CN110554797B - Sensing method and sensing module of touch control identification device - Google Patents

Abstract

The invention discloses a sensing method of a touch recognition device, comprising: selecting a first sensing electrode as reverse measurement; driving more than one driving electrode, and measuring the first sensing electrode to obtain a first quantity Then measure other sensing electrodes other than the first sensing electrode to obtain other point measurement values; compare the variation value of each point measurement value on the same driving electrode with the first measurement value; check the variation Whether the value is higher or lower than the threshold value; if yes, then judge that the sensing electrode on the point measurement value is abnormal; and, when at least one variation value is higher or lower than the threshold value, stop the touch measurement . The present invention intersperses a judgment program periodically or in real time in the general period wave difference comparison operation of the sensing method, to judge whether there is foreign matter on the touch recognition device when the touch signal is read, and to eliminate the noise signal, To improve the overall sensing accuracy.

Description

Sensing method and sensing module of touch recognition device

【Technical field】

The present invention relates to a sensing method of a touch recognition device and a sensing module thereof, in particular to a sensing method and a sensing module thereof for judging whether there is foreign matter on a touch recognition device when a touch signal is read. To improve the overall sensing accuracy.

【Background technique】

Touch panel or touch screen is one of the main modern human-machine interfaces. As a position recognition device, it can skillfully combine input and display interfaces, so it has the advantages of saving device space and humanized operation, and has been widely used at present. On various consumer or industrial electronic products. For example: personal digital assistant (personal digital assistant, PDA), palm-sized PC (palm-sized PC), tablet computer (tablet computer), mobile phone (mobile phone), information appliance (Information Appliance), sales teller machine (Point-Of-Sale) , POS) and other devices.

The existing capacitive touch panel includes a data processing module, a driving electrode and a sensing electrode, etc., wherein the driving electrode and the sensing electrode are electrically connected to the data processing module through respective interfaces. The driving electrode is composed of a plurality of driving electrode strips parallel to each other, and the sensing electrode is composed of a plurality of parallel sensing electrode strips, wherein each driving electrode strip and each sensing electrode strip are arranged perpendicular to each other to form a plurality of intersections . When the driving electrode is driven by the driving voltage, an electric field is formed between the driving electrode and the sensing electrode, so that the sensing electrode generates an induced charge and has an alternating capacitance, and a plurality of driving electrode strips and a plurality of sensing electrode strips form a plurality of electric fields, so It can be simulated that each intersection has an interaction capacitance, and a plurality of intersections forms an array of interaction capacitance. In a steady-state environment, the interactive capacitance array has a stable capacitance (hereinafter referred to as the base capacitance), so that the sensing electrode generates an induced voltage (the induced voltage at this time is called the base voltage), and the data processing module reads it through its interface. inductive voltage. When a finger or other conductive substance approaches the intersection, it will change the electric field there, causing the induced voltage to change. After the changed induced voltage is transmitted to the data processing module, it is converted into a digital signal by an analog-to-digital converter, and then the algorithm is used to identify whether it is a touch signal, to determine whether to perform the calculation of the touch position, and then process it to form a signal to the host. Output touch information input data. Wherein, the host end is a device controlled by at least one central processing unit (CPU), such as a computer, a PDA, and the like.

Since the electric field formed between the driving electrode and the sensing electrode is easily disturbed by external electromagnetic waves, etc., it is impossible to accurately measure the change of the amount of charge transferred by capacitive charging caused by conductive substances such as fingers. Therefore, in the prior art, there is a method of subtracting the noise by signal subtraction, which repeats a measurement cycle to obtain more than two different sensing voltage signals and then subtracts them. The differential method (deferential) is used to process two or more different sensing voltage signals to obtain a touch signal that eliminates common mode noise. Although the background noise can be eliminated by using the general differential method, it requires two pairs of sensing signals to calculate the differential value, which may cause a decrease in accuracy or resolution due to foreign objects touching during the measurement process.

【Content of invention】

In order to overcome the above-mentioned shortcomings of the prior art, the present invention provides the following various embodiments to solve the above-mentioned problems.

Embodiments of the present invention provide a sensing method of a touch recognition device and a sensing module thereof, which can judge a touch by periodically or real-time interspersedly executing a judging program in the general periodic wave difference comparison operation of the sensing method. Whether there is foreign matter on the touch recognition device when the signal is read, and the sensing method and sensing module for eliminating noise signals, so as to improve the overall sensing accuracy.

In order to achieve one or part or all of the above objectives or other objectives, an embodiment of the present invention provides a sensing method for a touch recognition device, wherein the touch recognition device includes a plurality of sensing electrodes and a plurality of driving electrodes, wherein A plurality of sensing electrodes intersect with a plurality of driving electrodes to have a plurality of nodes, and the sensing method includes the following steps: selecting a first sensing electrode among the plurality of sensing electrodes, and setting the first sensing electrode as an opposite Vector measurement, wherein the first sensing electrode intersects with a plurality of driving electrodes to have a plurality of first nodes; driving one or more driving electrodes, and measuring the first sensing electrodes to obtain the one or more first nodes A first measurement value, and then measure other sensing electrodes other than the first sensing electrode to obtain a plurality of point measurement values of a plurality of nodes; compare each point measurement value on the same driving electrode with the first measurement value respectively A variation value of a measurement value; check whether the variation value is higher or lower than a threshold limit value; if the variation value is higher or lower than the threshold limit value, it is determined that the sensing electrode on which the measurement value is located is abnormal; And, stop a touch measurement when at least one variation value is higher or lower than a threshold value.

In one embodiment, if the number of sensing electrodes determined to be abnormal is at least two, then the touch measurement is stopped.

In one embodiment, if the variation value is not higher than or lower than the threshold value, or the number of abnormal sensing electrodes is less than two, the touch measurement is performed.

In one embodiment, the step of obtaining the first measurement value and the plurality of point measurement values further includes: driving one or a part of the plurality of driving electrodes; measuring the first sensing electrode to obtain one or The first measurement value of more than one first node, and then simultaneously or sequentially measure other sensing electrodes other than the first sensing electrode to obtain one or a part of the plurality of point measurement values; stop driving ; driving another or the remaining part of the plurality of driving electrodes; measuring the first sensing electrode to obtain a first measurement value of one or more first nodes, and then simultaneously or sequentially measuring the first sensing electrodes other sensing electrodes to obtain the other or the rest of the plurality of point measurement values; and repeat the above-mentioned driving action to obtain all the plurality of point measurement values and the plurality of first measurement values.

In one embodiment, the step of obtaining the first measurement value and the plurality of point measurement values further includes: simultaneously driving all of the plurality of driving electrodes; and measuring the first sensing electrodes to obtain all the first nodes The first measurement value of the first sensing electrode is measured, and the other sensing electrodes other than the first sensing electrode are measured at the same time, so as to obtain all the plurality of point measurement values.

In one embodiment, it further includes: selecting another one of the plurality of sensing electrodes as the first sensing electrode, so as to set the first sensing electrode as reverse measurement.

In one embodiment, the step of setting the first sensing electrode as reverse measurement includes electrically connecting the first sensing electrode to a reverse measurement circuit, or a processing unit will perform the measurement cycle through The signal received by the first sensing electrode is reversely processed. The touch measurement further includes: electrically connecting the rest of the plurality of sensing electrodes to a positive vector measurement circuit, and performing touch measurement to obtain a touch signal. The steps of touch measurement include: the reverse measurement circuit sequentially measures with the forward measurement circuit to obtain a reverse signal and a forward signal synchronously; and, receiving the reverse signal through an analog-to-digital conversion circuit signal and forward signal to convert a touch signal, wherein the phase signals of the forward signal and the reverse signal are 180 degrees offset.

In one embodiment, if the variation value is higher than the threshold, it is determined that a pointing object touches the first sensing electrode.

In one embodiment, if the variation value is lower than the threshold value, it is determined that a non-pointing object touches the first sensing electrode.

In order to achieve one or part or all of the above objectives or other objectives, an embodiment of the present invention provides a sensing module of a touch recognition device, including: a plurality of sensing electrodes, including a first reverse measurement a sensing electrode; a plurality of driving electrodes intersecting with the plurality of sensing electrodes to have a plurality of nodes and intersecting with the first sensing electrode to have a plurality of first nodes; and a processing unit electrically connected to the plurality of driving electrodes and a plurality of sensing electrodes, used to drive one or more driving electrodes, measure the first sensing electrodes to obtain a first measurement value of one or more first nodes, and then measure other than the first sensing electrodes other sensing electrodes to obtain a plurality of point measurement values of a plurality of nodes; wherein the processing unit compares each point measurement value on the same drive electrode with a variation value of each first measurement value; the processing unit Checking whether the variation value is higher than or lower than a threshold limit value; if the variation value is higher than or lower than the threshold limit value, the processing unit judges that the sensing electrode on the measured value of the point is abnormal; and when at least one variation value is higher than or lower than the threshold value, the processing unit stops a touch measurement. Wherein, if the variation value is not higher than or lower than the threshold value, or the number of abnormal sensing electrodes is less than two, the processing unit performs touch measurement.

【Description of drawings】

FIG. 1 is a schematic diagram of a sensing module applied to a touch recognition device in a first embodiment of the present invention.

FIG. 2 is a flow chart of a sensing method applied to a touch recognition device in an embodiment of the present invention.

FIG. 3 is a schematic diagram of a sensing module applied to a touch recognition device in the first embodiment of the present invention.

FIG. 4 is a schematic diagram of a sensing module applied to a touch recognition device in a second embodiment of the present invention.

Explanation of reference numbers

100, 200 sensing module

110, 210 processing unit

120(D1-D7), 220(225A-225D) drive electrodes

130(S1-S4), 230(S1-S7) sensing electrodes

【Detailed ways】

Those of ordinary skill in the art can understand that the execution order of the various steps included in the method provided by the embodiment of the present invention does not necessarily follow the order shown in the embodiment, unless there is a specifically stated dependency between the various steps, otherwise the The invention does not limit the execution order of the various steps. Besides, other steps may be inserted between each step without affecting the spirit provided by the present invention. Implementation examples derived in this way also fall within the scope of the present invention.

Please refer to FIG. 1 , which is a sensing module 100 of a touch recognition device in a first embodiment of the present invention. A sensing module 100 of a touch recognition device includes a processing unit 110 , a plurality of driving electrodes 120 and a plurality of sensing electrodes 130 . In this embodiment, the driving electrodes 120 include at least seven driving electrodes D1-D7, and the sensing electrodes 130 include at least four sensing electrodes S1-S4. The plurality of driving electrodes 120 intersect with the plurality of sensing electrodes 130 to have a plurality of nodes D1S1 , D1S2 , D1S3 , D1S4 , D2S1 , D2S2 . . . and so on. The processing unit 110 is electrically connected to the sensing electrode 130 and the driving electrode 120 for driving the driving electrode 120 and sensing the capacitance change on the sensing electrode 130 to obtain a plurality of point measurement values of a plurality of nodes.

The above-mentioned sensing module 100 is used to implement a sensing method of a touch recognition device in the following embodiments of the present invention.

Please refer to FIG. 2 , which is a schematic flowchart of a sensing method of a touch recognition device in an embodiment of the present invention, and is illustrated in conjunction with FIGS. 3 and 4 . The sensing method of the embodiment of the present invention includes the following steps S100-S700 to execute the determination procedure and cooperate with the touch measurement.

Step S100: Select a first sensing electrode among the plurality of sensing electrodes S1-S4. In this embodiment, the sensing electrode S1 is preselected as the first sensing electrode, and the sensing electrode S1 is set to be used for reverse measurement. The first sensing electrode S1 intersects with the plurality of driving electrodes D1-D7 to have a plurality of first nodes D1S1, D2S1, D3S1, . . . and so on. The step of setting the sensing electrode S1 as the reverse measurement includes electrically connecting the sensing electrode S1 to a reverse measurement circuit, so that the processing unit 110 can use the first sensing The signal received by the electrode S1 is reversely processed, for example, multiplied by a negative sign, so as to save calculation time.

Step S200: Drive one or more driving electrodes, measure the first sensing electrode to obtain the measurement value of one or more first nodes, and then measure other sensing electrodes other than the first sensing electrode to obtain Multiple point measurements for other multiple nodes. In this embodiment, the point measurement values of the plurality of nodes or the first node measurement value are variation values generated by periodic wave driving.

In one embodiment, the step of obtaining the first measurement value and the plurality of point measurement values further includes: driving one or a part of the driving electrodes; measuring the first sensing electrodes to obtain one or more The first measurement value of the first node, and then simultaneously or sequentially measure other sensing electrodes other than the first sensing electrode, so as to obtain one or a part of the plurality of point measurement values; stop driving; drive The other or the remaining part of the plurality of drive electrodes; measure the first sensing electrode to obtain the first measurement value of one or more first nodes, and then simultaneously or sequentially measure the first sensing electrode other than the first sensing electrode other sensing electrodes to obtain another or the rest of the plurality of point measurement values; and repeat the above driving action to obtain all point measurement values and the first measurement value.

In the first embodiment, as shown in FIG. 3 , the driving electrode D1 is driven first, and point measurement values of different nodes D1S1, D1S2, D1S3, and D1S4 are sequentially obtained, including a first measurement value of the first node D1S1. . Next, drive the driving electrode D2 sequentially in the direction of the arrow to obtain point measurement values of different nodes D2S1 , D2S2 , D2S3 , and D2S4 , including the first measurement value of the first node D2S1 . Then, drive the driving electrodes D3 and D4 sequentially to obtain point measurement values of all the nodes D3S1 , D3S2 , D3S3 , D3S4 , D4S1 , D4S2 , D4S3 , and D4S4 .

FIG. 4 is a sensing module 200 of a touch recognition device in the second embodiment of the present invention. The sensing module 200 includes a processing unit 210 , a plurality of driving electrodes 220 and a plurality of sensing electrodes 230 . The processing unit 210 is electrically connected to the sensing electrode 230 and the driving electrode 220 . In this embodiment, the driving electrodes 220 are divided into four parts, namely the first part of driving electrodes 225A-225D, and the sensing electrodes 230 include at least seven sensing electrodes S1-S7. The plurality of driving electrodes 220 intersect with the plurality of sensing electrodes 230 to have a plurality of nodes, and the sensing electrode S1 is still selected as the first sensing electrode. In the second embodiment, the first part of the driving electrodes 225A is driven first, and point measurement values of different nodes 225AS1 , 225AS2 , 225AS3 . . . are sequentially obtained, including a first measurement value of the first node D1S1 . Next, drive the second part of the driving electrodes 225B sequentially in the direction of the arrow, and then drive the third part of the driving electrodes 225C and the fourth part of the driving electrodes 225D, so as to obtain point measurement values of all nodes.

In the above-mentioned embodiment of this step S200, the present invention is not limited to obtaining all point measurement values and the first measurement value in this step, one or a part of the driving electrodes may be driven first, and then After obtaining the first measurement value of the first sensing electrode and the point measurement values of a plurality of nodes of one or a part of the sensing electrode, the next step S300-S400 can be continued, and then return to step S200 to All point measurements and the first measurement are obtained.

In one embodiment, referring to FIG. 3 again, the driving electrode D1 is driven for the first time, and point measurement values of different nodes D1S1, D1S2, D1S3, and D1S4 are sequentially obtained, including a first quantity of the first node D1S1. measured value. Next, following the direction of the large black arrow, the driving electrode D4 is directly skipped for the second time to obtain point measurement values of different nodes D4S1, D4S2, D4S3, and D4S4, including the first measurement value of the first node D4S1. Then, continue to skip and drive other driving electrodes. Wherein, the second driving can directly skip the driving electrode D4, that is, the distance from the driving electrode D1 of the first driving is separated by 3 driving electrodes; 4-5 driving electrodes D5 or D6 are provided to speed up the response time of the sensing method.

In another embodiment, the step of obtaining the first measurement value and the plurality of point measurement values further includes: simultaneously driving all of the plurality of driving electrodes; and measuring the first sensing electrodes to obtain all first The first measurement value of the node, and then measure other sensing electrodes other than the first sensing electrode at the same time, so as to obtain all the plurality of point measurement values.

Step S300: Compare the measured value of each point on the same driving electrode with a variation value of the first measured value. In the first embodiment shown in FIG. 2 , in step S200, after driving the driving electrode D1, the variation values between the first measured value of the first node D1S1 and other nodes D1S2, D1S3, and D1S4 are sequentially obtained, Then proceed to step S400; or after driving the driving electrode D2 again, sequentially obtain the variation values between the first measured value of the first node D2S1 and other nodes D2S2, D2S3, and D2S4, and then proceed to step S400.

Step S400: Check whether the variation value obtained in step S300 is higher or lower than a threshold set by the sensing module. The measured values sensed by the above-mentioned sensing electrodes are variations generated by the periodic wave driving, and the differences between the two are compared by steps S300-S400. When a non-pointing object such as a finger or a stylus touches the sensing module, if the sensing module wants to determine whether there is another foreign object touching it, the periodic wave drive variation attenuation comparison is performed, because the sensing measurement value will be touched Non-pointing objects such as bumps or other foreign objects (such as water stains) cause attenuation, so the above steps are for observing and judging whether the attenuation is caused by non-pointing objects. If the variation value is higher than the threshold value, it is determined that there is a pointing object touching the first sensing electrode. If the variation value is lower than the threshold value, it is determined that a non-pointing object touches the first sensing electrode.

Step S500: If the variation value is higher or lower than the threshold value, it is determined that the sensing electrode where the measurement value of this point is located is abnormal. As shown in FIG. 3 , since the variation values between the nodes D1S2 and D4S3 and the first nodes D1S1 and D4S1 are higher or lower than the threshold value, it is determined that the sensing electrodes S2 and S3 are both abnormal. As shown in FIG. 4 , since the variation values between the node regions 225AS2 and 225CS4 and the first nodes 225AS1 and 225CS1 are higher or lower than the threshold, it is determined that the sensing electrodes S2 and S4 are both abnormal.

Step S600 : continue with step S500 , and stop a touch measurement when at least one variation value is higher or lower than a threshold value. In a preferred embodiment, if the number of sensing electrodes judged to be abnormal is at least two, then the touch measurement is stopped.

When it is judged that the first sensing electrode is touched by a finger or there is a foreign object on it, the previously obtained node measurement value signal is used to cover the old reading point measurement value with the newly read point measurement value; Alternatively, old point measurement values can be directly discarded and not used.

Step S700 : continue with step S600 , select another one of the plurality of sensing electrodes as the first sensing electrode and set it as reverse measurement. The above steps S100-S600 are repeated to re-execute the judging procedure.

The judging procedure of the above-mentioned sensing method may adopt periodic detection or real-time detection. If periodic detection is used, after performing several touch measurements, execute this judgment procedure once to scan the entire panel to confirm whether the sensing electrode selected as the reverse measurement is appropriate; if real-time detection is used, Then the judgment is made after comparing the variation and attenuation of each periodic wave under the touch measurement. Every time the node signal is obtained for periodic wave variation and attenuation comparison, the variation value is first judged according to the conditions set by the touch system whether the first sensing electrode, which is the reverse measurement, has been touched, and then other signal processing or judgment is performed, such as report.

Step S510 : continue with step S400 , if the variation value is not higher than or lower than the threshold value, or if the number of abnormal sensing electrodes is less than two, perform touch measurement. In this embodiment, in addition to electrically connecting the sensing electrode S1 to a reverse measurement circuit, the touch measurement further includes: electrically connecting the rest of the plurality of sensing electrodes to a forward measurement circuit, and A touch signal is obtained by performing touch measurement. The steps of performing touch measurement include: the reverse measurement circuit sequentially performs measurement with the forward measurement circuit to obtain a reverse signal and a forward signal synchronously; and, receiving the reverse signal through an analog-to-digital conversion circuit signal and forward signal to convert a touch signal, wherein the phase signals of the forward signal and the reverse signal are 180 degrees offset.

Embodiments of the present invention provide a sensing method of a touch recognition device and a sensing module thereof, which can judge a touch by periodically or real-time interspersedly executing a judging program in the periodic wave variation attenuation comparison operation of the sensing method. A sensing method and a sensing module thereof for whether there is foreign matter on the touch recognition device during signal reading are used to improve the overall sensing accuracy.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the scope of the present invention; any equivalent changes or modifications that do not deviate from the disclosed spirit of the invention are understood to be included in the following claims within a limited range.

Claims (13)

1. A sensing method of a touch recognition device, wherein the touch recognition device includes a plurality of sensing electrodes and a plurality of driving electrodes, the plurality of sensing electrodes and the plurality of driving electrodes intersect and have a plurality of nodes, the sensing method comprising the steps of:

selecting a first sensing electrode of the plurality of sensing electrodes, and setting the first sensing electrode to be reversely measured, wherein the first sensing electrode intersects with the plurality of driving electrodes to have a plurality of first nodes;

driving one or more driving electrodes, measuring the first sensing electrode to obtain a first measurement value of one or more first nodes, and measuring the sensing electrodes except the first sensing electrode to obtain a plurality of point measurement values of the plurality of nodes;

comparing a variation value between each point measurement value and the first measurement value on the same driving electrode;

checking whether the variance is above or below a threshold value;

if the variation value is higher than or lower than the threshold value, judging that the sensing electrode on the point measurement value is abnormal; the method comprises the steps of,

and stopping touch measurement when at least one variation value is higher or lower than the threshold value.

2. The method of claim 1, wherein the touch measurement is stopped when the number of the sensing electrodes is at least two.

3. The method of claim 1, wherein the touch measurement is performed if the variance is not higher than or lower than the threshold value or the number of anomalies in the sensing electrode is less than two.

4. The method of claim 1, wherein the step of obtaining the first measurement value and the plurality of point measurements further comprises:

driving one or a portion of the plurality of drive electrodes;

measuring the first sensing electrode to obtain the first measurement value of one or more first nodes, and simultaneously or sequentially measuring the sensing electrodes except the first sensing electrode to obtain one or a part of the plurality of point measurement values;

stopping driving;

driving another or the remaining portion of the plurality of driving electrodes;

measuring the first sensing electrode to obtain the first measurement value of one or more first nodes, and simultaneously or sequentially measuring the other sensing electrodes except the first sensing electrode to obtain another one or the rest of the plurality of point measurement values; the method comprises the steps of,

repeating the driving operation to obtain all the plurality of point measurement values and the plurality of first measurement values.

5. The method of claim 1, wherein the step of obtaining the first measurement value and the plurality of point measurements further comprises:

simultaneously driving all of the plurality of driving electrodes;

measuring the first sensing electrode to obtain the first measurement value of all the first nodes; the method comprises the steps of,

simultaneously measuring the sensing electrodes except the first sensing electrode to obtain all the plurality of point measurement values.

6. The method of claim 1, further comprising selecting another one of the plurality of sense electrodes as the first sense electrode to set the first sense electrode to a reverse measurement.

7. The method of claim 1, wherein the step of providing the first sensing electrode as a reverse measurement comprises electrically connecting the first sensing electrode to a reverse measurement circuit or a processing unit reversing the signal received via the first sensing electrode during the measurement cycle.

8. The method of claim 7, further comprising electrically connecting the remaining ones of the plurality of sensing electrodes to a forward measuring circuit and performing the touch measurement to obtain a touch signal.

9. The method for sensing according to claim 8, wherein the step of touch measurement comprises:

the reverse measurement circuit sequentially measures with the forward measurement circuit to synchronously obtain a reverse signal and a forward signal respectively; the method comprises the steps of,

the reverse signal and the forward signal are received by an analog-digital conversion circuit to obtain a touch signal, wherein the phase signals of the forward signal and the reverse signal are 180-degree offset.

10. The method of claim 1, wherein if the variance is higher than the threshold value, determining that a pointing object touches the first sensing electrode.

11. The method of claim 1, wherein if the variance is less than the threshold value, determining that a non-pointing object touches the first sensing electrode.

12. A sensing module of a touch recognition device, comprising:

a plurality of sensing electrodes including a first sensing electrode configured for reverse measurement;

a plurality of driving electrodes intersecting the plurality of sensing electrodes to have a plurality of nodes, intersecting the first sensing electrodes to have a plurality of first nodes; the method comprises the steps of,

the processing unit is electrically connected with the plurality of driving electrodes and the plurality of sensing electrodes and is used for driving one or more driving electrodes, measuring the first sensing electrode to obtain a first measurement value of one or more first nodes, and measuring the sensing electrodes except the first sensing electrode to obtain a plurality of point measurement values of the plurality of nodes;

the method is characterized in that: the processing unit compares each point measurement value on the same driving electrode with a variation value of each first measurement value; the processing unit checks whether the variance is above or below a threshold value; if the variation value is higher than or lower than the threshold value, the processing unit judges that the sensing electrode on the point measurement value is abnormal; and stopping a touch measurement by the processing unit when at least one of the variants is higher or lower than the threshold value.

13. The sensing module of claim 12, wherein the processing unit performs the touch measurement if the variance is not higher than or lower than the threshold value or if the number of abnormal sensing electrodes is less than two.

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