SU827983A1 - Photometer - Google Patents

Description

mutator 7. The output of the first channel of switch 7 includes a nerve voltage divider consisting of a constant resistor 8 and a digital controlled resistor 9. The output of this voltage divider is connected to the first input of the comparator 10, the output of which is connected to an integrator consisting from the key //. The input of the latter is connected to the pulse generator 12, and the output is connected to a counting device 13 connected to the resistor 9 and the i / 4 recorder. The second inputs of the comparator JO and the differential amplifier are connected to the output of the second channel of the synchronous switch. The output of the third channel of the switch 7 is connected to the second voltage divider, consisting of constant resistors i / 5, the output of which is connected to the first input of the differential amplifier 17, and the output of this amplifier is connected to the gain controller of the photovoltaic converter 6.

The photometer works as follows.

The luminous flux of the source / device 2 is divided into two beams, with one of the beams and passing through the optical path 3, interacting with the sample being analyzed, and falling on the phototransducer 6, and the other falling on the optical path 4, interacting with the reference sample and on photoconverter 5. The light fluxes of each beam are modulated by the modulator 5 so that they fall on the photoconverter 6 at different times and, in addition, between the gaps there are gaps in which the light from the source does not fall on the photovoltage transducer. Signals from the output of converter 6 arrive at switch 7, where they are divided into three channels.

At the output from the switch, the signals received at the moments of illumination of the photoconverter, besides the components caused by the light currents, have a constant component due to the dark current of the photodetector and the offset of the amplifier zero. A voltage equal to the sum of the constant component U and the signal proportional to the luminous flux that has passed through the optical path 4 is separated: on the neipsoM splitter and on the spin (8 and RQ). The sum of the constant component C / t and the signal proportional to the luminous flux, which melted through the optical path 3, is allocated at the second divider (and). At the output of the third channel of the switch, the signal Uj is extracted, depending on the dark current of the photodetector and the zero offset of the amplifier. Thus, the first input of the comparator 10 receives a signal

i.-g and to.

 at /

 R

R ,,

to the first input of the amplifier / 7 comes

signal

and, -im.

I II: i- g

  - p: - Oh. .-i i

and to the second inputs of the compiler of the “differential amplifier, a signal is received and 1,

where t / i is the signal that is prolordional in intensity of the light flux transmitted through the optical channel 4;

f / 2 - a signal proportional to the intensity of the light flux transmitted through the optical channel 3;

Ku - coefficient of the converter 5.

The voltage U / s of the output of the voltage divider on the resistors 8 and 9, which is fed to the first input of the comparator 10, is compared with the voltage Ut, coming to the second of its input. The voltage proportional to the difference AUi f // - UT, from the output of the comparator, controls the passage of pulses from the generator 12 through a pulsed

key // to the scaling device 13. Depending on the sign of the difference At / i, the number of pulses in the accumulator of the scaling device 13 increases or decreases, and consequently, the resistance of the resistor 9 and the readings of the recorder 14 controlled by the scaling device increase or decrease.

The resistance of the resistor 9 is set as follows. So that the voltage U / was close to the voltage U, i.e.

R,

(;

and..

 W

The voltage supplied to the first input of the amplifier 17 is also compared with the voltage t / applied to the second input of this amplifier. Implementation

proportional to the difference Vz - - / t from the output of the differential amplifier acts "and the adjustable gain of the photovoltage converter 6, setting and maintaining the ratio

gain so that the indicated difference is approx | izhalsya to zero, i.e.

RU:

.

T + t;: - “io-. and, K, y. (2)

Taking into account formulas (1) and (2) and the fact that the constant resistors Rs and Ri can be set the same, equal to, we will FOR 65

Claims (1)

Claim A photometer containing a sequentially installed light source, a beam splitter, optical paths, a modulator, a photoconverter with a controlled conversion coefficient, a synchronous switch, a differential amplifier, the output of which is connected to the control input of the photoconverter, and a recorder, characterized in that, 5 in order to improve accuracy, a comparator, two resistor voltage dividers, and an integrator, a synchronous switch are made three-channel, and to its first output through a resist) are introduced into it) a voltage divider made controlled, one of the comparator inputs is connected, the second output is connected to the second input of the comparator and to one of the inputs of the differential amplifier, 5 the second input of which is connected to the third output of the synchronous switch through the second resistor voltage divider, and the integrator is connected between the output of the comparator and control input 3 of the resistor voltage divider and is connected to the registrar.