The electronic unit photometric detector

 

The invention relates to the field of high-performance liquid chromatography. Essence: the electronic unit photometric detector includes a photodetector, the inverter current of the photodetector into a voltage multiplying digital to analog Converter, analog-to-digital Converter and a microcontroller. Inputs/outputs the first port of the microcontroller bitwise connected to the digital inputs/outputs analog-to-digital Converter, an analog input connected to the output of the multiplying digital to analog Converter, the digital inputs which bitwise connected to the outputs of the second port of the microcontroller and analog input is connected to the inverter output current of the photodetector into a voltage, an input connected to the output of the photodetector. The technical result - the reduction of the noise level while maintaining low error and drift. 1 Il.

The invention relates to the field of high-performance liquid chromatography.

Known electronic unit photometric detector [1], containing a working sensor, reference sensor, the Converter current work of the photodetector into a voltage, a current transducer opasnostjami are the high level of uncertainty and drift, there is no perfect matching characteristics of the working and reference photodetectors.

The closest to the technical nature of the claimed device is selected as a prototype of an electronic unit photometric detector [2], which contains the sensor, the Converter current of the photodetector into a voltage analog-to-digital Converter and a microcontroller, the output of the photodetector is connected to the input transducer of the photodetector into a voltage, the output of which is connected to the analog input of analog-to-digital Converter, digital inputs/outputs which bitwise connected to inputs/outputs of the first port of the microcontroller.

This electronic unit has small values of error and drift, as a worker, and the reference luminous flux alternately served on the same photodetector. However, its disadvantage is the weak suppression of low frequency noise of the photodetector due to the fact that the cutoff frequency of the Converter current of the photodetector into a voltage and an analog part analog-to-digital Converter must be significantly higher than the modulation frequency of the light flux (typical value of which is equal to 12.5 Hz).

Task is okresnosti and drift.

This is achieved in that the electronic unit photometric detector containing the sensor, the Converter current of the photodetector into a voltage analog-to-digital Converter and a microcontroller, the output of the photodetector is connected to the input transducer of the photodetector into a voltage, and the digital inputs/outputs a / d Converter bitwise connected to inputs/outputs of the first port of the microcontroller, provided with a multiplying digital to analog Converter, an analog input connected to the inverter output current into a voltage, digital inputs bit-wise connected to the outputs of the second port of the microcontroller, and the output connected to the analog input of analog-to-digital Converter.

The invention is illustrated "blueprints", which shows the structural diagram of the electronic unit photometric detector. The device comprises a photodetector 1, the Converter current sensor voltage 2, multiplying d / a Converter 3, an analog-to-digital Converter 4 and the microcontroller 5, the inputs/outputs of the first port bitwise connected to the digital inputs/outputs analog-to-digital Converter with 4 analog input which is tive to the outputs of the second port of the microcontroller 5, and the analog input is connected to the inverter output current of the photodetector into a voltage 2 input connected to the output of the photodetector 1.

The electronic unit photometric detector works as follows. Using optical-mechanical detector (not shown) on the photodetector 1 in turn serves the working and the reference light streams. It converts the intensity into electric current. The Converter current sensor voltage 2 converts this current into an electrical voltage, which, through the multiplying d / a Converter 3 is supplied to an analog-to-digital Converter 4. Through the multiplying d / a Converter 3 is multiplied subject to analog-to-digital conversion of the voltage is stepped suppressing the weight function (EOF) in accordance with the expression

where U2(t), U3(t) - output voltages respectively of the Converter current sensor voltage 2 and multiplying digital to analogue Converter 3;

n is the number of stages EOF;

i(t) is the unit function, equal to 1 at the (i-1)T<tiT and 0 otherwise;

When this weighting coefficients wiare fed to the digital inputs of the multiplying digital to analogue Converter 3 outputs the second port of the microcontroller 5.

Analog-to-digital Converter 4 converts the digital code average over the time interval PT values of the voltage U3(t). The numeric equivalent of the output of the code is described by the following expression:

where K is a constant coefficient;

w(t) - EOF generated by the multiplying digital to analogue Converter 3.

Process control analog-to-digital conversion is performed by the microcontroller 5. It also synchronizes the beginning of the cycles of formation of EOF and analog-to-digital conversion with the switching times of the luminous flux. Thus, the numeric equivalent of the output code of the analog-digital Converter 4 is directly proportional to the intensity of the light flux received on the photodetector 1 during the current conversion cycle.

The results of the analog-to-digital conversion of the intensities of the working and the reference light fluxes received at the microcontroller, through which calculates the optical density.

Weight FCP is allowing EOF [3] allows to suppress noise of the photodetector 1 in several thousand times in the frequency range from (2...3)/TPto infinity (where TP is the duration of the interval of supply of the working or reference luminous flux at the input of the photodetector 1). A similar suppression in the absence of the weight averaging due to the filtering properties of the Converter current sensor voltage 2 and analog-to-digital Converter 4 is possible only in the frequency range from 30...40)/TP.

Thus, this device allows for a significant decrease noise while maintaining the possibility of modulation of the light flux, and consequently, low values of error and drift.

Claims

The electronic unit photometric detector containing the sensor, the Converter current of the photodetector into a voltage analog-to-digital Converter, microcontroller, I/o port which is the bitwise connected to the digital inputs/outputs analog-to-digital Converter, the output of the photodetector is connected to the input transducer of the photodetector into a voltage, characterized in that it has a multiplying digital to analog Converter, an analog input connected to the inverter output current into a voltage, digital inputs bit-wise connected with the indicator.

 

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