Abstract

The instrument consists of a vacuum photoelectric cell feeding into a vacuum tube voltmeter with logarithmic input characteristic. The voltmeter employs a type 6D6 tube which is provided with a properly chosen biasing resistor in the cathode lead. This gives a plate current proportional to the logarithm of the input voltage. Since this relationship never extends to zero plate current, a portion of the plate current is balanced out, giving in effect, a suppressed zero instrument. Suitable shunts and a choice of input resistors afford several ranges of sensitivity. The output meter can be calibrated directly in concentration units. Other methods of achieving the same result are discussed.

© 1935 Optical Society of America

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References

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  1. R. H. Müller, Mikrochemie 11, 353 (1932);Ind. Eng. Chem. Anal. Ed. 7, 223 (1935).
    [CrossRef]
  2. S. Ballentine, Electronics 2, 472 (1931);J. Acous. Soc. Am. 5, 10 (1933);F. V. Hunt, R. S. I. 4, 672 (1934).
    [CrossRef]

1932 (1)

R. H. Müller, Mikrochemie 11, 353 (1932);Ind. Eng. Chem. Anal. Ed. 7, 223 (1935).
[CrossRef]

1931 (1)

S. Ballentine, Electronics 2, 472 (1931);J. Acous. Soc. Am. 5, 10 (1933);F. V. Hunt, R. S. I. 4, 672 (1934).
[CrossRef]

Ballentine, S.

S. Ballentine, Electronics 2, 472 (1931);J. Acous. Soc. Am. 5, 10 (1933);F. V. Hunt, R. S. I. 4, 672 (1934).
[CrossRef]

Müller, R. H.

R. H. Müller, Mikrochemie 11, 353 (1932);Ind. Eng. Chem. Anal. Ed. 7, 223 (1935).
[CrossRef]

Electronics (1)

S. Ballentine, Electronics 2, 472 (1931);J. Acous. Soc. Am. 5, 10 (1933);F. V. Hunt, R. S. I. 4, 672 (1934).
[CrossRef]

Mikrochemie (1)

R. H. Müller, Mikrochemie 11, 353 (1932);Ind. Eng. Chem. Anal. Ed. 7, 223 (1935).
[CrossRef]

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Figures (8)

F. 1
F. 1

Modes of representing colorimetric data.

F. 2
F. 2

Plate current-grid potential values as a function of cathode resistance. A = 0Ω, B = 1800Ω, C = 2500Ω, D = 5000Ω, E =10,000Ω.

F. 3
F. 3

Circuit for logarithmic photoelectric colorimeter.

F. 4
F. 4

Mechanical disposition of parts in completed colorimeter.

F. 5
F. 5

Photoelectric measurements with copper solutions, illustrating logarithmic (direct reading) response.

F. 6
F. 6

Logarithmic response of Weston Photronic cell.

F. 7
F. 7

Circuit for logarithmic colorimeter employing a Photronic cell.

F. 8
F. 8

Photoelectric measurements with copper solutions, using circuit shown in Fig. 7.

Tables (1)

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Table I

Equations (2)

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I = I 0 e k c t ,
log ( I 0 / I ) = k c .