A multi-step measurement method and test circuit for a resistive sensor array

Abstract

The application discloses a kind of multi-step measurement method and test circuit of resistive sensor array, and the application is aimed at M×N two-dimensional resistive sensor array of common row line and column line;The test circuit includes: 1 inverting operational amplifier, 1 voltage follower, several row multiplexers, several column multiplexers.Resistive sensor array row line and column line can be accessed the output end of voltage follower by multiplexer, and the inverting input end of voltage follower can also be accessed the row line and column line of resistive sensor array by multiplexer.At the same time, resistive sensor array row line and column line can also be accessed the inverting input end of inverting operational amplifier by multiplexer, and the noninverting input end of inverting operational amplifier is grounded.Compared with prior art, the application can accurately measure the resistance value of any to-be-measured resistor in the array, and effectively eliminates the interference of crosstalk and switch-on resistance, while having strong anti-interference performance and simple structure.

Description

Technical Field

[0001] This invention belongs to the field of sensor technology, specifically relating to a multi-step measurement method and test circuit for a resistive sensor array. Background Technology

[0002] An array-type sensing device is a sensing device formed by combining multiple sensing elements with the same performance in a two-dimensional array. Through a specific reading method, it can detect changes in the parameters of the sensing elements in the array to generate corresponding shapes and features. These shapes and features are widely used in infrared imaging simulation, force and tactile sensing, and temperature and tactile sensing.

[0003] Taking handwriting trajectory tracking and recognition technology as an example, two-dimensional impedance sensor arrays play a crucial role. Handwriting trajectory tracking and recognition technology aims to improve the accuracy and efficiency of handwriting recognition by studying the acquisition, processing, and recognition algorithms of handwriting trajectory data. This technology can be used in education for handwritten answer sheet recognition and in finance for handwritten signature authentication. However, traditional static image-based recognition methods have limited accuracy and robustness when processing complex dynamic handwriting trajectories. Two-dimensional sensor arrays can detect subtle changes in handwriting strokes with high resolution and precision, acquiring rich handwriting trajectory information, meeting the data acquisition accuracy and density requirements of handwriting trajectory tracking and recognition technology, and providing more accurate data support for subsequent recognition algorithms combined with machine learning.

[0004] Improving the accuracy and density of resistive sensor arrays typically requires increasing the number of sensors in the array. However, as the array size increases, the complexity of information acquisition and signal processing increases significantly. Taking an M×N resistive sensor array as an example, to access all sensors individually, with each sensor having two ports, a total of 2×M×N connection lines are needed. This connection method has many drawbacks: complex wiring, difficult to manage; complex and chaotic current paths, making it difficult to obtain accurate measurements. This not only limits the practical application of large-scale arrays but also increases the complexity and cost of system design. To address this problem, current research has developed a two-dimensional resistive sensor array structure with shared row and column lines. This array contains two sets of orthogonal lines, serving as shared row and column lines respectively, and an array of physical quantity-sensitive resistors (i.e., resistive sensors) distributed in an M×N two-dimensional structure. One end of each physical quantity-sensitive resistor in the array is connected to the corresponding row line, and the other end is connected to the corresponding column line. Each resistor has a unique row and column line combination, where the resistor in the x-th row and y-th column is... In this configuration, M represents the number of rows and N represents the number of columns. With this structure, for an M×N two-dimensional array, only M+N connections are needed to ensure that any specific resistive element can be accessed by controlling the appropriate combination of row and column lines, significantly reducing the number of connections required.

[0005] Impedance sensor arrays sharing row and column lines typically rely on multiplexers to sequentially access different sensor units. The on-resistance of the multiplexer channels significantly impacts measurement accuracy. For impedance sensor array measurements, the presence of on-resistance results in a suboptimal connection between the test circuit and the sensor array. Specifically, the multiplexer on-resistance introduces additional voltage errors between the test circuit's drive terminals and the row and column lines of the sensor array module, and also generates voltage errors between the row and column lines and the inverting input of the inverting operational amplifier. These voltage errors disrupt the ideal feedback conditions of the test circuit, leading to deviations in the measured resistance values. Furthermore, parasitic parameters inevitably influence actual measurement circuits. These include parasitic coupling capacitances such as the coupling capacitance between multiplexer channels, distributed capacitance between array row and column lines, coupling capacitance between adjacent PCB traces, and conductor-to-ground capacitance; and additional parasitic resistances such as conductor resistance, connector and solder joint contact resistance, PCB surface leakage resistance, and leakage path resistance caused by factors such as device leakage current. These non-ideal factors all negatively impact measurement accuracy. Especially under dynamic measurement conditions, parasitic coupling capacitance, due to its energy storage and coupling functions, introduces additional current during signal changes or channel switching. This alters the voltage build-up process at the measurement node and the branch current distribution, leading to output response lag, amplitude deviation, and increased crosstalk between channels. Simultaneously, the parallel connection between sensor array units can cause current shunting or superposition of currents in the output branches of the measured unit, also introducing crosstalk and causing deviations in resistance measurement results.

[0006] Therefore, how to effectively eliminate or compensate for the on-resistance of multiplexer closure, crosstalk caused by the superposition of different branches on the output branch, and the influence of other environmental factors such as changes in non-measured resistors (as mentioned above, the handwriting tablet will affect non-measured resistors when the hand is near) or parasitic parameters on measurement accuracy has become an important research topic for improving the measurement accuracy and reliability of impedance sensor arrays. Summary of the Invention

[0007] To address the aforementioned issues, this invention discloses a high-precision multi-step measurement circuit and its measurement method, which can effectively eliminate the conduction resistance of switch closure and has strong shielding performance against interference introduced by changes in non-target objects, thus meeting the high-precision measurement and spatial resolution requirements of the aforementioned fields.

[0008] To achieve the above objectives, the technical solution of the present invention is as follows:

[0009] The test object of this invention is an M×N two-dimensional resistive sensor array employing a shared row and column line structure. The measurement circuit of the array specifically includes: one inverting operational amplifier, one voltage follower, several row multiplexers, and several column multiplexers.

[0010] The non-inverting input of the inverting operational amplifier is grounded, which is at zero potential. A resistor connects the inverting input to the output. The inverting operational amplifier achieves inverting amplification through connection. Due to its virtual short characteristic, the inverting input of the inverting operational amplifier is also at zero potential. By closing and opening the row and column multiplexers, the inverting input of the inverting operational amplifier can be selected to be connected or disconnected from any row and column line of the array.

[0011] A fixed potential is connected to the non-inverting input of the voltage follower. Through row and column multiplexers, the inverting input and output of the voltage follower can be selected to be turned on or off with any row and column of the array.

[0012] The testing method of this invention is as follows:

[0013] Scan all array resistors one by one, with the resistors to be measured ranging from hundreds of ohms to thousands of ohms. Select one resistor to be measured. Its conductivity is The measurement is performed to determine the row and column lines in which it is located. The measurement process includes multiple steps, and the conductivity values ​​obtained in each step are as follows: , , Meanwhile, since a small-resistance multiplexer of the same model is selected, the on-resistance value when the multiplexer is closed is assumed to be... The same, its corresponding conductivity value is :

[0014] Step one: Using a multiplexer, all column lines and all row lines other than those containing the currently measured resistor are connected to the inverting input of the inverting operational amplifier. The row line containing the currently measured resistor is simultaneously connected to both the output and inverting input of the voltage follower. Therefore, under the action of the voltage follower, the potential of the row line containing the currently measured resistor... Under the action of the inverting operational amplifier, the potential of all column lines and all row lines other than the one currently being measured is zero. (At zero potential). The voltage at the output of the inverting operational amplifier is Then the current at the inverting input of the inverting operational amplifier is Therefore, we can obtain the first formula for calculating conductivity:

[0015] (1);

[0016] in, The current conductance of the resistor being measured is... The array resistors that are in the same row as the resistor being measured ( , does not include The total conductance of all resistors in the branches containing adjacent array resistors in each row is connected in parallel with the resistor being measured. The array resistors that are in the same column as the resistor being measured ( , does not include The conductance of all resistors in the branches containing adjacent array resistors is connected in series with the resistor being measured. This is the conductance of the on-resistance of the switch connected to the inverting input of the inverting operational amplifier, where the current measured resistor column line is connected.

[0017] Step two: Connect the column line containing the resistor being measured to both the output and inverting input of the voltage follower. Connect all other row lines and all column lines not containing the resistor being measured to the inverting input of the inverting operational amplifier. Therefore, under the action of the voltage follower, the potential of the column line containing the resistor being measured is... Under the action of the inverting operational amplifier, the potential of all row lines and all column lines other than those containing the resistor being measured is zero. Similarly to the first step, the second conductance calculation formula can be obtained:

[0018] (2);

[0019] in, The current is still the conductance of the resistor being measured. and The definition is the same as above, at this time Connected in parallel with the resistance being measured. Connected in series with the resistance being measured. This is the conductance of the on-resistance of the switch connected to the inverting input of the inverting operational amplifier along the row line of the resistor being measured; here, it is assumed that the on-resistance of the row and column switches is the same.

[0020] Step 3: Connect the row and column lines containing the resistor being measured to the output and inverting input of the voltage follower simultaneously. Connect all other row and column lines not containing the resistor being measured to the inverting input of the inverting operational amplifier. Therefore, under the action of the voltage follower, the potential of the column and row lines containing the resistor being measured is... Under the action of the inverting operational amplifier, the potential of all row and column lines not containing the currently measured resistor is zero. Similar to the previous two steps, the final conductance calculation formula can be obtained:

[0021] (3);

[0022] Combining the three formulas above, we can derive:

[0023] (4);

[0024] Among them, due to and Much larger ,but as well as All are much smaller than ,but and The impact is negligible, and therefore we can deduce that:

[0025] (5);

[0026] in, The resistance being measured is currently... for The on-resistance when the switch connecting the row and column lines to the inverting input of the inverting operational amplifier is closed.

[0027] The beneficial effects of this invention are as follows:

[0028] 1. Through a multi-step measurement method, this invention can accurately measure the resistance value of each resistor in the resistive sensor array, while also improving measurement accuracy and greatly enhancing the scalability of the resistive sensor array.

[0029] 2. When environmental interferences such as changes in resistance values ​​of non-current resistors, capacitive crosstalk, current shunting, and power supply fluctuations occur during the measurement of the current resistor being measured, this invention can focus the measurement results on the current resistor being measured and eliminate changes in resistance values ​​of non-current resistors and other interferences through calculation, thereby achieving high-precision measurement.

[0030] 3. This invention addresses the detection needs of resistive sensor arrays, featuring a simple circuit structure and easy wiring. Combined with a voltage follower, it effectively eliminates the on-resistance of multiplexers. Furthermore, this invention maintains consistency in device configuration and exhibits symmetry in circuit structure and detection method. This not only enhances the stability of measurement results but also mitigates the adverse effects of non-ideal factors such as parasitic coupling capacitance, parasitic resistance, current shunting, and crosstalk on measurement accuracy, achieving high-precision and reliable detection under dynamic measurement conditions.

[0031] 4. Due to the isolation effect of the voltage follower, the present invention can use a low-cost multiplexer, reducing the cost of the test circuit. Attached Figure Description

[0032] Figure 1 This is a diagram of the classic M×N two-dimensional resistive sensor array structure used in this invention;

[0033] Figure 2 This is a schematic diagram illustrating the specific implementation of the first step of the test circuit of the present invention (for measurement). (For example);

[0034] Figure 3 This is a schematic diagram of the first step of the test circuit of the present invention (for measurement). (For example);

[0035] Figure 4 This is a schematic diagram illustrating the specific implementation of the second step of the test circuit of the present invention (for measurement). (For example);

[0036] Figure 5 This is a schematic diagram of the second step of the test circuit of the present invention (for measurement). (For example);

[0037] Figure 6 This is a schematic diagram illustrating the specific implementation of the third step of the test circuit of the present invention (for measurement). (For example);

[0038] Figure 7 This is the schematic diagram of the third step of the test circuit of the present invention (for measurement). (For example);

[0039] Figure 8 A simplified comparison diagram of the equivalent principle of the three steps of the test circuit of this invention (for measurement). (For example). Detailed Implementation

[0040] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0041] Figure 1 The diagram illustrates a classic M×N two-dimensional resistive sensor array structure with shared rows and columns. As can be seen, only one resistor exists between any row and any column. This means that to measure the corresponding resistance, one must start by examining the row and column containing the resistor. However, direct measurement would require starting from... Figure 2As can be seen from the schematic diagram of the first step, without the zero-potential constraint, the current flowing from the corresponding column will flow through other branches and eventually return to the corresponding column, which is the interference of current crosstalk. In addition, even with the zero-potential constraint, other branches will still shun the total current, causing measurement errors. The test circuit also contains multiple switches, which in practice have on-resistance, also contributing to measurement errors. Most existing measurement methods focus on addressing these two major error-causing factors. Consistent with other methods, this invention also addresses these two major factors. It uses the isolation effect of a voltage follower to avoid the influence of the switch's on-resistance on the measurement results, and employs a novel measurement method to solve crosstalk interference. Furthermore, compared to other methods, this invention uses a method of mutual cancellation to eliminate interference. Even if changes occur around or within the non-measured resistor, they will not affect the final measurement result of the measured resistor, thus isolating interference caused by changes in the non-measured resistor and its environment to a certain extent.

[0042] like Figure 2 The wiring method of the sensor array shown in this invention involves connecting single-pole double-throw (SPD-D) and single-pole single-throw (SPS-S) switches at the ports of each row and column line. These switches are used to select whether to connect to the output of a voltage follower or the inverting input of an inverting operational amplifier, and to select whether to connect to the inverting input of the voltage follower. It should be noted that when connecting to the output of the voltage follower, the inverting input must be connected to the corresponding row or column line to achieve the voltage following effect. Thus, each row and column line will only have two connection options: one is to connect to the output and inverting input of the voltage follower, and the other is to connect to the inverting input of the inverting operational amplifier, i.e., zero potential. The inverting input of the voltage follower is disconnected. Next, we will measure the resistance. Let's continue with an example:

[0043] Measuring resistance At that time, proceed with the first step, such as Figure 2 As shown, the corresponding row lines are connected to the output of the voltage follower, and the corresponding column lines are connected to the inverting input of the inverting operational amplifier. Due to the isolation effect of the voltage follower, the switching resistance existing on the row lines is isolated, thus forming... Figure 3 The diagram shown is an equivalent representation of the principle. It represents electric current. and The parallel equivalent resistance of all resistors along the flow path, similarly, It represents electric current. and The parallel equivalent resistance of all resistors along the flow path. From Figure 3 It can be seen that, and Parallel, and and and The parallel equivalent resistances are connected in series. Then, using the definition of Ohm's law and the concept of conductance, we can know that:

[0044] (1);

[0045] To facilitate measurement, an inverting operational amplifier is connected to the output terminal of this invention, which is derived from the calculation formula of the inverting operational amplifier:

[0046] (2);

[0047] in, The current conductance of the resistor being measured is... For current and The conductance of the parallel equivalent resistance of all resistors flowing through the path is connected in parallel with the resistor being measured. For current and The conductance of the parallel equivalent resistance of all resistors in the path is connected in series with the resistor being measured. The conductance is the on-resistance of the switch that connects the current measured resistor column line to the inverting input terminal of the inverting operational amplifier.

[0048] Then proceed to the second step, such as Figure 4 The schematic diagram for the second step shows that the row input is connected to the inverting input of the operational amplifier, and the column input is connected to the output of the voltage follower. Unlike the first step, the on-resistance present on the row lines is now present, while the on-resistance present on the column lines is isolated. and Parallel equivalent resistance and Series, and Then and Following the same logic as the steps, we can obtain the following:

[0049] (3);

[0050] Finally, proceed to the third step, such as... Figure 6 The schematic diagram for the third step shows that the row and column interfaces are connected to the output of the voltage follower. Therefore, the switching resistances existing on both the row and column lines are isolated by the voltage follower. Simultaneously, since the resistance being measured... The voltage at both ends is Therefore, the resistance being measured is No current will flow, so only and By connecting them in parallel, we obtain the calculation formula for the third step:

[0051] (4);

[0052] Using formulas (2) to (4), we obtain the following formulas:

[0053] (5);

[0054] For ease of understanding, Figure 8 A simplified equivalent diagram of the three steps of the multi-step measurement method is shown. Because... and Much larger ,but as well as All are much smaller than ,but and The effect can be ignored, so formula (5) can be simplified to the following calculation formula:

[0055] (6);

[0056] The expression for resistance is as follows:

[0057] (7);

[0058] The left side of formula (7) represents the known values ​​obtained from measurement. The resistance can be obtained from the switch's datasheet, and thus the current resistance being measured can be calculated. The value is:

[0059] (8);

[0060] From the perspective of the calculation method, since the present invention eliminates each other through calculations in different steps, even if resistive or capacitive interference occurs in other parallel branches of the currently measured resistor, such as the handwritten trajectory tracking mentioned in the present invention, even if the impedance of other non-currently measured resistors changes slightly when the hand approaches them, as can be seen from the formula, the non-currently measured resistors and their additional interference will eventually cancel each other out, leaving only the currently measured resistor, and will not affect the result of the currently measured resistor.

[0061] Example verification: For the simplified process in the formula, taking a 4×4 array as an example, assume the resistance in the array (including the resistance currently being measured) The resistance values ​​are all 900 ohms. The resistance is 0.5 ohms, then , Approximately One-third of that, taken as 300 ohms, yields the following calculation result:

[0062] (9);

[0063] (10);

[0064] (11);

[0065] From formulas (9) to (11), it can be seen that in and Much larger Under these conditions, simplification has a negligible impact on the final result.

[0066] In summary, using the test circuit of this invention, any resistor to be tested in the array can be accurately measured, and interference from cross-current and the on-resistance of the switch are eliminated. It also has strong anti-interference performance, simple wiring, and a simple measurement method, making it easy to operate.

[0067] It should be noted that the above content merely illustrates the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. For those skilled in the art, various improvements and modifications can be made without departing from the principle of the present invention, and all such improvements and modifications fall within the scope of protection of the claims of the present invention.

Claims

1. A test circuit for a resistive sensor array, wherein the resistive sensor array is an M×N two-dimensional resistive sensor array sharing row and column lines, characterized in that: The test circuit specifically includes: one inverting operational amplifier, one voltage follower, several row multiplexers, and several column multiplexers; The row and column lines of the resistive sensor array are connected to the output and inverting input of the voltage follower via a multiplexer; The row and column lines of the resistive sensor array are connected to the inverting input of the inverting operational amplifier via a multiplexer, and the non-inverting input of the inverting operational amplifier is grounded. The multiplexer controls whether the row and column lines of the resistive sensor array are connected to the output of the voltage follower or the inverting input of the inverting operational amplifier, and also controls the connection between the row and column lines and the inverting input of the voltage follower.

2. The test circuit as described in claim 1, characterized in that, The non-inverting input terminal of the voltage follower is connected to a fixed potential. The non-inverting input of the inverting operational amplifier is connected to zero potential, and a negative feedback resistor is connected between its output and inverting input. .

3. The test circuit as described in claim 1, characterized in that, The row and column multiplexer includes the common terminal of M+N single-pole double-throw switches and one end of M+N single-pole double-throw switches connected to M row lines and N column lines in a one-to-one correspondence. Each row line and column line is used to disconnect and connect to the inverting input and output terminals of the voltage follower, and can also disconnect and connect to the inverting input terminal of the inverting operational amplifier.

4. The multi-step measurement method for the circuit as described in claim 1, characterized in that, To measure the resistance of any resistive sensor in the resistive sensor array, the multi-step measurement method is as follows: Step 1: For the row and column lines of the resistor under test, connect one end of a row line to the output and inverting input of the voltage follower, and connect all other row and column lines to the inverting input of the inverting operational amplifier; the non-inverting input voltage of the voltage follower is... The output of the inverting operational amplifier is Then we get the following conductivity formula: （1）； in, The current conductance of the resistor being measured is... For current and The conductance of the parallel equivalent resistance of all resistors flowing through the path is connected in parallel with the resistor being measured. For current and The conductance of the parallel equivalent resistance of all resistors in the path is connected in series with the resistor being measured. The conductance is the on-resistance of the switch that connects the current measured resistor column line to the inverting input terminal of the inverting operational amplifier. Step 2: Connect one column line to the output and inverting input of the voltage follower. Connect all other row and column lines to the inverting input of the inverting operational amplifier. The non-inverting input voltage of the voltage follower is... The output of the inverting operational amplifier is Then we get the following conductivity formula: （2）； in, The current conductance of the resistor being measured is... For current and The conductance of the parallel equivalent resistance of all resistors in the path is connected in series with the resistor being measured. For current and The conductance of the parallel equivalent resistance of all resistors flowing through the path is connected in parallel with the resistor being measured. The conductance is the on-resistance of the switch that connects the current measured resistor column line to the inverting input terminal of the inverting operational amplifier. Step 3: Connect both ends of the row and column lines of the resistor under test to the output and inverting input of the voltage follower. Connect all other row and column lines to the inverting input of the inverting operational amplifier. The non-inverting input voltage of the voltage follower is... The output of the inverting operational amplifier is Then we get the following conductivity formula: （3）； By using voltage and current to obtain the conductance at each step, and combining this with the three formulas above, we can derive: （4）； Among them, due to and Much larger ,but as well as All are much smaller than ,but and Neglecting the impact, the final simplified results for both are... Then, the resistance of the resistive sensor under test is calculated using the following formula. : （5）； in, , , These are the conductances measured in the first, second, and third steps, respectively. This is the on-resistance of the multiplexer.

5. A sensing system, comprising a resistive sensor array and corresponding test circuitry, characterized in that, The resistive sensor array is an M×N two-dimensional resistive sensor array with shared row and column lines, and the test circuit is the resistive sensor array test circuit based on the multi-step measurement method as described in claim 4.

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