SU813143A1 - Photoelectric spectrum analyzer - Google Patents

Description

(54) PHOTO-ELECTRIC SPECTRON ANALYZER

I

Invention of optical spectroscopy analyzers.

There are known devices for d - optic analysis of the sample (11.

. The closest to the present invention is an optical analysis device containing two sources of radiation, photogenerators equipped with gain control knobs, linear keys, digital-to-analog amplifiers, null saganes, one of which is connected to gain control knobs, others are connected to control devices that are 4 converters and recording device 23T

However, such devices are characterized by an insufficiently high accuracy of measurements, due to the fact that the gem currents of the photodetector and the drift of amplifiers affect the measurement result.

The purpose of the invention is to improve the measurement accuracy.

This goal is achieved by the fact that the well-known photoelectric spectrum analyzer contains radiation sources, photo-converters equipped with gain control knobs, linear switches, digital-to-analog converters, null saganes, some of which are connected to gain control knobs, others are connected to control devices lazy digital-to-analog converters, and a registering device, is equipped with voltage dividers, and the linear switches are made of three-channel ones, with the output of the first voltage divider, consisting of fixed resistors and connected to the first channel of the first linear switch connected to the first input, the first zero-org &, the output of the second voltage divider consisting of series-connected fixed resistor and the first digital controlled resistor. and connected to the secondary channel of the first linear switch, connected to the first input of the second nullorgan, the output of the third channel of the first linear switch is connected to the secondary inputs of the first and BTqDoro o-organ, the output of the third voltage divider consisting of a constant resistor and the second digital controlled resistor and connected to the first channel. the second linear key connected to the first input of the third null organ, the output of the fourth voltage divider consisting of a constant resistor and the third digital-to-control resistor and connected to the second channel of the second linear key, the first input of the fourth null-sagana, the output of the third channel of the second linear key is connected to the second inputs of the third and fourth null-organs. The drawing shows a diagram of a photoelectric spectrum analyzer. The device contains an optical system 1, sources 2 and 3 of radiation, a photo-receiver 4, a recording main stream, a photo-receiver 5, a recording stream of comparison. The output of the photodetector 4 is connected to the input of the first amplifier 6 and the output of the photoreceiver 5 is connected to the input of the second amplifier 7, the outputs of the amplifiers 6 and 7 are connected to the inputs of the first linear switch 8 and the second linear switch 9, respectively. Linear keys 8 and 9 are three-channel. The output of the first channel of the linear key 8 includes a voltage divider consisting of constant resistors 1O and 11 (R and RJ). The output of this divider is connected to the first input of the zero-body 12. the output of which is connected to the amplifier gain controller b. The second output of the linear switch is connected by a voltage divider consisting of a constant resistor 13 (R3) and a digital controlled resistor 14 (R). You are running this voltage divider connected to the first input of the zero-body 15, the output of which is connected to the pulse key 16, the digital resistor 14 entering the control device. The input of the pulse key 16 is connected to the generator: 17 pulses, and its output to the scaler 18 connected to the digital control resistor 14. The output of the third channel of the linear switch 8 is connected to the inputs of the null organ 12 and 15, the first channel of the linear switch 9 is connected to a voltage divider consisting of a constant resistor 19 (Ry ) and digital control a resistor 20 (R4) connected to the 3.4-conversion device 18. The output of this voltage divider is connected to the first input of the null fgant 21, the output of which is connected to the gain control coefficient {dieng gain of the amplifier 7, the second output of the linear switch 9 is connected to the divider a voltage consisting of a constant resistor 22 (R7) and a digital controlled resistor 23 (Rg); The output of this voltage divider is connected to the first input of the zero-body 24, the output of which is connected to a pulse switch 25 entering the control device 23 „digital controlled resistor The key input 25 is connected to a pulse generator 17, and its output to a scaling device 26 connected to a digital controlled resistor 23 and a recording device 27. A synchronizer 28 is installed to control the operation of the sources 2 and -3 of the radiation and the linear keys 8 and 9 The gain factor controls are set at amplifiers 6 and 7. The device operates as follows. From the radiation of the analyzed sample in the optical system 1, an analytical LINE is released, the luminous flux of which is perceived by the photoreceiver 4, and a comparison line, the luminous flux is directed to the photodetector 5. The same photodetectors alternate with the pulses of a spark. synchronizer 28. There are time intervals between the arcs of the spark and the light pulses of the source 3 during which the photodetectors are not illuminated. Signals from photodetectors are amplified by amplifiers and fed to linear switches. Through one channel of each linear key, the signal that occurs at the time of illumination of the photoreceiver by spark radiation passes through the second channel - the signal that occurs at the moment of illumination with source 3 and through the third - at the moment when the photoreceivers are not illuminated, i.e., the signal due to dark photodetector current and zero offset amplifier. Therefore, from the first channel of the first linear .- key on the voltage divider consisting of resistors 1O and 11 (R and R (,) the signal Ц к, k, + i / f, is allocated: on the divider consisting of resistors 13 and 14 (Rj and R), the signal and the output of the third channel of the first linear key is the signal Urvi f on the divider consisting of resistors 19 and 20 (Rj and R), the signal of the divider consisting of resistors 22 and 23 ( R-.and Rft) signal 0, ig and "a third output: channel of the second linear key signal Ond, where and is a voltage proportional to the intensity of the analytical line from the photodetector 4; 0 - voltage The output is proportional to the luminous flux of the source 3. With a photoreceiver 4; Hz is the magnitude of the signal caused by the dark current of the photoreceiver 4 and the zero offset of the amplifier 6; the gain of the amplifier 6; Uj is the voltage proportional to the light source of the source 5j Ufl- proportional to the intensity of the comparison line from the photodetector 5; the magnitude of the signal due to the dark current of the photo source and the bias of the amplifier 7; Kj is the amplification factor of amplifier 7.,. The voltage from the output of the voltage divider on the resistors Yn 11 supplied to the first input of the zero-body 12 is compared with the voltage of the yy coming to the second input of the zero-body 12. The voltage proportional to the difference - Un from the output of the nullorgan 12 acts on adjusting the gain of the amplifier 6, setting and maintaining the gain so that the indicated spacing approaches zero, i.e. , Hu., U, -K, b., .. 1 Voltage, Ua-K, tUH, Rj-b R From the output of the voltage divider on resistors 13 and 14, supplied to the first input of the null pulse 15, is also compared with voltage Ont, arriving at the second input of the zero-org on 15. The voltage L U - UM from the output of the nullorgan 15 controls the passage of pulses from the generator 17 through the key 16 to the scaler 18. Depending on the sign of the difference L Uj, the number of pulses increases or decreases in the accumulator of the recalculating device 18 and, consequently, the resistance of the digitally controlled ones increases or decreases ezistorov 2O and 14, which controls the scaler 18. Resistor 14 is set such that the voltage. 436, the voltage removed from the voltage divider across resistors 13 and 14 was close to Ut, i.e. . and ", and and", and, K, (2) Simultaneously with the change in resistance of resistance 14, the resistance of resistor 2O changes by the same amount. ; UJ .VJ4lU U. Voltage, b From the output of the divider to resistors 19 and 2O, arriving at the first input of the null organ 21, is compared with the voltage UHJ entering the second input of the same null organ, “Strained AUj- U - UH from the output of the null organ 21 acts on the gain controller of the amplifier 7, setting and maintaining the gain so that the indicated difference of 1fi6 approaches zero, i.e. Un .., HUH. U3.K.i (3) Yau R6 Voltage and .rJirt-Una; From the output of the divider, resistors 22 and 23, coming to the first input of the nullorgan 24, is also compared with Un., Coming to its second input. The voltage uU4 M4 of the zero-organ output controls the passage of pulses from the generator 17 through the switch 25 to the conversion device 26. Depending on the sign of the difference AU, the number of impulses in the storage device 26 increases or decreases, and therefore the resistance of the resistor 23 increases or decreases a recording device 27, which is controlled by the converter 26. The resistance of the resistor 22 is set so that the voltage taken from the voltage divider on the resistors 21 and 22 is close to the voltage , Ie UniH UM U4KiM (4), Simultaneously with the change in the digital resistance of the he resistor 22, the readings of the recording device change. The resistors R P3 5 h 7 can be chosen equal to 1, then from (1) and (2) .k.4 (5)

Learn from (3), (4.) and (5), we get

- Kii "-;

.UjKi-; l U4Ki; U3 R, U4-Ri (6 RR

..

(7)

play- U4

As can be seen from (7), the value of R, the characteristic measurement result, which is recorded by the recording device 27, is determined only by the value of the luminous flux, which characterizes the concentration of the element being analyzed in the sample, and does not depend on the dark current of the photodetectors, as well as from fluctuations of the sensitivity intensities of the main and auxiliary light sources, from fluctuations in the sensitivity of the receivers, and variations in the gain factors of the amplifiers.

Claims (2)

1. Author's certificate of SSS5R No. 541093, cl. О-01 J З / ОО, published. 1975. 2. USSR author's certificate: № 2646489 / 18-25, cl. Q 01 J 3/42, publish 07/17/78.