Ratiometric transparency meter

Claim 1

In the control and measurement of a physical parameter P X in response to a voltage controlled energy source, an apparatus for ratiometrically measuring P X in a particular setting S X by comparison to the value P R obtained for such parameter in a reference setting S R , which comprises: two voltage controlled energy sources L 1 , L 2 ; a sensor D 1 exposed to the combined effect of L 1 and L 2 , and having an electrical output signal proportionally responsive to the combined powers of L 1 and L 2 ; a sensor D 2 exposed to the effect of L 1 through S X and to the effect of L 2 through S R , having an electrical output signal proportionally responsive to the combined effects of L 1 through S X and of L 2 through S R ; means for impressing a square-wave-shaped voltage supply V 2 to L 2 ; means for impressing a continuous voltage supply V 1 to L 1 ; means for regulating the voltage supply impressed upon one of said energy sources in proportion to the intensity of the effect of the other energy source upon D 2 ; means for detecting the output signal amplitude U T .sbsb.P of D 1 during the peak period T P of V 2 and the output signal amplitude U T .sbsb.V of D 1 during the valley period T V of V 2 . whereby P X can be determined from the equation: P.sub.X =(P.sub.R U.sub.T.sbsb.V /U.sub.T.sbsb.P -U.sub.T.sbsb.V)

Claim 3

The apparatus claimed in 1, wherein said means for regulating comprises: means for separating the output signal Y of D 2 into two wave-forms corresponding to the intensity of the effect of L 1 and to the intensity of the effect of L 2 respectively upon D 2 ; means for comparing the amplitude of said two wave-forms; and means, responsive to the output of said means for comparing, for controlling the voltage supply impressed upon one of said energy sources.

Claim 6

The apparatus claimed in 2, wherein said means for separating comprises: an input non-inverting operational amplifier Z 1 having its input connected to the output of D 2 ; an inverting operational amplifier Z 2 having a gain G 1 , where G 1 = -6; a capacitor linking the output of Z 1 to the input of Z 2 ; and a diode means in the feed-back loop of Z 2 to suppress its positive output excursion; said means for comparing comprises: a summing junction having two inuts; a linking resistor between the output of Z 1 and one of the summing junction inputs; a linking resistor between the output of Z 2 and the other summing junction inputs; and an integrating operational amplifier Z 3 having its input connected to the summing junction; said means for controlling comprises: a cathode follower circuit driving L 1 having its input connected to the output of Z 3 .

Claim 7

The apparatus claimed in 2, wherein said means for separating comprises: means for generating a negative continuous signal having an amplitude A proportional to the output signal amplitude Y T .sbsb.P of D 2 during the peak period T P of V 2 ; means for generating a positive continuous signal having an amplitude B proportional to the output signal amplitude Y T .sbsb.V of D 2 during the valley period T V of V 2 ; said means for comparing comprises: means for summing B with 1/2 A.

Claim 8

The apparatus claimed in 6, wherein said means for generating a negative signal comprisis: sample-and-hold circuit H 1 ; an inverting operational amplifier combined with H 1 ; and means for applying T T .sbsb.P to H 1 . said means for generating a positive signal comprises: a sample-and-hold circuit H 2 ; a non-inverting operational amplifier combined with H 2 ; and means for applying Y T .sbsb.P to H 2 .

Claim 9

The apparatus claimed in 7, wherein said means for applying Y T .sbsb.P to H 1 comprises: switch means for connecting the output of D 2 to H 1 during T P ; and said means for applying Y T .sbsb.V to H 2 comprises switch means for connecting the output of D 2 to H 2 during T V .

Claim 10

The apparatus claimed in 2, wherein said means for separating comprises: means for generating a square-waved signal SWG; an amplifier Z 8 connected to the output of D 2 , having a gain G T .sbsb.P during the peak period T P of SWG where G T .sbsb.P = 1/2 G T .sbsb.V ; sample-and-hold means H 3 connected to the output of Z 8 ; switch means controlled by SWG for disconnecting H 3 during T V ; and switch means controlled by SWG for changing the gain controlling feed-back loop characteristics of Z 8 . said means for comparing comprises: a differential input amplifier Z 9 having its non-inverting input connected to the output of said sample-and-hold means; switch means controlled by SWG for applying the output of Z 8 to the inverting input of Z 9 during T V said means for controlling comprises: a cathode follower circuit controlled by the output of Z 9 during L 2 .

Claim 11

The apparatus claimed in 9, wherein the inverting input of Z 9 is permanently connected to a saturating voltage through a resistor; and said sample-and-hold means comprises a capacitor connected between the non-inverting input of Z 9 and the common.