SU1711060A1 - Nitrate meter - Google Patents

Abstract

The invention relates to the field of measurement technology, namely to the means of potentiometric control over the content of nitrate ions in aqueous solutions, and can be used in the food industry, agrochemistry, soil science and in scientific research. The purpose of the invention is to increase measurement performance by reducing setup time by automating calibration processes. In the variable voltage block, a full automatic compensation is made of the constant component of the EMF of the electrode system, which occurs in a solution with a concentration of nitrate ions C1 and is fed through the input stage, working as a follower, to the first input of the compensation cascade. When the first button is pressed, the pulse of positive polarity generated by the start element zeroes the first and second. RS triggers and the first digital-to-analog converter, the automatic compensation process begins. The digital comparator analyzes the state of the liquid crystal display (LCD) and, when it is zeroed, produces a signal controlling the state of the second RS-trigger & which stops the operation of the first digital-to-digital converter and fixes the end of the process of automatic compensation. The second calibration unit in the solution with the concentration of nitrate ions Ci is automatically entered the value of the proportionality coefficient set by the method of sample preparation. The calibration process starts when the third button that nulls the third analog-to-digital converter is pressed, and it ends when it is released, as soon as the known concentration value of nitrate ions Ci is displayed on the LCD. The first calibration unit in a solution with a concentration of nitrate ions C2. The range of measured concentrations is automatically set. The calibration process starts when the second button is pressed, which resets the second digital-to-analog converter, and ends when it is released, as soon as the known value of the nitrate C2 ions is displayed on the LCD. During calibrations, the range switch automatically switches the LCD display range. 3 hp f-ly, 1 ill. U) with about about about

Description

The invention relates to a measurement technique, namely, to means of potentiometric control over the content of nitrate ions in aqueous solutions, and can be used in the food industry, agrochemistry, soil science and in scientific research.

The purpose of the invention is to increase measurement performance by reducing setup time by automating calibration processes.

The drawing shows the functional scheme of nitratomers.

The nitratometer consists of input 1 stage 1, stage 2 compensation, variable voltage unit 3 (BRI), first calibration unit 4, second calibration unit 5, range switching unit 6, analog-anti-log converter (AAP) 7, analog-digital a converter (ADC) 8, a liquid-crystal display (LCD) 9, the first 10 and second 11 switches, and a two-pole power supply stabilizer 12.

The output of the input stage 1 is connected to the first input of the compensation stage 2, to the second input of which the output of the BRN 3 is connected. The output of the compensation stage 2 / is connected to the first input of the BRN 3, to the first input of the first calibration unit 4 and through the first input of the second switch 11 to the input of the ADC 8. The first input of the AAP 7 is connected to the output of the first calibration unit 4, the second input to the output of the second calibration unit 5, and the third input to the output of the range switching unit 6. Through the first input of the first switch 10 and the second input of the second switch 11 of the A / D converter 8 is connected to the output of the input stage 1 and through the second inputs of the first 10 and second 11 switches with the AAP output 7. The output of the A / D converter 8 is connected to the LCD 9 input.

The BRN 3 consists of an analog comparator 13, the input of which is the first input of the BRN 3; the first element 2I-NOT 14,

SECOND INPUT OF WHICH IS SECOND IN

house BRN 3 and is connected to the first output of the two-pole power supply stabilizer 12; the second element 2I-NOT 15, the second input of which is the third input of the RTS 3 and is connected to the second output of the two-pole power supply stabilizer 12, the second input of the first calibration block 4 and the input of the second calibration block 5; the third element 2.IN- NOT 16;. the first RS flip-flop 17, the S-input of which is connected to the output of the analogue computer 13, the Q-output is connected to the first input of the first element 2IHE 14, and the Q-output to the first input of the second element 2I-NOT 15; start element 18; the first button 19 and Digital comparator 20, the input of which is the fourth input; BRN 3 if is connected to the output of the ADC 8 ;. the second RS-flip-flop, the S-input of which is connected to the output of the digital comparator 20; the first D / A converter 22, the V-input of which is connected to the Q-output of the second RS flip-flop 21, and the C-input to the output of the third element 2I-NOT 16; the first inverting amplifier 23, the output of which is the output of the BRN 3, and the input is connected to the output of the first DAC 221

The third element 2I-NOT 16 is connected by the first input to the output of the first element 2IHE 14, and by the second input to the output of the second element 2I-NOT 15, the Start element 18 is connected by input to the first output of the first button 19 and the output to the R-input of the first 17 and the second 21 RS-flip-flops and the first DAC 22.

The first calibration block 4 consists of. the second inverting amplifier 24, the output of which is the output of the block, the first input is the first input of the block, and the second input is connected to the output of the second DAC 25, the C input of which is the second input of the block: and the V and R inputs are connected respectively: first and second inputs of the second button 2 &, the output of which is connected to the common bus. i

The second calibration block 5 consists of a third button 27, a third inverting amplifier 28, the output of which is the output of calibration block 5, and the input is connected to the output of the third DAC 29, whose C input is the input of calibration block 5, and V- and I- the inputs are connected respectively to the first and second inputs of the third button 27, the output of which is connected to the common bus .:

The operation of the nitratomer is based on the principle of direct potentiometric measurement of the activity of one-charge anions of the MOz-controlled sample using an electrode ion-selective system with electronic AARP EMF of the electrode system in the sample in the value of nitrogen concentration of nitrates in the sample. The EMF of the electrode system, placed in a controlled sample, is fed to the input stage 1, working as a repeater.

There are three measurement modes in the nitratomer: the mode of measuring the EMF of the electrode system, the mode of measuring the increment of the EMF of the electrode system, and the mode of measuring the nitrogen concentration of nitrates.

In the mode of measuring the EMF of the electrode system, through the depressed second 11 and pressed first 10 switches, this voltage from the output of the input stage 1 is fed directly to the input of the ADC 8 and then to LCD 9, which indicates the emf value in millivolts. In this mode, the nitratomer works as a high-resistance millivoltmeter.

In the concentration measurement mode, the EMF of the electrode system in the sample being measured is converted to the nitrogen concentration of nitrates in accordance with the static conversion function

lqЈi from the ky,

where C is the concentration value, mg / kg;

S (56+ 6) MB / pN03l

rmoz-negative decimal logarithm of the activity of ions of the MO3;

Ei - EMF of the electrode system in a calibration solution with a concentration of nitrate ions Ci;,,

B- EMF of the electrode system in a solution with an unknown, measured concentration of nitrate ions

K - coefficient of proportionality established by the method of sample preparation.

To implement the EMF conversion function - concentration: the following cascades are intended; BRN 3, calibration blocks 4 and 5, compensation stage 2 and AAR 7. These stages are used to calibrate the instrument in three calibration solutions with a known concentration of d, C2, C3. In BRN 3, together with the compensation stage 2, a full automatic compensation of the constant voltage component of the electrode system is performed. When electrodes are placed in a solution with a known nitrogen concentration of nitrates, d-i dropping at the output, compensation stage 2, enters the input of the analog comparator 13 and through the pressed second switch 11 to the input of the ADC 8 and then displayed on LCD 9.

When the first button 19 is pressed, the process of automatically compensating for this voltage begins. In this case, a positive polarity pulse is formed at the output of the start element 18. This impulse arriving at the R-inputs of the first 17 and second 21 RS-flip-flops / and the first DAC 22, they are set to zero. At the direct Q-output of the first RS-flip-flop 17, a unit signal is set that is allowed to pass through the first 14 and third 16 elements 2I-HE rectangular pulses from the first output of the dual-pole power stabilizer 12 to the C-input of the first DAC 22, and on the inverse Q-output of the second RS-tr of the igger 21, a zero signal is set, which is enabling for the V-input of the first DAC 22. The pulse counting process begins. The binary input code of the first DAC 22 is converted into a current that is fed to the input of the first inverting amplifier 23. As the binary number increases, the total input current of the first inverting amplifier 23 increases.

current is in voltage and transmits it to the second input of cascade 2 compensation. The resulting voltage at its input, decreasing, reaches the value at which;

The output of the analog comparator 13 is in accordance with a Vits voltage, the head of which the first RS flip-flop 17 is transferred to the unit state. At the inverse b-output of the first trigger 17, a unit-to-k signal will be set ;.

0 tsi, which is permissive for passing through the second 15 and third 16 elements 2И-НЁ rectangular impulses from the second generator, a two-field rnrp power supply stabilizer 12 to the C-vhrd of the first DAC

5 22. Moreover, the frequency of the pulses of the second generator is significantly less than that of the first generator. Therefore, the counting process is significantly slowed down.

Big frequency of the first generator

0 is selected to accelerate the calibration time, and the frequency of the second generator is aligned with the period for establishing the readings of the A / D converter 8, in order to clearly fix the LCD zero reset, which corresponds to a full

5 compensation of the constant component of the EMF of the electrode system. At the same time, at the output of the digital comparator 20, the signal of unit turns on, which will switch the second RS flip-flop 21 to the unit state. Unity-

The 0 signal at the inverse Q-output of the second P5-trigger pa21 will disable the counting pulses of the first DAC 22. The counting process stops, the output voltage of the first inverting amplifier 23 is fixed and

5, the second switch 11 is pressed.

The second calibration unit 5 serves to introduce into the conversion process the emf-concentration value of the proportionality coefficient established by the sample preparation method. In a solution with a known concentration of nitrates O at the first 10 and second 11 switches pressed by the second calibration unit 5, the initial current AAR 7 is set so that the concentration value d is indicated on LCD 9.

The calibration process takes place as follows. When the third button 27 is pressed, the signal of the unit is set at the R input of the third DAC 29, and the input signal is zero at y0, and the pulse counting / input process starts at the C input from the second generator of the dual polarizing power supply stabilizer 12. The binary output of the third D / A converter 29 is converted into a current, which is fed to the input of the third inverting amplifier 28. The output voltage of the third inverting amplifier 28, proportional to the change in AARP 7, through the second 11 and first 10 switches enters the ADC 8 and then displayed on LCD

9. As soon as the known value of the Ci solution concentration is displayed on the LCD 9, the button 27 is pressed. At the V input of the third D / A converter 29, a unit signal is established and the counting process is stopped, and the output voltage of the third inverting amplifier 28 is fixed. .

When calibrating in solution with a concentration of nitrate ions C2, the transmission coefficient of the first calibration unit 4 is established so that the LCD 9 indicates the value of the concentration C2 in the previously selected units. Process ka- The calibration is as follows. When the button 26 is pressed, the unit signal, set on the R-lead of the second DAC 25, is set. and at the V input, a zero signal begins the process of counting pulses from the second generator of a two-pole power supply stabilizer 12. The binary output code of the second DAC 25 is converted into a current which is supplied to the second input of the second inverting amplifier 24. At the first input of the second inverting amplifier 24, the output voltage of the compensation stage 2 is obtained, -from the increment of the EMF of the electrode system in the C2 solution relative to the Ci solution. The resulting output voltage of the second inverting amplifier 24 changes in proportion to AARP 7, through the second 11 and first 10 switches enters the ADC 8 and then is displayed on LCD 9. Once the LCD | 9 shows a known value of the concentration of the C2 solution, the second button 26 pressed. At the Y input of the second DAC 25, a unit signal is established and the counting process is terminated, and the output voltage of the second inverting amplifier 24 is fixed.

After appropriate calibration in solutions with a known concentration of Ci and C2, when the electrode system is placed in a solution with a concentration of C3 (C1 C3 C2), the LCD 9 of the nitratomer indicates concentration. radios. Cs in previously selected measurement, measurement. When calibrating and measuring, the range switching unit b automatically switches the LCD indication ranges 9.Is

The bipolar power supply stabilizer 12 provides all the nodes and stages of the device with a stabilized supply voltage in which the first generator is used for the voltage converter, and the second generator for the operation of the circuit; supply voltage control of bipolar power supply stabilizer 12.

Measurement of the increment of the EMF of the electrode system is made in. calibration time during the transition from solution to solution. The measurement result is read on the LCD 9 when the second switch 11 is pressed. According to the measurement results of the EMF increment

the electrode system in the C2 solution compared with the Ci solution establishes the compliance of the nitrate electrode with the technical requirements for it.

Advantages of the technical solution

The nitratomer described in comparison with the known one means that the tuning time is reduced by the introduction of automatic calibrations, which improves the measurement performance.

Claims (4)

1.Nitratomer, containing compensation stage, two switches, two calibration units, adjustable voltage unit, analog-anti-log converter, analog-digital converter, range switching unit, liquid-crystal indicator, two-pole power supply stabilizer and input stage, the output of which is connected with the first the input of the first switch and with the first input of the compensation stage connected by the second input to the output of the variable voltage block and the output to the first inputs of the first calibration block and the second the switch, the analog-anti-log converter block is connected by the first and second inputs to the outputs of the first and second calibration blocks, respectively; the third input is connected to the output of the range switching unit and the output to the second input of the first switch, the output of which is connected to the second input of the second switch connected by an output to the input of an analog-to-digital converter, the output of which is connected to the input of a liquid-crystal indicator, characterized in that, in order to increase the measurement performance th by reducing the time setting by automating the calibration processes, in it the variable voltage block is connected by the first input to the output of the compensation cascade, the second input to the first output of the dual polar power regulator, the third input to the second output of the dual polarity power stabilizer, to the first input of the first calibration block and to the input the second calibration block, the fourth input - to the analog-digital output converter 2. A nitratomer according to claim 1, in which it is so that, in it, the variable voltage block contains the first inverting amplifier, two triggers, and the start element. the first button, the digital .comparator, the three elements 2I-NOT, the first digital analog converter and the analog comparator, the input of which is the first input 6p: 0 ka, the output of the analog comparator is connected to the S input of the first trigger, the direct and inverse outputs of which are connected to the first inputs of the first and second elements 2VI-HEi, the second inputs of which are respectively the second and the third inputs of the block, the outputs of the first and second elements 2I-NOT are connected respectively to the first and second inputs of the third element 2I-NOT, the output of which is connected to the C input of the first digital-to-analogue converter connected by the R input to the R inputs of both trigger trench and to the output of the start element, V-vho.dom - inverse to the output of the second flip-flop and the output - to the input of the first inverting amplifier, whose output is vtshodom unit, the first button connected | the first pin to the input of the start element and the second pin to the common bus, and the digital comparator, whose input is the fourth input of the block, is connected by an output to the 3 input of the second trigger. 3. A nitratomer according to claim 1, in accordance with clause, so that in it the first calibration block contains a second digital-to-analog input device. The second button and the second inverting amplifier, the first input and output of which are respectively the first input and output of the block, and the second digital-to-analog converter, whose C input is the second input of the block, is connected by an output to the second input of the second inverting amplifier and V- and R - inputs respectively to the first and second inputs of the second button, the output of which is connected to a common bus. 4. Nitratomer according to p; 1, so that in it the second calibration block contains a third digital-to-analog converter, a third, a button and a third inverting amplifier, the output of which is the output of the block, and the third digital-to-analog converter, C- the input of which is the input of the unit, is connected by an output to the input of the TpeTberoviHBepTHpyKiiitero amplifier and V- and R-input, respectively, to the first and second inputs of the third button, the output of which is connected to the common bus, ..,: