Voltage run-down circuit

Claim 2

In a photometric analysis system including a photoresponsive device for generating a voltage related to the light received by the device, a voltage run-down circuit comprising first and second circuit branches connected in parallel, a capacitor in said first branch and a resistance in said second branch, means for charging said capacitor with a reference voltage, and a comparator for comparing a voltage decay of the reference voltage on said capacitor with the voltage generated in the photoresponsive device, the improvement comprising a resistance in said first branch in series with said capacitor to provide an initial voltage stepdown of the decaying reference voltage applied to said comparator thereby to compensate for inadequate high frequency response in said comparator.

Claim 3

In a photometric analysis system for generating a signal related to the log of a voltage ratio of a reference voltage over a test voltage generated in a photoresponsive device, said system being of the type including a comparator having first and second inputs, said first input being connectable to the photoresponsive device, a voltage run-down circuit including first and second circuit branches connected in parallel, a capacitor in said first branch and a resistance in said second branch, said voltage run-down circuit being connected between said second input of said comparator and a common conductor for said system and means cyclically connected to said voltage run-down circuit for charging said capacitor to the reference voltage, the improvement comprising a resistance in said first branch in series with said capacitor to provide an initial step-down of the run-down voltage when said capacitor starts to discharge to compensate for inadequate high frequency response in said comparator.

Claim 4

In a photometric analysis system for generating a signal related to the log of a voltage ratio of a reference voltage over a test voltage generated in a photoresponsive device, said system being of the type including a comparator having first and second inputs, said first input being connectable to the photoresponsive device, a voltage run-down circuit including first and second circuit branches connected in parallel, a capacitor in said first branch and a resistance in said second branch, said voltage run-down circuit being connected between said second input of said comparator and a common conductor for said system and means cyclically connected to said voltage run-down circuit for charging said capacitor to the reference voltage, the improvement comprising a resistance in said first branch in series with said capacitor to provide an initial step-down of the run-down voltage when said capacitor starts to discharge to compensate for inadequate high frequency response in said comparator.

Claim 5

In a photometric analysis system for measuring concentration of a substance in a liquid, said system being of the type including a comparator having first and second inputs, a photoresponsive device connected to said first input, a voltage run-down circuit including first and second circuit branches connected in parallel, a capacitor in said first branch and a resistance in said second branch, said voltage run-down circuit being connected between said second input of said comparator and a common conductor for said system, means for storing a reference voltage and means for cyclically applying said reference voltage to said voltage run-down circuit and for cyclically applying the output of the comparator to a measuring device when said reference voltage is not being applied to said voltage run-down circuit and said capacitor thereof is discharging, the output of said comparator being a signal which is related to the log of the voltage difference between the reference voltage and the voltage from the photoresponsive device and which can be directly converted to concentration units, the improvement comprising a resistance in said first branch in series with said capacitor to provide an initial step-down of the run-down voltage when the capacitor starts to discharge to compensate for inadequate high frequency response in said comparator.

Claim 6

In a photometric analysis system for measuring concentration of a substance in a liquid, said system being of the type including a comparator having first and second inputs, a photoresponsive device connected to said first input, a voltage run-down circuit including first and second circuit branches connected in parallel, a capacitor in said first branch and a resistance in said second branch, said voltage run-down circuit being connected between said second input of said comparator and a common conductor for said system, means for storing a reference voltage and means for cyclically applying said reference voltage to said voltage run-down circuit and for cyclically applying the output of the comparator to a measuring device when said reference voltage is not being applied to said voltage run-down circuit and said capacitor thereof is discharging, the output of said comparator being a signal which is related to the log of the voltage difference between the reference voltage and the voltage from the photoresponsive device and which can be directly converted to concentration units, the improvement comprising a resistance in said first branch in series with said capacitor to provide an initial step-down of the run-down voltage when the capacitor starts to discharge to compensate for inadequate high frequency response in said comparator.