Photomultiplier tube circuit employing varistor

Claim 2

Circuit apparatus comprising: a. means for producing a signal which varies logarithmically with a certain parameter; b. means adapted to receive and exponentially amplify said signal to produce a signal that varies approximately linearly with said parameter; and c. varistor means across which said exponentially amplified signal is developed for adjusting said exponentially amplified signal to vary substantially linearly as a function of said parameter.

Claim 3

The circuit apparatus of claim 1 wherein said means adapted to receive and exponentially amplify said signal is a photomultiplier tube.

Claim 4

The circuit apparatus of claim 2 wherein said certain parameter is optical density, and wherein said means for producing a logarithmically variable signal includes a source of radiation and means having a sample density adapted to pass said radiation to said photomultiplier tube.

Claim 5

In combination with a photomultiplier tube circuit of the type adapted to amplify exponentially signals applied thereto and means for applying radiation to the input of the photomultiplier tube thereof, which radiation varies as a logarithmic function of a certain parameter; a varistor responsive to the output of said photomultiplier tube for adjusting said output to develop across itself a voltage which varies as a linear function of said parameter.

Claim 6

In combination with a photomultiplier tube circuit of the type adapted to amplify exponentially signals applied thereto and means for applying radiation to the input of the photomultiplier tube thereof, which radiation varies as a logarithmic function of a certain parameter; a varistor responsive to the output of said photomultiplier tube for adjusting said output to develop across itself a voltage which varies as a linear function of said parameter.

Claim 7

The circuit of claim 4 wherein said means for applying radiation includes a source thereof and sample means, having an optical density, for receiving and passing said source radiation to the input of said photomultiplier tube, whereby said varistor produces a voltage thereacross which is representative of the optical density of said sample means.

Claim 8

In combination with a radiation responsive photomultiplier tube: a. voltage divider means for application of potentials to the dynodes of the photomultiplier tube; b. variable impedance means in series with the voltage divider means responsive to the current flow through said photomultiplier tube to vary the impedance of said variable impedance means in proportion to changes in said current; c. means for applying a potential across the serially arranged voltage divider means and variable impedance means, said potential redistributing itself in response to changes to said variable impedance means to maiNtain substantially constant the current through said photomultiplier tube to produce a potential across said divider means that is exponentially related to the light received by said photomultiplier tube; and d. varistor means cooperative with said voltage divider means to develop thereacross a voltage which changes with changes to the voltage across said voltage divider means, said voltage across said varistor being substantially logarithmically related to the light received by said photomultiplier tube.

Claim 9

In combination with a radiation responsive photomultiplier tube: a. voltage divider means for application of potentials to the dynodes of the photomultiplier tube; b. variable impedance means in series with the voltage divider means responsive to the current flow through said photomultiplier tube to vary the impedance of said variable impedance means in proportion to changes in said current; c. means for applying a potential across the serially arranged voltage divider means and variable impedance means, said potential redistributing itself in response to changes to said variable impedance means to maiNtain substantially constant the current through said photomultiplier tube to produce a potential across said divider means that is exponentially related to the light received by said photomultiplier tube; and d. varistor means cooperative with said voltage divider means to develop thereacross a voltage which changes with changes to the voltage across said voltage divider means, said voltage across said varistor being substantially logarithmically related to the light received by said photomultiplier tube.

Claim 10

The apparatus of claim 6 including impedance means in series with said varistor, the said serially arranged varistor and impedance means being disposed in parallel with said voltage divider means.

Claim 11

The apparatus of claim 7 including means for applying a bias voltage across said varistor which is of such a value that when algebraically combined with the voltage produced thereacross by means of said voltage divider means there is no net resultant voltage across said varistor when the radiation received by said photomultiplier tube is at some certain maximum level.