CN102866180A - High-precision intelligent acidity meter and measuring method thereof - Google Patents

Abstract

The invention discloses a high-precision intelligent acidity meter and its measurement method. Its A/D conversion circuit includes a temperature sensor, a PH sensor, a first operational amplifier, a second operational amplifier, a multi-channel analog switch and an A/D converter. The outputs of the sensor and the pH sensor are respectively connected to multiple input terminals of one channel of the multi-channel analog switch through the first and second operational amplifiers, and the multi-channel analog switch is connected to the feedback circuit of the second operational amplifier, and the two channels of the other channel Resistors with different resistances are respectively connected to the output terminals. The measuring method of the present invention adopts the calibration method of automatically identifying the standard liquid during one-point and two-point calibration, and simultaneously adopts the method of temperature compensation to calibrate the pH values of the standard liquid and the measured liquid. The invention can automatically identify the pH value of the calibrated standard solution, can calibrate the pH value of the standard solution according to the ambient temperature, reduces manual operations, and greatly improves the measurement accuracy of the pH value.

Description

High precision intelligent acidity meter and its measuring method

technical field

The invention discloses a high-precision intelligent acidity (PH) meter and a measuring method thereof, belonging to the field of electronic measurement and control.

Background technique

With the development of scientific research and the progress of production technology, the quantitative analysis of moisture has been listed as one of the basic items of physical and chemical analysis of various substances. As an important quality index of various substances, its pH value is the most important important data. In addition, the requirements for the measurement and control of the pH value of liquid and solid mixtures in the production process or in environmental protection are also increasing, so the use of acidity meters as analytical instruments is becoming more and more popular. The acidity meter is referred to as a PH meter, which consists of two parts: an electrode and a measuring circuit. If the electrodes can be maintained reasonably, the standard buffer solution can be prepared according to the requirements, and the electrometer can be operated correctly during use, the error of pH indication can be greatly reduced, thereby improving the reliability of chemical experiment and medical inspection data.

Most of the existing pH meters are calibrated manually, and the temperature compensation is also carried out by manually adjusting the knob. This method has the defects of cumbersome operation, great influence of the environment and low accuracy. At the same time, the maintenance workload of the pH meter used in the production process is very heavy. For example, the pH may often have zero drift and range changes. The manual calibration of the pH meter requires a large workload and affects the normal measurement work of the pH meter. In order to overcome the above shortcomings, it is the development trend of intelligent pH meters to replace manual calibration with automatic calibration and increase the function of automatic temperature calibration.

The automatic calibration device of the pH meter has developed rapidly in recent years. Its development is based on the automatic cleaning device of the pH meter and the online self-diagnosis function of the sensor. accurate. The sensor can provide basic data for the automatic calibration of the pH meter.

Contents of the invention

Technical problem: most of the existing pH meters are calibrated manually, and the temperature compensation is also carried out by manually adjusting the knob. This method has the defects of cumbersome operation, great influence of the environment and low precision. At the same time, the maintenance workload of the pH meter used in the production process is very heavy. For example, the pH may often have zero drift and range changes. The manual calibration of the pH meter requires a large workload and affects the normal measurement work of the pH meter.

Generally, the concentration of the standard solution is the pH value measured at an ambient temperature of 25°C. When the ambient temperature changes, the pH value of the standard solution will also change; most of the current pH meters do not have a temperature correction function, which affects the The measurement accuracy of pH value.

At the same time, for different standard solutions and solutions to be tested, the mV value of the solution output by the pH electrode has a large range. After being amplified by the operational amplifier, it is generally 0 ~ ± 1999.9mV; Amplification, such that for some small signals, the resolution is reduced by using a large range of conversion, and it also affects the measurement accuracy of the low-concentration pH value.

In addition, the standard solutions used for calibration are generally fixed about 3 kinds, and the pH meter must obtain the pH value of these standard solutions to calculate; the conventional pH meter is manually input the pH value of the solution during one-point calibration and two-point calibration , which is not only inconvenient to operate and use, but also may cause human error.

Technical solution: The purpose of the present invention is to overcome the above-mentioned defects of the traditional PH meter, and propose a high-precision intelligent acidity (PH) meter and its measurement method, adopting the following technical solution:

A high-precision intelligent acidity meter comprises a single-chip microcomputer circuit, an A/D conversion circuit, a man-machine interface circuit and a power supply circuit, and the A/D conversion circuit and the man-machine interface circuit are respectively connected to the single-chip microcomputer circuit, and is characterized in that the A/D conversion The circuit includes a temperature sensor, a pH sensor, a first operational amplifier, a second operational amplifier, a multi-channel analog switch and an A/D converter, and the outputs of the temperature sensor and the pH sensor are respectively connected to the multi-channel analog switch through the first and second operational amplifiers Multiple input ends of one of the channels, the output end of one of the channels is connected to the A/D converter, and the output end of the other channel of the multi-channel analog switch is connected to the inverting input end of the second operational amplifier, the said Two of the input terminals of the other channel are respectively connected to resistors with different resistance values for range switching, and the address terminals of the multi-channel analog switch are connected to the single-chip microcomputer circuit.

The measurement method of the high-precision intelligent acidity meter is characterized in that the temperature compensation method uses a temperature sensor to measure the ambient temperature, corrects the standard solution at a non-standard temperature, and the single-chip circuit uses different formulas to calculate according to different temperature ranges to obtain the environmental temperature The pH value of the standard solution under the temperature, the concrete method is as follows:

When correcting by one point:

0°C～50°C PH ₁ =0.0000483t ₁ ² -0.001266t ₁ +4.004...(1)

50°C～60°C PH ₁ =0.0000483t ₁ ² -0.001266t ₁ +3.994...(2)

Wherein, PH ₁ represents the measured pH value of one-point calibration standard solution, and t ₁ represents the measured ambient temperature value of one-point calibration;

During two-point calibration:

0°C～50°C PH ₂ =0.00006875t ₂ ² -0.006311t ₂ +6.979...(3)

50°C～60°C PH ₂ ＝0.0000776t ₂ ² -0.01268t ₂ +9.453...(4)

Wherein, PH ₂ represents the measured pH value of the two-point calibration standard solution, and t ₂ represents the measured ambient temperature value of the two-point calibration.

When performing one-point calibration and two-point calibration, according to the millivolt value of the standard solution measured by the pH sensor, after being amplified by the operational amplifier, the single-chip circuit collects the amplified millivolt value, and according to the millivolt value range of different standard solutions Automatic identification of standard solutions.

Beneficial effect:

1, the acidity meter of the present invention adopts the automatic switching of measuring range, constitutes two kinds of different feedback circuits with the resistance of different resistance value, is connected with 2 input channels of multi-channel analog switch, single-chip microcomputer selects corresponding analog switch channel address by selecting The channel, according to the mV value of the solution output by the pH electrode, realizes automatic switching between the range of 0~±399.9mV and 0~±1999.9mV, avoiding the conversion of small signals to large ranges (as the saying goes, large scales are called small objects), and improve It improves the resolution of small signals and improves the measurement accuracy of low-concentration solutions.

2. In the acidity meter of the present invention, the multi-channel analog switch is connected in the feedback circuit of the operational amplifier, and the on-resistance of the multi-channel analog switch is used as a part of the feedback resistance of the operational amplifier, which eliminates the loss of the measured signal at the analog switch on-resistance , improving the measurement accuracy.

3. The acidity meter of the present invention uses a temperature sensor to measure the ambient temperature, corrects the standard solution at a non-standard temperature (25°C), calculates with different formulas according to different temperature ranges, and obtains the standard solution at the ambient temperature. PH value, in order to carry out temperature compensation, improve the measurement accuracy.

4. When performing one-point calibration and two-point calibration, the acidity meter of the present invention can automatically identify the pH value or concentration of the standard solution according to the measured millivolt (mV) value of the standard solution, without manual input, reducing the workload , avoiding the errors that may be caused by manual operation, and improving the degree of automation.

5. The pH meter and its measurement method of the present invention greatly improve the stability of the pH meter and can achieve a measurement accuracy of 0.001.

Description of drawings:

Figure 1 is a structural diagram of the patented high-precision intelligent acidity (PH) meter of the present invention.

Fig. 2 is a hardware circuit diagram of the patent of the present invention.

Fig. 3 is a schematic diagram of the scope of the pH value of the standard solution output by the patented pH electrode of the present invention.

Detailed ways

Below in conjunction with accompanying drawing, the present invention is described in further detail:

As shown in FIG. 1 is a structure diagram of a high-precision intelligent acidity (PH) meter of the present invention. The pH meter includes a single-chip microcomputer circuit 1, an A/D conversion circuit 2, a power supply circuit 3, and a man-machine interface circuit 4. The power supply circuit 3 supplies power to the single-chip microcomputer circuit 1, the A/D conversion circuit 2, and the man-machine interface circuit 4 respectively. The A/D conversion circuit 2 and the man-machine interface circuit 4 are connected to the single-chip microcomputer circuit 1 respectively. The single-chip microcomputer circuit 1 uses a single-chip microcomputer as the core to collect and calculate data. The man-machine interface circuit 4 includes LCD, keyboard and buzzer for displaying, inputting information and alarming. The A/D conversion circuit includes a temperature sensor (to measure temperature), a pH sensor (to measure pH value), a first operational amplifier (to amplify the output signal of the temperature sensor), and a second operational amplifier (to amplify the output signal of the pH sensor) , Multi-channel analog switch (realize signal transmission under the control of single-chip microcomputer) and A/D converter (convert analog signal into digital signal for processing by single-chip microcomputer).

The circuit diagram of the high-precision intelligent acidity (PH) meter of the present invention is shown in Figure 2, RS, R/W, E of LCD12864 in the man-machine interface circuit 4 and P1.3 of the single-chip microcomputer U1 (AT89C52) of the single-chip microcomputer circuit 2, P1.2, P1.1 connection, ports P0.0, P0.1, P0.2, P0.3, P0.4, P0.5, P0.6, P0.7 and P1.4 of AT89C52 are connected to people respectively The keyboard and buzzer in the computer interface circuit 4 are connected, and the ports P1.7, P2.7, P2.6, P2.5, P2.4, P2.3, P2.2, P2 of the AT89C52 of the microcontroller circuit 2. 1. P2.0, P3.5, P3.4, P3.2 and P3.6 and D1, D2, D3, D4, D5, B1 of A/D converter U8 (7135) in A/D conversion circuit 2 , B2, B4, B8, POL, OR, -STB and R/-H are connected. The A/D conversion circuit 2 also includes a clock circuit composed of 555, capacitors C9, C8 and sliding rheostats R9, R12.

The signal output terminal of the temperature sensor U9 (AD590) is connected to the non-inverting input terminal of the first operational amplifier M1 (LM301), and the output terminal of the first operational amplifier M1 is connected to the input terminal X3 of the X channel of the multi-channel analog switch U7 (4052). The signal output terminal of the pH sensor U11 is connected to the non-inverting input terminal of the second operational amplifier M2 (LM301), and the output terminal of the second operational amplifier M2 is connected to the input terminals X0 and X1 of the X channel of the multi-channel analog switch U7. The output terminal X of the X channel of the multi-channel analog switch U7 is connected to the +IN and -IN terminals of the 7135, and the output signal is converted into a digital signal by the 7135 for processing by the single-chip microcomputer.

The Y channel output terminal Y of the multi-channel analog switch U7 is connected to the inverting input terminal of the second operational amplifier M2. The Y channel input terminals Y0 and Y1 of the multi-channel analog switch U7 are respectively connected to resistors R14 (75K) and R15 (4.5K) with different resistance values. The address terminals A and B of the multi-channel analog switch U7 are respectively connected to ports P1.6 and P1.5 of the single-chip microcomputer, and the single-chip microcomputer selects the corresponding channel according to the mV value of the solution output by the pH electrode, so that the resistance R14 or R15 and the multi-channel analog The on-resistance of the switch forms a series connection, and as the feedback resistance of the second operational amplifier M2, on the one hand, it can realize the automatic switching between the range of 0-±399.9mV and 0-±1999.9mV, and on the other hand, it can also eliminate the signal under test. The loss of the on-resistance of the analog switch improves the measurement accuracy.

1. Measurement method

1.1, preset

PH ₀ =7.593 SLOPE ₀ =0.19841t+54.195

PH ₀ means the preset pH value, and SLOPE ₀ means the preset slope.

1.2. One-point correction

Sampling mV ₁₀ shows PH ₁₀ = PH ₀ -mV ₁₀ /Slope ₀

mV ₁₀ represents the measured instantaneous millivolt value of a point calibration standard solution,

PH ₁₀ represents the measured instantaneous pH value of a one-point calibration standard solution.

Stable conditions: start timing for 30s after pressing a point correction key, requirements:

①In the first 10s after 30s, the change of mV ₁₀ is less than 0.5mV. If it is established, record the last mV ₁₀ value and turn to a stable state. At this time, mV ₁ =mV ₁₀ .

mV ₁ represents the measured millivolt value of a one-point calibration standard solution.

②If the first 10s cannot be stabilized, then delay the judgment according to the above method, and write down the last mV ₁₀ value, at this time mV ₁ =mV ₁₀

③If it cannot be stabilized within 30″, an error message will be displayed

After stabilization, the single-chip microcomputer determines the final displayed PH ₁ value from the following formula according to the ambient temperature measured by the temperature sensor (that is, the temperature of the measured standard solution):

0°C～50°C PH ₁ =0.0000483t ₁ ² -0.001266t ₁ +4.004...(1)

50°C～60°C PH ₁ =0.0000483t ₁ ² -0.001266t ₁ +3.994...(2)

last store (PH ₁ , mV ₁ ); t ₁

PH ₁ represents the measured pH value of a one-point calibration standard solution,

t ₁ represents the ambient temperature value measured by one-point correction.

1.3. Two-point calibration

Sampling mV ₂₀ shows PH ₂₀ = PH ₀ -mV ₂₀ /Slope ₀

mV ₂₀ represents the measured instantaneous millivolt value of the two-point calibration standard solution,

PH ₂₀ represents the measured instantaneous pH value of the two-point calibration standard solution.

Stable conditions: start timing 30s after pressing the two-point correction key, requirements:

①In the first 10s after 30s, the change of mV ₂₀ is less than 0.5mV. If it is established, record the last mV ₂₀ value and turn to a stable state. At this time, mV ₂ =mV ₂₀

mV ₂ represents the measured millivolt value of the two-point calibration standard solution.

②If the first 10s cannot be stabilized, judge the delay according to the above method, and record the last mV ₁₀ value, at this time mV ₂ =mV ₂₀

③If it cannot be stabilized within 30″, an error message will be displayed

After stabilization, the single-chip microcomputer determines the final displayed PH ₂ value from the following formula according to the ambient temperature measured by the temperature sensor (that is, the temperature of the measured standard solution):

0°C～50°C PH ₂ =0.00006875t ₂ ² -0.006311t ₂ +6.979...(3)

50°C～60°C PH ₂ =0.0000776t ₂ ² -0.01268t ₂ +9.453...(4)

Store after stabilization (PH ₂ , mV ₂ ); t ₂

PH ₂ represents the measured pH value of the two-point calibration standard solution,

t ₂ represents the ambient temperature value measured by two-point calibration.

1.4. Calculate the slope

slope $\mathrm{Slope}=\frac{m{V}_2-\mathrm{<figure-callout\; id="1"\; label="m\; V"\; filenames="HDA00002162506500011.png,HDA00002162506500021.png"\; state="\{\{state\}\}">m</figure-callout>}{V}_{}{}_1}{{\mathrm{pH}}_2-{\mathrm{<figure-callout\; id="1"\; label="pH"\; filenames="HDA00002162506500011.png,HDA00002162506500021.png"\; state="\{\{state\}\}">pH</figure-callout>}}_1}$

The SLOPE value is required to be within the following range:

0.8×(0.19841t ₁ +54.195)<|SLOPE|<1.1×(0.19841t ₁ +54.195)

Otherwise an error is displayed.

Slope indicates the slope measured by the pH electrode.

1.5. Measurement

Sampling mV _x

mV _x0 represents the measured instantaneous millivolt value of the solution to be tested.

mV _x represents the measured millivolt value of the solution to be tested.

Stable conditions: start timing 30s after pressing the measurement key, requirements:

①In the first 10s after 30s, the change of mV _x0 is less than 0.5mV. If it is established, record the last value of mV _x0 and turn to a stable state. At this time, mV _x =mV _x0

②If the first 10s cannot be stabilized, judge the delay according to the above method, and record the final mV _x0 value, at this time mV _x =mV _x0

③If it cannot be stabilized within 30″, an error message will be displayed

Calculation: a) If t ₂ =t ₁ (the equal state remains equal for more than 0.5s)

$\mathrm{<span\; class="notranslate">\; Slope</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; m</span>}{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="m\; V"\; filenames="HDA00002162506500011.png,HDA00002162506500021.png"\; state="\{\{state\}\}">m</figure-callout></span><figure-callout\; id="1"\; label="m\; V"\; filenames="HDA00002162506500011.png,HDA00002162506500021.png"\; state="\{\{state\}\}">\; </figure-callout>}{\mathrm{<span\; class="notranslate">\; </span>}}_{}{\mathrm{<span\; class="notranslate">V</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; pH</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="pH"\; filenames="HDA00002162506500011.png,HDA00002162506500021.png"\; state="\{\{state\}\}">pH</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}$

${\mathrm{<span\; class="notranslate">\; pH</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="pH"\; filenames="HDA00002162506500011.png,HDA00002162506500021.png"\; state="\{\{state\}\}">pH</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; m</span>}{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="m\; V"\; filenames="HDA00002162506500011.png,HDA00002162506500021.png"\; state="\{\{state\}\}">m</figure-callout></span><figure-callout\; id="1"\; label="m\; V"\; filenames="HDA00002162506500011.png,HDA00002162506500021.png"\; state="\{\{state\}\}">\; </figure-callout>}{\mathrm{<span\; class="notranslate">\; </span>}}_{}{\mathrm{<span\; class="notranslate">V</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{\mathrm{<span\; class="notranslate">\; Slope</span>}}$

Finally the PH _x value is displayed.

PH _x represents the measured pH value of the solution to be tested

Note: If PH _x <0 or PH _x >14, an error message will be displayed

b) If t ₂ ≠t ₁

From t ₁ and t ₂ calculate PH _x from the following formula

$\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="mV"\; filenames="HDA00002162506500011.png,HDA00002162506500021.png"\; state="\{\{state\}\}">m</figure-callout></span><figure-callout\; id="1"\; label="mV"\; filenames="HDA00002162506500011.png,HDA00002162506500021.png"\; state="\{\{state\}\}">\; </figure-callout>}{\mathrm{<span\; class="notranslate">\; </span>}}_{}^{}{\mathrm{<span\; class="notranslate">V</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7.793</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="pH"\; filenames="HDA00002162506500011.png,HDA00002162506500021.png"\; state="\{\{state\}\}">pH</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 0.19841</span>}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="t"\; filenames="HDA00002162506500021.png"\; state="\{\{state\}\}">t</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 54.195</span>}<span\; class="notranslate">\; )</span>}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7.793</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; pH</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 0.19841</span>}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="t"\; filenames="HDA00002162506500011.png,HDA00002162506500021.png"\; state="\{\{state\}\}">t</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 54.195</span>}<span\; class="notranslate">\; )</span>}\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="m\; V"\; filenames="HDA00002162506500011.png,HDA00002162506500021.png"\; state="\{\{state\}\}">m</figure-callout></span><figure-callout\; id="1"\; label="m\; V"\; filenames="HDA00002162506500011.png,HDA00002162506500021.png"\; state="\{\{state\}\}">\; </figure-callout>}{\mathrm{<span\; class="notranslate">\; </span>}}_{}{\mathrm{<span\; class="notranslate">V</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}$

$\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="mV"\; filenames="HDA00002162506500021.png"\; state="\{\{state\}\}">m</figure-callout></span><figure-callout\; id="2"\; label="mV"\; filenames="HDA00002162506500021.png"\; state="\{\{state\}\}">\; </figure-callout>}{\mathrm{<span\; class="notranslate">\; </span>}}_{}^{}{\mathrm{<span\; class="notranslate">V</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7.793</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="pH"\; filenames="HDA00002162506500021.png"\; state="\{\{state\}\}">pH</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 0.19841</span>}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="t"\; filenames="HDA00002162506500021.png"\; state="\{\{state\}\}">t</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 54.195</span>}<span\; class="notranslate">\; )</span>}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7.793</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; pH</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 0.19841</span>}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="t"\; filenames="HDA00002162506500011.png,HDA00002162506500021.png"\; state="\{\{state\}\}">t</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 54.195</span>}<span\; class="notranslate">\; )</span>}\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="m\; V"\; filenames="HDA00002162506500021.png"\; state="\{\{state\}\}">m</figure-callout></span><figure-callout\; id="2"\; label="m\; V"\; filenames="HDA00002162506500021.png"\; state="\{\{state\}\}">\; </figure-callout>}{\mathrm{<span\; class="notranslate">\; </span>}}_{}{\mathrm{<span\; class="notranslate">V</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}$

${\mathrm{<span\; class="notranslate">\; Slope</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="m\; V"\; filenames="HDA00002162506500021.png"\; state="\{\{state\}\}">m</figure-callout></span><figure-callout\; id="2"\; label="m\; V"\; filenames="HDA00002162506500021.png"\; state="\{\{state\}\}">\; </figure-callout>}{\mathrm{<span\; class="notranslate">\; </span>}}_{}^{}{\mathrm{<span\; class="notranslate">V</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="m\; V"\; filenames="HDA00002162506500011.png,HDA00002162506500021.png"\; state="\{\{state\}\}">m</figure-callout></span><figure-callout\; id="1"\; label="m\; V"\; filenames="HDA00002162506500011.png,HDA00002162506500021.png"\; state="\{\{state\}\}">\; </figure-callout>}{\mathrm{<span\; class="notranslate">\; </span>}}_{}^{}{\mathrm{<span\; class="notranslate">V</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="P\; h"\; filenames="HDA00002162506500021.png"\; state="\{\{state\}\}">P</figure-callout></span><figure-callout\; id="2"\; label="P\; h"\; filenames="HDA00002162506500021.png"\; state="\{\{state\}\}">\; </figure-callout>}{\mathrm{<span\; class="notranslate">\; </span>}}_{}^{}{\mathrm{<span\; class="notranslate">h</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; \&prime;</span>}\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="P\; h"\; filenames="HDA00002162506500011.png,HDA00002162506500021.png"\; state="\{\{state\}\}">P</figure-callout></span><figure-callout\; id="1"\; label="P\; h"\; filenames="HDA00002162506500011.png,HDA00002162506500021.png"\; state="\{\{state\}\}">\; </figure-callout>}{\mathrm{<span\; class="notranslate">\; </span>}}_{}^{}{\mathrm{<span\; class="notranslate">h</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}$

${\mathrm{<span\; class="notranslate">\; pH</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="pH"\; filenames="HDA00002162506500011.png,HDA00002162506500021.png"\; state="\{\{state\}\}">pH</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; m</span>}{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="m\; V"\; filenames="HDA00002162506500011.png,HDA00002162506500021.png"\; state="\{\{state\}\}">m</figure-callout></span><figure-callout\; id="1"\; label="m\; V"\; filenames="HDA00002162506500011.png,HDA00002162506500021.png"\; state="\{\{state\}\}">\; </figure-callout>}{\mathrm{<span\; class="notranslate">\; </span>}}_{}^{}{\mathrm{<span\; class="notranslate">V</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}{{\mathrm{<span\; class="notranslate">\; Slope</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}$

1.6 Error indication

①Er ₁ : Standard seepage out of range

②Er ₂ : Two points of exudate and one point of exudate

③Er ₃ : 60s cannot be stabilized during calibration and measurement

④Er ₄ : PH measurement exceeds 0～14

mV measurement exceeds ±1999.9mV

⑤Er ₅ : Temperature exceeds (0～60°C) during calibration and measurement

⑥Er ₆ : Er ₆ electrode slope out of range

⑦Er ₇ : Er ₇ illegal operation

2. Automatic identification method of standard solution

Figure 3 is a schematic diagram of the scope of the pH value of the standard solution output by the patented pH electrode of the present invention. There are three commonly used standard solutions: PH=10, PH=6 and PH=4. According to the change of the ambient temperature, the range of the millivolt value of the solution measured by the pH electrode is as follows:

The range of millivolt value of standard solution with PH=10 is -156mV～-36mV;

The range of millivolt value of the standard solution with PH=6 is -20mV～100mV;

The millivolt value of the standard solution with PH=4 ranges from 150mV to 270mV;

Use the operational amplifier to amplify 5 times, and the single-chip microcomputer to collect, and judge the standard solution according to the millivolt value mVX of the collected standard solution:

-780mV≤mVX≤-180mV, which is the standard solution of PH=10;

-100mV≤mVX≤500mV, it is the standard solution of PH=6;

750mV≤mVX≤1375mV, which is the standard solution of PH=6;

The remaining ranges are treated as errors.

Claims (6)

1. A high-precision intelligent acidity meter comprises a single-chip microcomputer circuit, an A/D conversion circuit, a human-machine interface circuit and a power supply circuit, and the A/D conversion circuit and the human-machine interface circuit are connected with the single-chip microcomputer circuit respectively, and it is characterized in that A/D The D conversion circuit includes a temperature sensor, a pH sensor, a first operational amplifier, a second operational amplifier, a multi-channel analog switch and an A/D converter, and the outputs of the temperature sensor and the pH sensor are respectively connected to the multiple channel via the first and second operational amplifiers. A plurality of input terminals of one of the channels of the analog switch, the output terminal of one of the channels is connected to the A/D converter, and the output terminal of the other channel of the multi-channel analog switch is connected to the inverting input terminal of the second operational amplifier, Two of the input terminals of the other channel are respectively connected to resistors of different resistances for range switching, and the address terminals of the multi-channel analog switch are connected to the single-chip microcomputer circuit. 2. The high-precision intelligent acidity meter according to claim 1, wherein the signal output by the pH sensor is amplified by the second operational amplifier, and then connected to the X channel input terminals X0 and X1 of the multi-channel analog switch. 3. The high-precision intelligent acidity meter according to claim 1, characterized in that the signal output by the temperature sensor is amplified by the first operational amplifier, and then connected to the X channel input terminal X3 of the multi-channel analog switch. 4. The high-precision intelligent acidity meter as claimed in any one of claims 1 to 3, wherein the output terminal of the Y channel of the multi-channel analog switch is connected to the inverting input terminal of the second operational amplifier, and its input terminals Y0 and Y1 Connect resistors with different resistance values. 5. the measuring method of high-precision intelligent acidity meter as claimed in claim 1, it is characterized in that temperature compensation method, adopt temperature sensor to measure ambient temperature, the standard solution of non-standard temperature is corrected, single-chip microcomputer circuit adopts different according to different temperature ranges The formula is calculated to obtain the pH value of the standard solution at ambient temperature, and the specific method is as follows: When correcting by one point: 0

~50

50

~60

Wherein, PH ₁ represents the measured pH value of one-point calibration standard solution, and t ₁ represents the measured ambient temperature value of one-point calibration; During two-point calibration: 0

~50

50

~60 Wherein, PH ₂ represents the measured pH value of the two-point calibration standard solution, and t ₂ represents the measured ambient temperature value of the two-point calibration. 6. the measuring method of high-precision intelligent acidity meter as claimed in claim 5 is characterized in that when carrying out one-point correction and two-point correction, according to the millivolt value of the standard solution measured by the pH sensor, after being amplified by the operational amplifier, the single-chip microcomputer circuit Collect the amplified millivolt value, and automatically identify the standard solution according to the millivolt value range of different standard solutions.

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