Conductivity electrode calibration circuit and method for conductivity transmitter and storage medium

Abstract

The invention provides a conductivity electrode calibration circuit and method for a conductivity transmitter and a storage medium, and the calibration method comprises the steps: determining a voltage measurement value of a voltage output circuit, and determining the measurement resistance values of a plurality of calibration resistors in a resistance calibration circuit according to the voltage measurement value and the voltage amplitude of square waves, according to reference resistance values and measured resistance values of a plurality of calibration resistors, resistance calibration coefficients corresponding to the plurality of calibration resistors are determined, a measured conductivity value of a conductivity electrode is determined according to the calibration coefficients, and a conductivity calibration coefficient is determined according to the measured conductivity value and a reference conductivity value of reference liquid, so that automatic measurement and calibration are realized. And the conductivity measured by the conductivity electrode under the actual condition can be calibrated through the conductivity calibration coefficient, so that the tedious process of manual operation is avoided, and the accuracy and the efficiency can be improved.

Description

Technical Field

[0001] This application relates to the field of electronic circuits, and more particularly to a conductivity electrode calibration circuit, method, and storage medium for a conductivity transmitter. Background Technology

[0002] Currently, EC (conductivity) transmitters must be calibrated in order to accurately measure the conductivity of the conductivity cell. The calibration process typically involves manually suspending the EC electrode and immersing it in a standard conductivity solution, then manually inputting the measured ADC voltage value into the corresponding register for further calibration. Therefore, the calibration process requires a significant amount of manual operation, increasing the probability of errors and extending the calibration time. Summary of the Invention

[0003] This application provides a conductivity electrode calibration circuit, method, and storage medium for a conductivity transmitter to solve at least one problem in the related art. The technical solution is as follows:

[0004] In a first aspect, embodiments of this application provide a conductivity electrode calibration circuit for a conductivity transmitter, comprising:

[0005] Square wave generator module, used to output square waves;

[0006] The calibration module includes a resistance calibration circuit, a conductivity cell, a voltage output circuit, and a conductivity electrode placed in a reference solution within the conductivity cell. The resistance calibration circuit is connected to the square wave generator module, the conductivity electrode, and the voltage output circuit.

[0007] The controller stores the reference resistance values ​​of several calibration resistors in the resistance calibration circuit and the reference conductivity value of the reference liquid, which are used to determine the voltage measurement value of the voltage output circuit; based on the voltage measurement value and the voltage amplitude of the square wave, it determines the measured resistance value of several calibration resistors; based on the reference resistance values ​​and the measured resistance values ​​of several calibration resistors, it determines the resistance calibration coefficients corresponding to several calibration resistors; based on the calibration coefficients, it determines the measured conductivity value of the conductivity electrode; and based on the measured conductivity value and the reference conductivity value, it determines the conductivity calibration coefficient.

[0008] In one embodiment, the resistance calibration circuit includes a first analog switch, a second analog switch, a third analog switch, a first resistor, a second resistor, and a third resistor; the first analog switch is connected to the second analog switch and the third analog switch, the second analog switch is connected to the conductivity electrode and the first resistor, the first resistor is connected to the voltage output circuit, the second resistor is connected to the third analog switch and the voltage output circuit, and the third resistor is connected in parallel with the second resistor.

[0009] The controller controls the level states of the control pins of the first analog switch, the second analog switch, and the third analog switch, and the first resistor, the second resistor, and the third resistor constitute a number of calibration resistors.

[0010] Secondly, embodiments of this application provide a calibration method, including:

[0011] Determine the voltage measurement value of the voltage output circuit, and based on the voltage measurement value and the voltage amplitude of the square wave, determine the measurement resistance value of several calibration resistors in the resistance calibration circuit.

[0012] Based on the reference resistance values ​​and measured resistance values ​​of several calibration resistors, determine the resistance calibration coefficients corresponding to several calibration resistors.

[0013] The measured conductivity value of the conductivity electrode is determined based on the calibration coefficient.

[0014] The conductivity calibration coefficient is determined based on the measured conductivity value and the reference conductivity value of the reference solution.

[0015] In one embodiment, determining the measured resistance values ​​of a plurality of calibration resistors in the resistance calibration circuit based on the measured voltage value and the voltage amplitude of the square wave includes:

[0016] The measurement current is determined based on the voltage measurement value and the feedback resistor in the voltage output circuit;

[0017] The operating state of the control resistor calibration circuit is determined based on the voltage amplitude and the measured current, and the measured resistance value corresponding to each equivalent calibration resistor in the resistor calibration circuit is determined under different operating states.

[0018] In one embodiment, the operating states of the control resistor calibration circuit include:

[0019] The calibration procedure is initiated by triggering a command;

[0020] The operating state of the automatic control resistor calibration circuit changes in a preset sequence, entering different operating states according to the preset sequence.

[0021] In one embodiment, determining the resistance calibration coefficients corresponding to the plurality of calibration resistors based on the reference resistance values ​​and measured resistance values ​​of the plurality of calibration resistors includes:

[0022] The resistance calibration coefficient corresponding to the first calibration resistor is determined based on the ratio of the reference resistance value to the corresponding measured resistance value of the first calibration resistor under the first working state.

[0023] The resistance calibration coefficient corresponding to the second calibration resistor is determined based on the ratio of the reference resistance value to the corresponding measured resistance value of the second calibration resistor under the second working state; the first calibration resistor is greater than the second calibration resistor.

[0024] In one embodiment, determining the measured conductivity value of the conductivity electrode based on the calibration coefficient includes:

[0025] The control resistor calibration circuit operates in the third operating state, determining the conductivity cell resistance value based on the voltage amplitude and the measured current.

[0026] When the resistance value of the conductivity cell is greater than the measured resistance value corresponding to the first calibration resistor, the calibration resistance value of the conductivity cell is determined according to the first product of the resistance calibration coefficient corresponding to the first calibration resistor and the resistance value of the conductivity cell.

[0027] When the resistance value of the conductivity cell is less than or equal to the measured resistance value corresponding to the first calibration resistor, the calibration resistance value of the conductivity cell is determined based on the resistance calibration coefficient corresponding to the first calibration resistor, the resistance calibration coefficient corresponding to the second calibration resistor, the resistance value of the conductivity cell, the measured resistance value corresponding to the first calibration resistor, and the measured resistance value corresponding to the second calibration resistor.

[0028] The measured conductivity value of the conductivity electrode is determined based on the calibration resistance value of the conductivity cell.

[0029] In one embodiment, when the conductivity cell resistance value is less than or equal to the measured resistance value corresponding to the first calibration resistor, determining the calibration resistance value of the conductivity cell based on the resistance calibration coefficient corresponding to the first calibration resistor, the resistance calibration coefficient corresponding to the second calibration resistor, the conductivity cell resistance value, the measured resistance value corresponding to the first calibration resistor, and the measured resistance value corresponding to the second calibration resistor includes:

[0030] When the resistance value of the conductivity cell is less than or equal to the measured resistance value corresponding to the first calibration resistor, determine the first difference between the resistance calibration coefficient corresponding to the second calibration resistor and the resistance calibration coefficient corresponding to the first calibration resistor.

[0031] Determine the second difference between the conductivity cell resistance value and the measured resistance value corresponding to the first calibration resistor, and the third difference between the measured resistance value corresponding to the second calibration resistor and the measured resistance value corresponding to the first calibration resistor;

[0032] Determine the ratio of the difference between the second difference and the third difference to the second product of the first difference, and obtain the target calibration coefficient based on the sum of the second product and the resistance calibration coefficient corresponding to the first calibration resistor;

[0033] The calibration resistance value of the conductivity cell is determined by the third product of the target calibration coefficient and the conductivity cell resistance value.

[0034] In one embodiment, determining the conductivity calibration coefficient based on the measured conductivity value and the reference conductivity value of the reference liquid includes:

[0035] The conductivity calibration coefficient is determined based on the ratio of the reference conductivity value of the reference solution to the measured conductivity value.

[0036] Thirdly, embodiments of this application provide a readable storage medium storing a program that, when executed, implements the method in any of the above-described embodiments.

[0037] The beneficial effects of the above technical solution include at least the following:

[0038] By determining the voltage measurement value of the voltage output circuit, and based on the voltage measurement value and the voltage amplitude of the square wave, the measured resistance value of several calibration resistors in the resistance calibration circuit is determined. Based on the reference resistance value and the measured resistance value of the several calibration resistors, the corresponding resistance calibration coefficients of the several calibration resistors are determined. Based on the calibration coefficients, the measured conductivity value of the conductivity electrode is determined. Based on the measured conductivity value and the reference conductivity value of the reference liquid, the conductivity calibration coefficient is determined, thus realizing automatic measurement and calibration. The conductivity calibration coefficient can be used to calibrate the conductivity of the conductivity electrode measured under actual conditions, avoiding the cumbersome process of manual operation and improving accuracy and efficiency.

[0039] The above overview is for illustrative purposes only and is not intended to be limiting in any way. In addition to the illustrative aspects, embodiments, and features described above, these aspects, embodiments, and features will become readily apparent from the accompanying drawings and the following detailed description. Attached Figure Description

[0040] In the accompanying drawings, unless otherwise specified, the same reference numerals throughout the various drawings denote the same or similar parts or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings depict only some embodiments disclosed in this application and should not be construed as limiting the scope of this application.

[0041] Figure 1 This is a schematic diagram of a conductivity electrode calibration circuit for a conductivity transmitter according to an embodiment of this application;

[0042] Figure 2 This is a schematic diagram of a resistor calibration circuit in the zero operating state according to an embodiment of this application;

[0043] Figure 3 This is a schematic diagram of a resistor calibration circuit in the first operating state according to an embodiment of this application;

[0044] Figure 4This is a schematic diagram of a resistor calibration circuit in the second operating state according to an embodiment of this application;

[0045] Figure 5 This is a schematic diagram of a resistor calibration circuit in a third operating state according to an embodiment of this application;

[0046] Figure 6 This is a schematic flowchart illustrating the steps of a calibration method according to an embodiment of this application.

[0047] 1. Square wave generator module; 11. Square wave generator; 2. Calibration module; 21. Conductivity cell; 22. Resistance calibration circuit; 23. Voltage output circuit. Detailed Implementation

[0048] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of this application. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0049] Reference Figure 1 This application provides a conductivity electrode calibration circuit for a conductivity transmitter, comprising:

[0050] Square wave generator module 1 is used to output square waves.

[0051] The calibration module 2 includes a resistance calibration circuit 22, a conductivity cell 21, a voltage output circuit 23, and a conductivity electrode placed in the reference liquid in the conductivity cell 21. The resistance calibration circuit 22 is connected to the square wave generation module 1, the conductivity electrode, and the voltage output circuit 23.

[0052] The controller (not shown) stores the reference resistance values ​​of several calibration resistors in the resistance calibration circuit 22 and the reference conductivity value of the reference liquid, which is used to determine the voltage measurement value of the voltage output circuit 23; based on the voltage measurement value and the voltage amplitude of the square wave, it determines the measured resistance value of several calibration resistors; based on the reference resistance values ​​and the measured resistance values ​​of several calibration resistors, it determines the resistance calibration coefficients corresponding to several calibration resistors; based on the calibration coefficients, it determines the measured conductivity value of the conductivity electrode; and based on the measured conductivity value and the reference conductivity value, it determines the conductivity calibration coefficient.

[0053] Optionally, the square wave generation module 1 includes a square wave generator 11 and an inverse proportional amplifier. The inverse proportional amplifier includes a capacitor C139, resistors R35 and R40, and a precision operational amplifier U26. The square wave generator 11 is used to generate a square wave with a frequency of + / -2.4V and a frequency of 1.5kHz. After passing through the inverse proportional amplifier, the square wave output by the square wave generation module 1 is a square wave with a frequency of + / -0.6V and a frequency of 1.5kHz. Output = Input × (R35 / R40) = + / -2.4V × 7.5KΩ / 30KΩ = + / -0.6V, that is, the voltage amplitude of the square wave is + / -0.6V.

[0054] Optionally, the calibration module 2 includes a conductivity cell 21, a resistance calibration circuit 22, a voltage output circuit 23, and conductivity electrodes (EC2+, EC2-) placed in the reference solution in the conductivity cell 21. The resistance calibration circuit 22 is connected to the square wave generating module 1, the conductivity electrodes, and the voltage output circuit 23.

[0055] Optionally, the calibration circuit includes a 100Ω protection resistor R66, a 650Ω first resistor (150Ω first sub-resistor R52 + 560Ω second sub-resistor R53), a 560Ω second resistor R64, a 560Ω third resistor R68, a first analog switch U22, a second analog switch U23, and a third analog switch U24. The first analog switch U22 is connected to the second analog switch U23 and the third analog switch U24. The second analog switch U23 is connected to the conductivity electrode and the first resistor. The first resistor is connected to the voltage output circuit 23. The second resistor R64 is connected to the third analog switch U23 and the voltage output circuit 23. The third resistor R68 is connected in parallel with the second resistor R64. The resistance of each analog switch is extremely low and can be ignored.

[0056] Among them, the control pins (pin 6 / IN pin) of the first analog switch U22, the second analog switch U23, and the third analog switch U24 are connected to the controller. The controller controls the level state of the control pins (pin 6 / IN pin) of the first analog switch U22, the second analog switch U23, and the third analog switch U24. Several calibration resistors are formed by the first resistor, the second resistor R64, and the third resistor R68.

[0057] In this embodiment, the controller can control the level state of the control pins (pin 6 / IN pin) of the first analog switch U22, the second analog switch U23, and the third analog switch U24, thereby enabling the resistor calibration circuit 22 to switch between different "levels" (operating states). Specifically, the common pin is pin 4 / COM, the normally open pin is pin 1 / NO, and the normally closed pin is pin 3 / NC.

[0058] like Figure 2As shown, in the zero working state, the resistance calibration circuit 22 is used to calibrate the no-load value: the control pin of the first analog switch U22 is at a high level, the common pin COM of the first analog switch U22 will be connected to the normally open pin NO, the normally open pin NO is floating, so the corresponding zero calibration resistor is infinite.

[0059] like Figure 3 As shown, in the first working state, the resistance calibration circuit 22 is used to calibrate the first calibration resistor: the control pin of the first analog switch U22 is controlled to be low, and the common pin COM of the first analog switch U22 will be connected to the normally closed pin NC; the control pin of the second analog switch U23 is controlled to be high, and the common pin COM of the second analog switch U23 will be connected to the normally open pin NO; the control pin of the third analog switch U29 is controlled to be low, and the common pin COM of the third analog switch U29 will be connected to the normally closed pin NC. At this time, the reference resistance value of the first calibration resistor in the first working state is: the first resistor (150Ω first sub-resistance R52 + 560Ω second sub-resistance R53), that is, 710Ω.

[0060] like Figure 4 As shown, in the second working state, the resistance calibration circuit 22 is used to calibrate the second calibration resistor: when the control pin of the first analog switch U22 is at a low level, the common pin COM of the first analog switch U22 will be connected to the normally closed pin NC; when the control pin of the second analog switch U23 is at a high level, the common pin COM of the second analog switch U23 will be connected to the normally open pin NO; when the control pin of the third analog switch U29 is at a high level, the common pin COM of the third analog switch U29 will be connected to the normally open pin NO. At this time, the reference resistance value of the second calibration resistor in the second working state is the parallel resistance of R64, R68, R52+R53, which is 560Ω / / 560Ω / / 710Ω(150Ω+560Ω)=200.808Ω.

[0061] like Figure 5 As shown, in the third working state, the resistance calibration circuit 22 is used to calibrate the conductivity cell 21 and determine the resistance value of the conductivity cell 21: the control pin of the first analog switch U22 is controlled to be low, and the common pin COM of the first analog switch U22 will be connected to the normally closed pin NC; the control pin of the second analog switch U23 is controlled to be low, and the common pin COM of the second analog switch U23 will be connected to the normally closed pin NC; the control pin of the third analog switch U29 is controlled to be low, and the common pin COM of the third analog switch U29 will be connected to the normally closed pin NC.

[0062] like Figure 1As shown, the voltage output circuit 23 is a current-to-voltage conversion circuit, including capacitor C138, feedback resistor R46, and operational amplifier U17D. The output Vout of operational amplifier U17D is connected to the ADC acquisition pin of the controller, so the controller can obtain the voltage measurement value of voltage output circuit 23, i.e., the magnitude of Vout. Since operational amplifier U17D and feedback resistor R46 form a negative feedback system, pins 12 (+) and 13 (-) form a virtual short. Pin 12 (+) is connected to GND, so pin 13 (+) is 0V. Since the left side of R66 is +0.6V and pin 13 (-) is 0V, R66 and the equivalent resistance determined by the resistance calibration circuit 22 under different states (such as the first calibration resistor, the second calibration resistor, or the second calibration resistor, etc.) are all in series.

[0063] It should be noted that, Figure 1 The models, sizes, and reference solutions of the capacitors, resistors, and electronic components listed in this application are merely examples for illustrative purposes and do not constitute a limitation of this solution. They can be set according to actual needs. The resistance error in this application is 0.1%. For example, in this application, the conductivity cell 21 contains a reference solution (standard solution) of 1408 μS / cm, corresponding to a resistance of 710 Ω. Therefore, this application constructs the closest resistance value of 710.227 Ω (considering resistance error) by setting a first sub-resistor R52 of 150 Ω and a second sub-resistor R53 of 560 Ω to approximate 710 Ω. Since the conductivity range required by this application is 0-5000 Us / cm, and the resistance corresponding to 5000 Us / cm is 200 Ω, the closest resistance value of 200.808 Ω (considering resistance error) is obtained by using the existing combination of resistors R64, R68, and R52+R53 to approximate 200 Ω. Therefore, it is understandable that if an approximation of 300Ω, 500Ω, etc., is required, the specific size of each resistor can be adjusted based on the required approximate value. The resistor sizes shown in this application are examples listed in the requirements of this application and do not constitute a limitation. When higher accuracy is required, more calibration resistors can be designed. Furthermore, this application uses two calibration resistors of 710Ω and 200.808Ω as examples. In other embodiments, the number of "levels" or operating states set to determine the number of calibration resistors based on accuracy requirements can be set according to actual needs.

[0064] Optionally, the controller may be composed of any one or more processor chips, including but not limited to MCU microcontroller, FPGA, CPLD, DSP, ARM, etc.; the controller's register may store the reference resistance values ​​of several calibration resistors in advance, such as the reference resistance value of the first calibration resistor, the reference resistance value of the second calibration resistor, and the reference conductivity value of the current reference liquid, 1408us / cm.

[0065] Reference Figure 6 The flowchart illustrates a calibration method according to an embodiment of this application. This calibration method can be executed by a controller and may include at least steps S100-S400:

[0066] S100. Determine the voltage measurement value of the voltage output circuit 23, and based on the voltage measurement value and the voltage amplitude of the square wave, determine the measurement resistance value of several calibration resistors in the resistance calibration circuit 22.

[0067] S200. Based on the reference resistance values ​​and measured resistance values ​​of several calibration resistors, determine the resistance calibration coefficients corresponding to several calibration resistors.

[0068] S300. Determine the measured conductivity value of the conductivity electrode based on the calibration coefficient.

[0069] S400. Determine the conductivity calibration coefficient based on the measured conductivity value and the reference conductivity value of the reference liquid.

[0070] The technical solution of this application embodiment determines the voltage measurement value of the voltage output circuit 23, and determines the measured resistance value of a plurality of calibration resistors in the resistance calibration circuit 22 based on the voltage measurement value and the voltage amplitude of the square wave. Based on the reference resistance value and the measured resistance value of the plurality of calibration resistors, the resistance calibration coefficient corresponding to the plurality of calibration resistors is determined. Based on the calibration coefficient, the measured conductivity value of the conductivity electrode is determined. Based on the measured conductivity value and the reference conductivity value of the reference liquid, the conductivity calibration coefficient is determined, thereby realizing automatic measurement and calibration. The conductivity calibration coefficient can be used to calibrate the conductivity of the conductivity electrode measured under actual conditions, avoiding the cumbersome process of manual operation and improving accuracy and efficiency.

[0071] In one embodiment, in step S100, the controller can obtain the voltage measurement value of the voltage output circuit 23, i.e., the output Vout of the operational amplifier U17D, through its ADC pin.

[0072] In one embodiment, step S100 determines the measured resistance values ​​of several calibration resistors in the resistance calibration circuit 22 based on the measured voltage value and the voltage amplitude of the square wave, including steps S110-S130:

[0073] S110. Determine the measuring current based on the voltage measurement value and the feedback resistor in the voltage output circuit 23.

[0074] It should be noted that since the protection resistor R66 and the equivalent resistance determined by the resistance calibration circuit 22 under different states (such as the first calibration resistor, the second calibration resistor, or the second calibration resistor, etc.) are all in series, and the current will flow through the feedback resistor R46, the voltage measurement value Vout = -I(R66) × R46. Therefore, the specific value of the measurement current I(R66) can be calculated based on this formula.

[0075] S120: Control the working state of the resistance calibration circuit 22, and determine the measured resistance value corresponding to each equivalent calibration resistor in the resistance calibration circuit 22 under different working states based on the voltage amplitude and the measured current.

[0076] Optionally, the controller in this embodiment of the application generates a trigger command either by itself or through external hardware, such as a touchscreen or a button, to initiate the calibration program. When the calibration program is initiated, the controller automatically controls the operating state of the resistance calibration circuit 22 to change in a preset order, entering different operating states according to the preset sequence. For example, the sequence can be set to zero, first, second, and third operating states, or first, second, and third operating states, etc., and the controller can record the corresponding test results in each operating state, such as the zero, first, and second calibration resistances and the resistance value of the conductivity cell 21.

[0077] In this embodiment, since the protection resistor R66 is known to be 100Ω and the voltage amplitude of the square wave input to the left side of the protection resistor R66 is + / -0.6V, the measured resistance value corresponding to each equivalent calibration resistor in the resistance calibration circuit 22 can be determined under different operating conditions by subtracting the ratio of the voltage amplitude of + / -0.6V to the measured current I (R66) from the value of R66 (100Ω). For example, in the zeroth operating state, since the measured current I(R66) is 0, the measured resistance value is infinite. However, due to the certain accuracy range of each electronic component in the overall circuit, the input offset voltage Vos and input bias current Ib of the operational amplifier, and the parasitic inductance and capacitance of the circuit board traces, the calculation results may be affected, causing the measured resistance value to be inconsistent with the reference resistance value. For example, in the first operating state, the measured resistance value corresponding to the first calibration resistor 710Ω may be 680Ω; in the second operating state, the measured resistance value corresponding to the second calibration resistor 200.808Ω may be 190Ω; in the third operating state, the resistance value of the conductivity cell 21 can be measured. For ease of explanation, the following process is illustrated with examples of 680Ω and 190Ω.

[0078] In one implementation, step S200 includes steps S210-S220:

[0079] S210. Determine the resistance calibration coefficient corresponding to the first calibration resistor based on the ratio of the reference resistance value to the corresponding measured resistance value of the first calibration resistor under the first working state.

[0080] For example, based on the ratio of the reference resistance value of the first calibration resistor (710Ω) to the corresponding measured resistance value (680Ω) in the first working state (710 / 680 = 1.04411764705882), the resistance calibration coefficient K1 corresponding to the first calibration resistor is 1.04411764705882.

[0081] S220. Determine the resistance calibration coefficient corresponding to the second calibration resistor based on the ratio of the reference resistance value to the corresponding measured resistance value of the second calibration resistor under the second working state.

[0082] In this embodiment of the application, the first calibration resistor 710 is greater than the second calibration resistor 200.808Ω. Based on the ratio of the reference resistance value 200.808Ω to the corresponding measured resistance value 190Ω of the second calibration resistor in the second working state, 200.808 / 190, the resistance calibration coefficient K2 corresponding to the second calibration resistor is determined to be 1.05688421052632.

[0083] It should be noted that K1 and K2 are also stored in the processor's registers. In some implementations, K1 and the reference resistance value of the first calibration resistor can be stored in register R1, and K2 and the reference resistance value of the second calibration resistor can be stored in register R2. That is, they are stored in different registers. When the controller is powered on each time, it can directly read the data from the registers for subsequent calibration calculations.

[0084] In one implementation, step S300 includes steps S310-S340:

[0085] S310, the control resistor calibration circuit 22 is in the third working state, and the resistance value of the conductivity cell 21 is determined according to the voltage amplitude and the measured current.

[0086] Similarly, the control resistor calibration circuit 22 operates in the third operating state. At this time, based on the ratio of the voltage amplitude value of + / -0.6V to the measurement current I (R66), and subtracting the value of R66 (100Ω), the resistance value of the conductivity cell 21 can be determined and denoted as Rx.

[0087] S320. When the resistance value of conductivity cell 21 is greater than the measured resistance value corresponding to the first calibration resistor, the calibration resistance value of conductivity cell 21 is determined according to the first product of the resistance calibration coefficient corresponding to the first calibration resistor and the resistance value of conductivity cell 21.

[0088] For example, when the resistance value Rx of conductivity cell 21 is greater than the measured resistance value of 680Ω corresponding to the first calibration resistor, since the conductivity corresponding to 710Ω-∞Ω is 1408 -0us / cm, the accuracy of resistance measurement is relatively low. In this case, the target calibration coefficient K corresponding to the resistance value of conductivity cell 21 is taken as K1. Then, the calibration resistance value Rcal of conductivity cell 21 can be determined according to the first product of the resistance calibration coefficient K1 corresponding to the first calibration resistor and the resistance value Rx of conductivity cell 21.

[0089] S330. When the resistance value of the conductivity cell 21 is less than or equal to the measured resistance value corresponding to the first calibration resistor, the calibration resistance value of the conductivity cell 21 is determined according to the resistance calibration coefficient corresponding to the first calibration resistor, the resistance calibration coefficient corresponding to the second calibration resistor, the resistance value of the conductivity cell 21, the measured resistance value corresponding to the first calibration resistor, and the measured resistance value corresponding to the second calibration resistor.

[0090] Optionally, S330 includes S3301-S3304:

[0091] S3301. When the resistance value of the conductivity cell 21 is less than or equal to the measured resistance value corresponding to the first calibration resistor, determine the first difference between the resistance calibration coefficient corresponding to the second calibration resistor and the resistance calibration coefficient corresponding to the first calibration resistor.

[0092] For example, when the resistance value Rx of conductivity cell 21 is less than or equal to the measured resistance value of 680Ω corresponding to the first calibration resistor, the target calibration coefficient K needs to be calculated proportionally. Specifically, the first difference K2-K1 between the resistance calibration coefficient K2 corresponding to the second calibration resistor and the resistance calibration coefficient K1 corresponding to the first calibration resistor is determined and denoted as K3.

[0093] S3302, Determine the second difference between the resistance value of the conductivity cell 21 and the measured resistance value corresponding to the first calibration resistor, and the third difference between the measured resistance value corresponding to the second calibration resistor and the measured resistance value corresponding to the first calibration resistor.

[0094] Optionally, a second difference (Rx-680Ω) between the resistance value Rx of the conductivity cell 21 and the measured resistance value 680Ω corresponding to the first calibration resistor is determined, and a third difference (190Ω-680Ω) between the measured resistance value 190Ω corresponding to the second calibration resistor and the measured resistance value 680Ω corresponding to the first calibration resistor is determined.

[0095] S3303. Determine the ratio of the difference between the second difference and the third difference to the second product of the first difference, and obtain the target calibration coefficient based on the sum of the second product and the resistance calibration coefficient corresponding to the first calibration resistor.

[0096] Optionally, the ratio of the difference between the second difference (Rx-680Ω) and the third difference (190Ω-680Ω) is determined as (Rx-680Ω) / (190Ω-680Ω), and the second product of this ratio and the first difference K3 is calculated as: K3×(Rx-680Ω) / (190Ω-680Ω). The target calibration coefficient K is then obtained by summing the second product with the resistance calibration coefficient K1 corresponding to the first calibration resistor.

[0097] K=K1+K3×(Rx-680Ω) / (190Ω-680Ω)

[0098] S3304. Determine the calibration resistance value of the conductivity cell 21 based on the third product of the target calibration coefficient and the resistance value of the conductivity cell 21.

[0099] Finally, based on the third product of the target calibration coefficient K and the resistance value Rx of the conductivity cell 21, the calibration resistance value Rcal of the conductivity cell 21 is determined to be Rx × K.

[0100] S340. Determine the measured conductivity value of the conductivity electrode based on the calibration resistance value of the conductivity cell 21.

[0101] It should be noted that after obtaining the calibration resistance value Rcal of the conductivity cell 21, which is the approved resistance value, the calculation of the conductivity value of the conductivity electrode based on the calibration resistance value Rcal (denoted as the measured conductivity value) is existing technology and will not be elaborated further.

[0102] It should be noted that due to manufacturing processes, the measured conductivity value of each conductivity electrode will have a certain error. The standard 1.0 conductivity electrode coefficient is 1.0, so the measured value of a 1408 Us / cm standard solution is 1408 Us / cm. If, due to process errors, the measured value of this electrode is 1388 Us / cm, then the conductivity electrode coefficient of this electrode becomes 1408 / 1388 = 1.014409. Therefore, it is necessary to determine the conductivity calibration coefficient. Adjusting the conductivity electrode coefficient is equivalent to calibrating the measured conductivity value of 1388 to 1408.

[0103] In one embodiment, in step S400, specifically, a conductivity calibration coefficient is determined based on the ratio of the reference conductivity value of the reference solution to the measured conductivity value. Therefore, when subsequently measuring the conductivity of different solutions, the controller can determine the calibrated target conductivity value based on the product of the actual measured conductivity value and the conductivity calibration coefficient, thereby achieving automatic calibration of the conductivity electrode.

[0104] In this embodiment, by designing a conductivity electrode calibration circuit for a conductivity transmitter, personnel can execute the calibration program through the controller's human-machine interface or button operation, thereby controlling the resistance calibration circuit 22 and achieving automatic "gear switching" (working state). This allows for the determination of the resistance calibration coefficient and conductivity calibration coefficient corresponding to different calibration resistors, automatically achieving calibration and ensuring the linear accuracy of the calibration resistance value and target conductivity value. This greatly saves most of the time lost by manual operation and reduces the error rate caused by manual operation.

[0105] This application provides a readable storage medium storing a program that can be executed by the aforementioned controller (also known as a processor). When the program is executed by the processor, it implements the calibration method provided in the above embodiments.

[0106] In the above embodiments, implementation can be achieved, in whole or in part, through software, hardware, firmware, or any combination thereof. When implemented in software, it can be implemented, in whole or in part, as a program product. A program product includes one or more computer instructions.

[0107] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of those different embodiments or examples.

[0108] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly specified.

[0109] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process. Furthermore, the scope of the preferred embodiments of this application includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functionality involved.

[0110] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus or device (such as a computer-based system, a processor-included system or other system that can fetch and execute instructions from, an instruction execution system, apparatus or device).

[0111] It should be understood that various parts of this application can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented using software or firmware stored in memory and executed by a suitable instruction execution system. All or part of the steps of the methods in the above embodiments can be implemented by a program instructing related hardware, the program being stored in a readable storage medium, and when executed, the program includes one or a combination of the steps of the method embodiments.

[0112] Furthermore, the functional units in the various embodiments of this application can be integrated into a processing module, or each unit can exist physically separately, or two or more units can be integrated into a module. The integrated module can be implemented in hardware or as a software functional module. If the integrated module is implemented as a software functional module and sold or used as an independent product, it can also be stored in a readable storage medium. This storage medium can be a read-only memory, a disk, or an optical disk, etc.

[0113] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various variations or substitutions within the technical scope disclosed in this application, and these should all be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A conductivity electrode calibration circuit for a conductivity transmitter, characterized in that, include: Square wave generator module, used to output square waves; The calibration module includes a resistance calibration circuit, a conductivity cell, a voltage output circuit, and a conductivity electrode placed in a reference solution within the conductivity cell. The resistance calibration circuit is connected to the square wave generator module, the conductivity electrode, and the voltage output circuit. The controller stores the reference resistance values ​​of several calibration resistors in the resistance calibration circuit and the reference conductivity value of the reference liquid, which are used to determine the voltage measurement value of the voltage output circuit. Based on the voltage measurement value and the voltage amplitude of the square wave, determine the measured resistance value of several calibration resistors. Based on the reference resistance value and the measured resistance value of several calibration resistors, determine the resistance calibration coefficient corresponding to several calibration resistors. Based on the calibration coefficient, the measured conductivity value of the conductivity electrode is determined, and based on the measured conductivity value and the reference conductivity value, the conductivity calibration coefficient is determined.

2. The conductivity electrode calibration circuit for a conductivity transmitter according to claim 1, characterized in that: The resistance calibration circuit includes a first analog switch, a second analog switch, a third analog switch, a first resistor, a second resistor, and a third resistor; the first analog switch is connected to the second analog switch and the third analog switch, the second analog switch is connected to the conductivity electrode and the first resistor, the first resistor is connected to the voltage output circuit, the second resistor is connected to the third analog switch and the voltage output circuit, and the third resistor is connected in parallel with the second resistor. The controller controls the level states of the control pins of the first analog switch, the second analog switch, and the third analog switch, and the first resistor, the second resistor, and the third resistor constitute a number of calibration resistors.

3. A calibration method, characterized in that, Applications include conductivity electrode calibration circuits for conductivity transmitters, including: Determine the voltage measurement value of the voltage output circuit, and based on the voltage measurement value and the voltage amplitude of the square wave, determine the measurement resistance value of several calibration resistors in the resistance calibration circuit. Based on the reference resistance values ​​and measured resistance values ​​of several calibration resistors, determine the resistance calibration coefficients corresponding to several calibration resistors. The measured conductivity value of the conductivity electrode is determined based on the calibration coefficient. The conductivity calibration coefficient is determined based on the measured conductivity value and the reference conductivity value of the reference solution.

4. The calibration method according to claim 3, characterized in that: The process of determining the measured resistance values ​​of several calibration resistors in the resistance calibration circuit based on the measured voltage value and the voltage amplitude of the square wave includes: The measurement current is determined based on the voltage measurement value and the feedback resistor in the voltage output circuit; The operating state of the control resistor calibration circuit is determined based on the voltage amplitude and the measured current, and the measured resistance value corresponding to each equivalent calibration resistor in the resistor calibration circuit is determined under different operating states.

5. The calibration method according to claim 4, characterized in that: The operating states of the control resistor calibration circuit include: The calibration procedure is initiated by triggering a command; The operating state of the automatic control resistor calibration circuit changes in a preset sequence, entering different operating states according to the preset sequence.

6. The calibration method according to claim 4, characterized in that: The step of determining the resistance calibration coefficients corresponding to several calibration resistors based on the reference resistance values ​​and measured resistance values ​​of several calibration resistors includes: The resistance calibration coefficient corresponding to the first calibration resistor is determined based on the ratio of the reference resistance value to the corresponding measured resistance value of the first calibration resistor under the first working state. The resistance calibration coefficient corresponding to the second calibration resistor is determined based on the ratio of the reference resistance value to the corresponding measured resistance value of the second calibration resistor under the second working state; the first calibration resistor is greater than the second calibration resistor.

7. The calibration method according to claim 6, characterized in that: The process of determining the measured conductivity value of the conductivity electrode based on the calibration coefficient includes: The control resistor calibration circuit operates in the third operating state, determining the conductivity cell resistance value based on the voltage amplitude and the measured current. When the resistance value of the conductivity cell is greater than the measured resistance value corresponding to the first calibration resistor, the calibration resistance value of the conductivity cell is determined according to the first product of the resistance calibration coefficient corresponding to the first calibration resistor and the resistance value of the conductivity cell. When the resistance value of the conductivity cell is less than or equal to the measured resistance value corresponding to the first calibration resistor, the calibration resistance value of the conductivity cell is determined based on the resistance calibration coefficient corresponding to the first calibration resistor, the resistance calibration coefficient corresponding to the second calibration resistor, the resistance value of the conductivity cell, the measured resistance value corresponding to the first calibration resistor, and the measured resistance value corresponding to the second calibration resistor. The measured conductivity value of the conductivity electrode is determined based on the calibration resistance value of the conductivity cell.

8. The calibration method according to claim 7, characterized in that: When the conductivity cell resistance value is less than or equal to the measured resistance value corresponding to the first calibration resistor, the calibration resistance value of the conductivity cell is determined based on the resistance calibration coefficient corresponding to the first calibration resistor, the resistance calibration coefficient corresponding to the second calibration resistor, the conductivity cell resistance value, the measured resistance value corresponding to the first calibration resistor, and the measured resistance value corresponding to the second calibration resistor. This process includes: When the resistance value of the conductivity cell is less than or equal to the measured resistance value corresponding to the first calibration resistor, determine the first difference between the resistance calibration coefficient corresponding to the second calibration resistor and the resistance calibration coefficient corresponding to the first calibration resistor. Determine the second difference between the conductivity cell resistance value and the measured resistance value corresponding to the first calibration resistor, and the third difference between the measured resistance value corresponding to the second calibration resistor and the measured resistance value corresponding to the first calibration resistor; Determine the ratio of the difference between the second difference and the third difference to the second product of the first difference, and obtain the target calibration coefficient based on the sum of the second product and the resistance calibration coefficient corresponding to the first calibration resistor; The calibration resistance value of the conductivity cell is determined by the third product of the target calibration coefficient and the conductivity cell resistance value.

9. The calibration method according to claim 3, characterized in that: The determination of the conductivity calibration coefficient based on the measured conductivity value and the reference conductivity value of the reference solution includes: The conductivity calibration coefficient is determined based on the ratio of the reference conductivity value of the reference solution to the measured conductivity value.

10. A readable storage medium storing a program that, when executed, implements the method as described in any one of claims 3-9.

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