TW201324290A - Capacitive induction system and device, touch device - Google Patents

Abstract

Disclosed is a capacitive induction device, including: a capacitive sensor which correspondingly produces an induction capacitance that varies along the distance from an object and includes an induction board, and a separator between the induction board and the ground, where the separator and the induction board are electrically connected into a short-circuit; a capacitance readout circuit electrically connecting to the capacitive sensor and alternatively performing charging and discharging to the capacitive sensor, so as to produce an output signal with its frequency following the variation of the induction capacitance.

Description

Capacitive sensing system and device, touch device

The present invention relates to a system and device, and more particularly to a capacitive sensing system and device, and a touch device.

As shown in FIG. 1, a conventional Proximity capacitive sensor 18 is adapted to sense whether an object 20 is in proximity because most of the power lines are absorbed by the ground 16, resulting in the capacitive sensor 18 and the object 20. The induced capacitance between them decreases, and the sensing distance of the capacitive sensor 18 decreases.

As shown in FIG. 2 and FIG. 3, a conventional capacitive sensing device is disclosed in US Pat. No. 5,166,679, which is adapted to sense whether an object 20 (such as a robot) is in proximity, and the capacitive sensing device comprises a capacitive sensor 10, A buffer 11 and a frequency oscillator 12.

The capacitive sensor 10 has a sensing plate 18 and a shielding plate 22 interposed between the sensing plate 18 and the ground 16.

The buffer 11 is electrically connected between the sensing board 18 and the isolation board 22, so that the sensing board 18 and the isolation board 22 reach the same potential, because the equipotential does not have a power line, and the power line to the ground is almost The isolation plate 22 is provided, and the power line of the induction plate 18 is emitted toward the object 20, thereby increasing the inductive capacitance between the sensing plate 18 and the object 20, thereby increasing the sensing distance of the capacitive sensor 10.

The frequency oscillator 12 is electrically connected to the sensing board 18, and generates an oscillating signal whose frequency varies with capacitance according to whether the object 20 is close to the capacitive sensor 10.

However, the conventional capacitive sensing device has the disadvantage that an additional use of the buffer 11 is required, which increases the hardware cost.

Accordingly, a first object of the present invention is to provide a capacitive sensing system that does not require the use of an additional buffer.

The capacitive sensing system comprises: a capacitive sensing device and a counting device. The capacitive sensing device comprises: a capacitive sensor, and a capacitance reading circuit. The capacitive sensor correspondingly generates a varying induced capacitance according to a distance from an object, and the capacitive sensor has an induction plate and a spacer between the sensing plate and the ground, and the The isolation plate is electrically connected to the induction plate to be short-circuited. The capacitance reading circuit is electrically connected to the capacitive sensor, and the charging and discharging of the capacitive sensor is switched to generate an output signal whose frequency follows the increase and decrease of the induced capacitance. The counting device is electrically connected to the capacitance sensing circuit to receive the output signal and obtain a count value based on the output signal.

Preferably, the capacitance reading circuit comprises: a charging switch, a sampling capacitor, a sampling switch, and a comparator. The charging switch has a first end electrically connected to a bias power supply, a second end electrically connected to the isolation plate, and a control end, the control end being controlled such that the first end and the second end are conductive Switch between non-conductions. The sampling capacitor has a first end that provides a sampling voltage and a second end that is grounded. The sampling switch has a first end electrically connected to the isolation plate, a second end electrically connected to the first end of the sampling capacitor, and a control end, the control end being controlled to have first and second ends thereof Switching between conduction and non-conduction, when the sampling switch is turned on, the charge from the capacitive sensor is moved to the sampling capacitor via the sampling switch to be charged to raise the level of the sampling voltage. The comparator has a non-inverting input electrically connected to the first end of the sampling capacitor to receive the sampling voltage, an inverting input receiving a reference voltage, and an output providing the output signal, and the comparator The sampled voltage and the reference voltage are compared to change the level of the output signal.

Preferably, the capacitance readout circuit further comprises: a delay, a resistor, and a reset switch. The delay is electrically connected to the output of the comparator to receive the output signal, and delays the output signal for a predetermined time to obtain a delayed signal. The resistor has a first end electrically connected to the first end of the sampling capacitor, and a second end. The reset switch has a first end electrically connected to the second end of the resistor, a grounded second end, and a control end electrically connected to the delay to receive the delay signal, and the control end is based on the delay signal The change in the level causes the first and second ends to switch between conducting and non-conducting.

Preferably, the charging switch, the sampling switch, and the resetting switch are all an N-type MOSFET, and the first end is a drain and the second end is a source, the control The end is the gate.

Preferably, the counting device comprises: a clock signal generator, and a logic. The clock signal generator is configured to generate a clock signal having a predetermined period. And the logic device is electrically connected to the output end of the comparator to receive the output signal, is electrically connected to the clock signal generator to receive the clock signal, and performs logical operations on the output signal and the clock signal to obtain the meter Value.

Accordingly, a second object of the present invention is to provide a capacitive sensing device that does not require the use of an additional buffer.

The capacitive sensing device comprises: a capacitive sensor and a capacitance reading circuit. The capacitive sensor correspondingly generates a varying induced capacitance according to a distance from an object, and the capacitive sensor has an induction plate and a spacer between the sensing plate and the ground, and the The isolation plate is electrically connected to the induction plate to be short-circuited. The capacitance reading circuit is electrically connected to the capacitive sensor, and the charging and discharging of the capacitive sensor is switched to generate an output signal whose frequency follows the increase and decrease of the induced capacitance.

Preferably, the capacitance reading circuit comprises: a charging switch, a sampling capacitor, a sampling switch, and a comparator. The charging switch has a first end electrically connected to a bias power supply, a second end electrically connected to the isolation plate, and a control end, the control end being controlled such that the first end and the second end are conductive Switch between non-conductions. The sampling capacitor has a first end that provides a sampling voltage and a second end that is grounded. The sampling switch has a first end electrically connected to the isolation plate, a second end electrically connected to the first end of the sampling capacitor, and a control end, the control end being controlled to have first and second ends thereof Switching between conduction and non-conduction, when the sampling switch is turned on, the charge from the capacitive sensor is moved to the sampling capacitor via the sampling switch to be charged to raise the level of the sampling voltage. The comparator has a non-inverting input electrically connected to the first end of the sampling capacitor to receive the sampling voltage, an inverting input receiving a reference voltage, and an output providing the output signal, and the comparator The sampled voltage and the reference voltage are compared to change the level of the output signal.

Preferably, the capacitance readout circuit further comprises: a delay, a resistor, and a reset switch. The delay is electrically connected to the output of the comparator to receive the output signal, and delays the output signal for a predetermined time to obtain a delayed signal. The resistor has a first end electrically connected to the first end of the sampling capacitor, and a second end. The reset switch has a first end electrically connected to the second end of the resistor, a grounded second end, and a control end electrically connected to the delay to receive the delay signal, and the control end is based on the delay signal The change in the level causes the first and second ends to switch between conducting and non-conducting.

Preferably, the charging switch, the sampling switch, and the resetting switch are all an N-type MOSFET, and the first end is a drain and the second end is a source, the control The end is the gate.

Accordingly, a third object of the present invention is to provide a touch device.

The touch device comprises: a plurality of capacitive sensors, a capacitance readout circuit, and a multiplexer.

Each of the capacitive sensors correspondingly generates a varying inductive capacitance according to a distance from an object, and each of the capacitive inductors has an inductive plate and a spacer between the sensing plate and the ground. And the isolation plate is electrically connected to the induction plate to be short-circuited. The multiplexer is coupled between the plurality of capacitive sensors and the capacitance sensing circuit and is controlled by a control signal to determine that the capacitance sensing circuit is electrically connected to the capacitive sensor. The capacitance readout circuit switches and charges the connected capacitive sensor to generate an output signal whose frequency follows the increase and decrease of the induced capacitance.

Preferably, the capacitance reading circuit comprises: a charging switch, a sampling capacitor, a sampling switch, and a comparator. The charging switch has a first end electrically connected to a bias power supply, a second end electrically connected to the isolation plate, and a control end, the control end being controlled such that the first end and the second end are conductive Switch between non-conductions. The sampling capacitor has a first end that provides a sampling voltage and a second end that is grounded. The sampling switch has a first end electrically connected to the isolation plate, a second end electrically connected to the first end of the sampling capacitor, and a control end, the control end being controlled to have first and second ends thereof Switching between conduction and non-conduction, when the sampling switch is turned on, the charge from the capacitive sensor is moved to the sampling capacitor via the sampling switch to be charged to raise the level of the sampling voltage. The comparator has a non-inverting input electrically connected to the first end of the sampling capacitor to receive the sampling voltage, an inverting input receiving a reference voltage, and an output providing the output signal, and the comparator The sampled voltage and the reference voltage are compared to change the level of the output signal.

Preferably, the capacitance readout circuit further comprises: a delay, a resistor, and a reset switch. The delay is electrically connected to the output of the comparator to receive the output signal, and delays the output signal for a predetermined time to obtain a delayed signal. The resistor has a first end electrically connected to the first end of the sampling capacitor, and a second end. The reset switch has a first end electrically connected to the second end of the resistor, a grounded second end, and a control end electrically connected to the delay to receive the delay signal, and the control end is based on the delay signal The change in the level causes the first and second ends to switch between conducting and non-conducting.

The above and other technical contents, features and advantages of the present invention will be apparent from the following detailed description of FIG.

<Capacitive sensing system>

As shown in FIG. 4, a preferred embodiment of the capacitive sensing system 2 of the present invention is adapted to sense whether an object 20 (such as a palm or a finger) enters a sensing distance, and the capacitive sensing system 2 includes a capacitive sensing device 3. And a counting device 4.

The capacitive sensing device 3 includes a capacitive sensor 31 and a capacitance sensing circuit 32.

The capacitive sensor 31 correspondingly generates a varying induced capacitance according to the distance from the object 20. When the distance is long, the amount of change in the induced capacitance with the distance is very small. When the distance is short, the induced capacitance is The amount of change in the distance is large, and the capacitive sensor 31 has a sensing plate 311, and a shielding plate 312 interposed between the sensing plate and the ground, and the spacer plate 312 is The sensing board 311 is electrically connected to be short-circuited.

Referring to FIG. 5, the inductive capacitance of the capacitive sensor 31 is as follows:

Ctotal=Csg+(Cso//Cog)=Csg+[(Cso×Cog)/(Cso+Cog)]......(Formula 1)

The parameter Ctotal is the inductive capacitance of the capacitive sensor 31, and the parameter Csg is the capacitance between the isolation plate 312 and the ground (due to the short circuit between the isolation plate 312 and the induction plate 311, the induction plate 311 is also formed. The capacitance between the grounds, the parameter Cso is the capacitance between the sensing plate 311 and the object 20, and the parameter Cog is the capacitance between the object 20 and the ground. Since the isolation plate 312 provides the power line to the ground, the sensing plate 311 is provided. The power line then goes up to sense the object 20, so as the object 20 approaches, Cso increases and Ctotal increases.

The capacitance reading circuit 32 is electrically connected to the capacitive sensor 31, and the charging and discharging of the capacitive sensor 31 is switched to generate an output signal Vc whose frequency follows the increase and decrease of the induced capacitance, that is, If the object 20 enters the sensing distance to increase the inductive capacitance, the frequency of the output signal Vc also increases. If the object 20 does not enter the sensing distance and the inductive capacitance is fixed, the frequency of the output signal Vc remains fixed. The capacitance reading circuit 32 includes a charging switch S0, a sampling switch S1, a comparator COMP, a reset switch S2, a resistor Rext, a delay D, and a sampling capacitor CS.

The charging switch S0 has a first end electrically connected to a bias power supply VDD, a second end electrically connected to the isolation plate 312, and a control end controlled by the first end and the second end. Switching between conduction and non-conduction, when the charging switch S0 is turned on, current from the bias power supply VDD is transmitted to the capacitive sensor 31 via the charging switch S0 for charging, when the charging switch S0 is not turned on. Then, the capacitive sensor 31 is stopped from charging.

The sampling capacitor CS has a first end that provides a sampling voltage and a grounded second end.

The sampling switch S1 has a first end electrically connected to the isolation plate 312, a second end electrically connected to the first end of the sampling capacitor CS, and a control end, and the control end is controlled to be first and The second end is switched between conducting and non-conducting. When the sampling switch S1 is turned on, the electric charge from the capacitive sensor 31 is transferred to the sampling capacitor CS via the sampling switch S1 for charging to increase the sampling voltage. When the sampling switch S1 is not turned on, the sampling capacitor CS is stopped. In the further description, as the charging switch S0 and the sampling switch S1 are alternately turned on and off a plurality of times, a plurality of charge-transfers are repeated, so that the sampling capacitor CS gradually accumulates electric charges.

The comparator COMP has a non-inverting input terminal (+) electrically connected to the first end of the sampling capacitor CS to receive the sampling voltage, an inverting input terminal (-) receiving a reference voltage Vref, and a providing The output of the output signal Vc, and the comparator COMP compares the sampling voltage with the reference voltage Vref to change the level of the output signal Vc.

The delay D is electrically connected to the output of the comparator COMP to receive the output signal Vc, and delays the output signal Vc for a predetermined time to obtain a delayed signal.

The resistor Rext has a first end electrically connected to the first end of the sampling capacitor CS, and a second end.

The reset switch S2 has a first end electrically connected to the second end of the resistor Rext, a grounded second end, and a control end electrically connected to the delay D to receive the delay signal, the control end being The change in the level of the delayed signal causes the first and second ends to switch between conducting and non-conducting. When the sampling voltage is greater than the reference voltage Vref, the output signal Vc is at a high level and the delay signal is also at a high level, the reset switch S2 is turned on, and the sampling capacitor CS is supplied with a current through the resistor. Rext and the reset switch S2 flow to the ground to discharge. When the sampling voltage is discharged to be less than the reference voltage Vref, the output signal Vc is at a low level and the delay signal is also at a low level, and the reset switch S2 is turned from non-conducting to non-conducting, then the sampling capacitor CS Stop discharging.

The charging switch S0, the sampling switch S1, and the reset switch S2 are all an N-type MOSFET, and the first end is a drain, the second end is a source, and the control end It is the gate.

As shown in FIG. 6 , the operation timing diagram of the above embodiment is when the object 20 does not enter the sensing distance, wherein the parameters VS0 and VS1 are respectively control signals for controlling whether the charging switch S0 and the sampling switch S1 are turned on, and substantially Complementary, the parameter Vb is the sampling voltage, the parameter Vc is the output signal, and the parameter VS2 is the delayed signal.

As shown in FIG. 7 , when the object 20 enters the sensing distance, the operation timing chart of the above embodiment, comparing FIG. 6 and FIG. 7 , it can be seen that when the object 20 enters the sensing distance, the sampling voltage is pulled up rapidly. Up to the reference voltage Vref, but with a higher frequency.

The counting device 4 is electrically connected to the capacitance reading circuit 32 to receive the output signal Vc, and obtains a count value according to the output signal Vc, and the counting device 4 has a clock signal generator 41, and a logic (AND) 42.

The clock signal generator 41 is configured to generate a clock signal Clock having a predetermined period.

And the logic device 42 is electrically connected to the output end of the comparator COMP to receive the output signal, is electrically connected to the clock signal generator 41 to receive the clock signal Clock, and performs the logic signal and the clock signal Clock. Operate to get the count value. Referring to Figures 8 and 9, respectively, is a two-counter diagram when the object 20 does not enter the sensing distance and has an inductive distance. It can be seen that when the object 20 enters the sensing distance, it is in a fixed range scan window. , its count value becomes larger.

<First Preferred Embodiment of Touch Device>

As shown in FIG. 10, the first preferred embodiment of the touch device 5 of the present invention is applicable to a small touch panel, and the touch device 5 includes a plurality of capacitive sensors 31, a multiplexer M, and a Capacitance readout circuit 32.

Each of the capacitive sensors 31 correspondingly generates a varying inductive capacitance according to the distance from an object, and referring to FIG. 5, each of the capacitive sensors 31 has an inductive plate 311, and an inductive plate A spacer 312 is disposed between the ground and the ground, and the spacer 312 is electrically connected to the sensing board 311 to be short-circuited.

The multiplexer M is connected between the plurality of capacitive sensors 31 and the capacitance sensing circuit 32, and is controlled by a control signal to determine which capacitive sensing the capacitance reading circuit 32 is electrically connected to. Device.

The capacitance reading circuit 32 switches and charges the connected capacitive sensor 31 to generate an output signal whose frequency follows the increase and decrease of the induced capacitance. Further, the capacitance reading circuit 32 operates and the detailed components are the same as the capacitive sensing system 2 described above, and therefore will not be described again.

<Second preferred embodiment of touch device>

As shown in FIG. 11 , the second preferred embodiment of the touch device 6 of the present invention is suitable for a large touch panel to improve the sensing performance, and the touch device 6 includes a plurality of capacitive sensors 31 and a multiplexer. M, and a plurality of capacitance reading circuits 32.

Each of the capacitive sensors 31 correspondingly generates a varying inductive capacitance according to the distance from an object, and referring to FIG. 5, each of the capacitive sensors 31 has an inductive plate, and an inductive plate is interposed therebetween. A spacer between the ground, and the spacer 312 is electrically connected to the sensing board 311 to be short-circuited.

The multiplexer M is connected between the plurality of capacitive sensors 31 and the capacitance sensing circuit 32, and is controlled by a control signal to determine which capacitive reading circuit 32 is electrically connected to which capacitive type. Sensor 31.

Each of the capacitance reading circuits 32 switches and charges the connected capacitive sensor 31 to generate an output signal whose frequency follows the increase and decrease of the induced capacitance. Further, each of the capacitance reading circuits 32 operates and the detailed components are the same as the above-described capacitive sensing system 2, and therefore will not be described again.

In summary, the above embodiment has the following advantages:

The isolation plate 312 and the induction plate 311 are electrically connected to be short-circuited without using an additional buffer, which can reduce the hardware cost.

The above is only the preferred embodiment of the present invention, and the scope of the invention is not limited thereto, that is, the simple equivalent changes and modifications made by the scope of the invention and the description of the invention are All remain within the scope of the invention patent.

2. . . Capacitive sensing system

20. . . object

3. . . Capacitive sensing device

31. . . Capacitive sensor

311. . . Sensor board

312. . . Isolation board

32. . . Capacitance readout circuit

S0. . . Charging switch

S1. . . Sampling switch

S2. . . Reset switch

CS. . . Sampling capacitor

Rext. . . resistance

D. . . Delayer

COMP. . . Comparators

4. . . Counting device

41. . . Clock signal generator

42. . . Logic

Csg. . . Isolation board to ground capacity

Cso. . . Sensing board to object capacitance

Cog. . . Object to ground capacitance

VDD. . . Bias power supply

M. . . Multiplexer

Figure 1 is a schematic view of a conventional proximity capacitive sensor;

2 is a schematic view of a conventional capacitive sensor;

3 is a circuit diagram of a conventional capacitive sensing device;

4 is a circuit diagram of a preferred embodiment of the capacitive sensing system of the present invention;

Figure 5 is a schematic view of the capacitive inductor of the preferred embodiment;

Figure 6 is a first operational timing diagram of the preferred embodiment;

Figure 7 is a second operational timing diagram of the preferred embodiment;

Figure 8 is a first timing chart of the preferred embodiment;

Figure 9 is a second timing chart of the preferred embodiment;

10 is a circuit diagram of a first preferred embodiment of the touch device of the present invention; and

Figure 11 is a circuit diagram of a second preferred embodiment of the touch device of the present invention.

2. . . Capacitive sensing system

20. . . object

3. . . Capacitive sensing device

31. . . Capacitive sensor

311. . . Sensor board

312. . . Isolation board

32. . . Capacitance readout circuit

S0. . . Charging switch

S1. . . Sampling switch

S2. . . Reset switch

CS. . . Sampling capacitor

Rext. . . resistance

D. . . Delayer

COMP. . . Comparators

4. . . Counting device

41. . . Clock signal generator

42. . . Logic

Csg. . . Isolation board to ground capacity

Cso. . . Sensing board to object capacitance

Cog. . . Object to ground capacitance

VDD. . . Bias power supply

Claims (12)

A capacitive sensing system comprising: a capacitive sensing device comprising: a capacitive sensor correspondingly generating a varying inductive capacitance according to a distance from an object, and the capacitive sensor has a sensing plate And a spacer between the sensing board and the ground, and the isolating board is electrically connected to the sensing board to be short-circuited; and a capacitance reading circuit electrically connected to the capacitive sensor and switching to the The capacitive sensor performs charging and discharging to generate an output signal whose frequency follows the increase and decrease of the induced capacitance; and a counting device electrically connected to the capacitance reading circuit to receive the output signal, and according to the output signal Get a count value. According to the capacitive sensing system of claim 1, the capacitance sensing circuit includes: a charging switch having a first end electrically connected to a bias power supply, and an electrical connection to the isolation plate a second end, and a control end, the control end is controlled such that the first and second ends are switched between conducting and non-conducting; a sampling capacitor having a first end providing a sampling voltage and a grounding a sampling switch having a first end electrically connected to the isolation plate, a second end electrically connected to the first end of the sampling capacitor, and a control end, the control end being controlled to be first And switching the second end between conduction and non-conduction; when the sampling switch is turned on, the electric charge from the capacitive sensor is moved to the sampling capacitor via the sampling switch for charging to raise the level of the sampling voltage; and a comparator having a non-inverting input electrically coupled to the first end of the sampling capacitor to receive the sampling voltage, an inverting input receiving a reference voltage, and an output providing the output signal, and the output Comparator comparison The sampling voltage and the reference voltage are sized to change the level of the output signal. According to the capacitive sensing system of claim 2, the capacitance sensing circuit further includes: a delay device electrically connected to the output end of the comparator to receive the output signal, and delaying the output signal by one Presetting time to obtain a delay signal; a resistor having a first end electrically connected to the first end of the sampling capacitor, and a second end; and a reset switch having a second electrically connected to the resistor a first end of the terminal, a second end connected to the ground, and a control end electrically connected to the delay device to receive the delayed signal, wherein the control terminal turns on the first and second ends according to the change of the level of the delayed signal Switch between not conducting. According to the capacitive sensing system of claim 3, the charging switch, the sampling switch, and the resetting switch are all an N-type MOSFET, and the first end is a drain The second end is a source, and the control end is a gate. According to the capacitive sensing system of claim 1, the counting device comprises: a clock signal generator for generating a clock signal having a predetermined period; and a logic circuit electrically connected to the comparison The output of the device receives the output signal, is electrically connected to the clock signal generator to receive the clock signal, and performs a logical operation on the output signal and the clock signal to obtain the count value. A capacitive sensing device comprising: a capacitive sensor correspondingly generating a varying inductive capacitance according to a distance from an object, wherein the capacitive sensor has a sensing plate, and a sensing plate is a spacer between the ground, and the isolating plate is electrically connected to the sensing plate to be short-circuited; and a capacitance reading circuit electrically connected to the capacitive sensor and switchingly charging and discharging the capacitive sensor To generate an output signal whose frequency follows the increase and decrease of the induced capacitance. According to the capacitive sensing device of claim 6, the capacitance sensing circuit includes: a charging switch having a first end electrically connected to a bias power supply, and an electrical connection to the isolation plate a second end, and a control end, the control end is controlled such that the first and second ends are switched between conducting and non-conducting; a sampling capacitor having a first end providing a sampling voltage and a grounding a sampling switch having a first end electrically connected to the isolation plate, a second end electrically connected to the first end of the sampling capacitor, and a control end, the control end being controlled to be first And switching the second end between conduction and non-conduction; when the sampling switch is turned on, the electric charge from the capacitive sensor is moved to the sampling capacitor via the sampling switch for charging to raise the level of the sampling voltage; and a comparator having a non-inverting input electrically coupled to the first end of the sampling capacitor to receive the sampling voltage, an inverting input receiving a reference voltage, and an output providing the output signal, and the output Comparator comparison The sampling voltage and the reference voltage are sized to change the level of the output signal. According to the capacitive sensing device of claim 7, the capacitance sensing circuit further includes: a delay device electrically connected to the output end of the comparator to receive the output signal, and delaying the output signal by one Presetting time to obtain a delay signal; a resistor having a first end electrically connected to the first end of the sampling capacitor, and a second end; and a reset switch having a second electrically connected to the resistor a first end of the terminal, a second end connected to the ground, and a control end electrically connected to the delay device to receive the delayed signal, wherein the control terminal turns on the first and second ends according to the change of the level of the delayed signal Switch between not conducting. According to the capacitive sensing device of claim 8, the charging switch, the sampling switch, and the resetting switch are all an N-type MOSFET, and the first end is a bungee The second end is a source, and the control end is a gate. A touch device includes: a plurality of capacitive sensors, each capacitive sensor correspondingly generating a varying induced capacitance according to a distance from an object, and each capacitive sensor has a sensing plate, And a spacer between the sensing board and the ground, and the isolating board is electrically connected to the sensing board to be short-circuited; a capacitance reading circuit; and a multiplexer connected to the plurality of capacitive sensors and The capacitance reading circuit is controlled by a control signal to determine that the capacitance reading circuit is electrically connected to the capacitive sensor; the capacitance reading circuit is switched to the connected capacitive sensing The device performs charging and discharging to generate an output signal whose frequency follows the increase and decrease of the induced capacitance. According to the touch device of claim 10, the capacitance reading circuit includes: a charging switch having a first end electrically connected to a bias power supply and a second electrically connected to the isolation plate And a control terminal, the control terminal is controlled to switch between the first and second ends between conducting and non-conducting; a sampling capacitor having a first end providing a sampling voltage and a second grounding a sampling switch having a first end electrically connected to the isolation plate, a second end electrically connected to the first end of the sampling capacitor, and a control end, the control end being controlled to be first The second end is switched between conducting and non-conducting. When the sampling switch is turned on, the electric charge from the capacitive sensor is moved to the sampling capacitor via the sampling switch to be charged to raise the level of the sampling voltage; and a comparator having a non-inverting input electrically coupled to the first end of the sampling capacitor to receive the sampling voltage, an inverting input receiving a reference voltage, and an output providing the output signal, and the comparing Comparison Voltage and the reference voltage level to change the magnitude of the output signal. According to the touch device of claim 11, the capacitance readout circuit further includes: a delay device electrically connected to the output end of the comparator to receive the output signal, and delaying the output signal by a pre- Setting a time to obtain a delay signal; a resistor having a first end electrically connected to the first end of the sampling capacitor, and a second end; and a reset switch having a second end electrically connected to the resistor a first end, a grounded second end, and a control end electrically connected to the delay device to receive the delayed signal, the control end is configured to turn on the first and second ends according to a change in the level of the delayed signal Switch between non-conductions.