T.

E. T. Powner, J. Sci. Instrum. 43, 454 (1966).
[CrossRef] [PubMed]

Prescott, W. B.

W. B. Prescott, H. C. Lawrence, U.S. Patent3,459,480, Official Gazette, 5Aug.1969, p. 168.

Susskind, A.

A. Susskind, Notes on Analogue-to-Digital Conversion Techniques (MIT Press, Boston, 1957), Chap. 6.

J. Sci. Instrum. (1)

E. T. Powner, J. Sci. Instrum. 43, 454 (1966).
[CrossRef] [PubMed]

Other (3)

W. B. Prescott, H. C. Lawrence, U.S. Patent3,459,480, Official Gazette, 5Aug.1969, p. 168.

Datex Corp., Monrovia, Calif.

A. Susskind, Notes on Analogue-to-Digital Conversion Techniques (MIT Press, Boston, 1957), Chap. 6.

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Figures (12)

Fig. 1
Fig. 1

datex shaft encoder, shown on the left, mounted on the photometric cam of a GE spectrophotometer.

Fig. 2
Fig. 2

Schematic of a datex C-127B shaft encoder with table showing brush positions and corresponding output to control chassis.

Fig. 3
Fig. 3

The commutator assembly for triggering digital data on a Cary Model 14 spectrophotometer.

Fig. 4
Fig. 4

Mechanical gear-driven cam for closing the microswitches in the triggering circuit for digital output on a GE spectrophotometer.

Fig. 5
Fig. 5

Opaque disk with holes, on left, for modulating the light falling on the photodetectors. Mask for digitizing at 10-nm intervals on right.

Fig. 6
Fig. 6

Circuit diagram for power supply and triggering of datex control chassis. Circuit components: T1, Rittenhouse ST-187 step-down transformer; FWR, Ledex A-46502-03 full wave rectifier; C, 300-μF,12-V electrolytic capacitor; R, 39-Ω,½-W resistor; D1, 1N3020B Zener diode; PD, LS 400 photodiodes—Texas Instrum. Co.; L, GE 328 6-V lamps; SW1, Centralab ceramic rotary switch; MR, Potter and Brumfield relay JML-1190-81.

Fig. 7
Fig. 7

Mask position for digitizing at 5-nm intervals.

Fig. 8
Fig. 8

Mask position for digitizing at 10-nm intervals.

Fig. 9
Fig. 9

Photograph of the system showing the disk modulator, mask, lamp positions, datex encoder, and analog cam shaft.

Fig. 10
Fig. 10

Spectrophotometric curves of a turbid medium: upper curve, percent transmittance; lower curve, percent reflectance.

Fig. 11
Fig. 11

Calcomp plot of absorptance vs wavelength computed from digitized data taken with turbid medium (see Fig. 10).

Fig. 12
Fig. 12

The computer-plotted spectrophotometric curve of a yellow sample after mathematical treatment of the original data.

Tables (1)

Tables Icon

Table I Parameters Computed for Spectral Density Distribution of Fig. 12

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