Capacitor capacitance value measuring circuit and device and universal meter

Abstract

The utility model provides a capacitor capacitance value measuring circuit, a capacitor capacitance value measuring device and a universal meter, and relates to the technical field of electronics, the circuit comprises an impedance selection module, a pulse generation module and a controller; a first output end of the impedance selection module is connected with an input end of the pulse generation module, an input end of the impedance selection module is used for connecting a capacitor to be tested, a control end of the impedance selection module is connected with an output end of the controller, and a second output end of the impedance selection module is connected with an acquisition end of the pulse generation module; the input end of the controller is connected with the output end of the pulse generation module; a to-be-measured capacitor is connected to generate a pulse signal of a preset frequency corresponding to an impedance parameter and a capacitive reactance parameter, then a capacitance value corresponding to the capacitive reactance parameter is determined through the preset frequency, and when the capacitance value exceeds an effective value, a corresponding impedance selection signal is sent to adjust the impedance parameter of an output signal. The obtained capacitance value is adjusted to be within the effective value range, automatic gear shifting is achieved, manual operation is not needed, and use is convenient.

Description

Technical Field

[0001] The utility model relates to the field of electronic technology, and in particular to a capacitance value measuring circuit, a device and a multimeter. Background Art

[0002] In the prior art, a single-chip microcomputer is usually used as the core controller to control a multimeter to measure the capacitance to be measured. Since the display digits of the multimeter are limited and the user does not need some useless display digits to interfere with the user's reading, it is necessary to use different gears corresponding to different capacitance units for different types of capacitors to be measured. However, for some users who are not skilled in operation or have difficulty in operation, they cannot manually shift gears correctly, which easily leads to the measurement of wrong capacitance values. Utility Model Content

[0003] The utility model provides a capacitance value measuring circuit, a device and a multimeter, aiming to solve the technical problem of automatically shifting gears to obtain the effective value of the capacitance value to be measured in the prior art when measuring the capacitance value.

[0004] To achieve the above object, the utility model provides a capacitance value measurement circuit, the capacitance value measurement circuit comprising: an impedance selection module, a pulse generation module and a controller;

[0005] The first output end of the impedance selection module is connected to the input end of the pulse generation module, the input end of the impedance selection module is used to connect the capacitor to be measured, the control end of the impedance selection module is connected to the output end of the controller, the second output end of the impedance selection module is connected to the acquisition end of the pulse generation module, and the input end of the controller is connected to the output end of the pulse generation module;

[0006] The pulse generating module is used to transmit a pulse signal corresponding to a preset frequency to the controller when receiving the first resistance-capacitance signal and the second resistance-capacitance signal generated by the impedance selecting module connected to the capacitor to be measured;

[0007] The controller is used to calculate the preset frequency of the pulse signal to determine the capacitance value of the capacitor to be measured, and when the capacitance value exceeds a preset value range, send an impedance selection signal corresponding to the capacitance value to the impedance selection circuit;

[0008] The impedance selection circuit is used to adjust the impedance parameters of the first resistance-capacitance signal and the second resistance-capacitance signal when receiving the impedance selection signal, so that the capacitance value corresponding to the preset frequency is within the preset value range.

[0009] Optionally, the impedance selection module includes: a first impedance selection unit and a second impedance selection unit;

[0010] The impedance output end of the first impedance selection unit is respectively connected to the input end of the pulse generation module and the first input end of the second impedance selection unit, the output end of the second impedance selection unit is connected to the acquisition end of the pulse generation module, the second input end of the second impedance selection unit is used to connect the capacitor to be measured, and the control ends of the first impedance selection unit and the second impedance selection unit are both connected to the output end of the controller;

[0011] The first impedance selection unit is configured to transmit the first resistance-capacitance signal to the pulse generation module and the second impedance selection unit when the impedance selection signal is received and the second impedance selection unit is connected to the capacitor to be measured;

[0012] The second impedance selection unit is used to transmit the second resistance-capacitance signal to the pulse generation module when receiving the impedance selection signal and the first resistance-capacitance signal;

[0013] The pulse generating module is further configured to generate a pulse signal with a preset duty cycle when receiving the first RC signal and the second RC signal, and repeatedly send the pulse signal with the preset duty cycle to the controller at the preset frequency.

[0014] Optionally, the first impedance selection unit includes: a first resistor to a sixth resistor and a first selection chip, and the output end of the controller includes a first output end, a second output end and a third output end;

[0015] The first end of the first resistor, the first end of the second resistor, the first end of the third resistor, the first end of the fourth resistor, the first end of the fifth resistor and the first end of the sixth resistor are connected to a power supply, the second end of the first resistor is connected to a first input pin of the first selection chip, the second end of the second resistor is connected to a second input pin of the first selection chip, the second end of the third resistor is connected to a third input pin of the first selection chip, the second end of the fourth resistor is connected to a fourth input pin of the first selection chip, the second end of the fifth resistor is connected to a fifth input pin of the first selection chip, and the second end of the sixth resistor is connected to a sixth input pin of the first selection chip; the first control input pin of the first selection chip is connected to a first output end of the controller, the second control input pin of the first selection chip is connected to a second output end of the controller, and the third control input pin of the first selection chip is connected to a third output end of the controller; the output pins of the first selection chip are respectively connected to an input end of the pulse generation module and an input end of the second impedance selection unit.

[0016] Optionally, the second impedance selection unit includes: a seventh resistor to a twelfth resistor and a second selection chip;

[0017] The first end of the seventh resistor, the first end of the eighth resistor, the first end of the ninth resistor, the first end of the tenth resistor, the first end of the eleventh resistor and the first end of the twelfth resistor are connected to the impedance output end of the first impedance selection unit, the second end of the seventh resistor is connected to the first input pin of the second selection chip, the second end of the eighth resistor is connected to the second input pin of the second selection chip, the second end of the ninth resistor is connected to the third input pin of the second selection chip, the second end of the tenth resistor is connected to the fourth input pin of the second selection chip, the second end of the eleventh resistor is connected to the fifth input pin of the second selection chip, and the second end of the twelfth resistor is connected to the sixth input pin of the second selection chip; the first control input pin of the second selection chip is connected to the first output end of the controller, the second control input pin of the second selection chip is connected to the second output end of the controller, and the third control input pin of the second selection chip is connected to the third output end of the controller; the output pins of the second selection chip are respectively connected to the acquisition end of the pulse generation module and the first end of the capacitor to be measured, and the second end of the capacitor to be measured is grounded.

[0018] Optionally, the first resistor, the seventh resistor and the capacitor to be measured form the first resistance-capacitance loop;

[0019] The second resistor, the eighth resistor and the capacitor to be measured form a second resistance-capacitance loop;

[0020] The third resistor, the ninth resistor and the capacitor to be measured form a third resistance-capacitance loop;

[0021] The fourth resistor, the tenth resistor and the capacitor to be measured form a fourth resistance-capacitance loop;

[0022] The fifth resistor, the eleventh resistor and the capacitor to be measured form a fifth resistance-capacitance loop;

[0023] The sixth resistor, the twelfth resistor and the capacitor to be measured form the sixth resistance-capacitance loop;

[0024] The impedance selection module is used to transmit the first RC signal and the second RC signal corresponding to any one branch of the first RC loop to the sixth RC loop to the pulse generation module when the impedance selection signal is received and the capacitor to be measured is connected.

[0025] Optionally, the first resistor is equal to the seventh resistor, the second resistor is equal to the eighth resistor, the third resistor is equal to the ninth resistor, the fourth resistor is equal to the tenth resistor, the fifth resistor is equal to the eleventh resistor, and the sixth resistor is equal to the twelfth resistor.

[0026] Optionally, the resistance values ​​of the first resistor and the second resistor are in a preset multiple relationship, the resistance values ​​of the second resistor and the third resistor are in the preset multiple relationship, the resistance values ​​of the third resistor and the fourth resistor are in the preset multiple relationship, the resistance values ​​of the fourth resistor and the fifth resistor are in the preset multiple relationship, and the resistance values ​​of the fifth resistor and the sixth resistor are in the preset multiple relationship.

[0027] Optionally, the pulse generating module comprises: a first diode, a first capacitor and a pulse generating chip;

[0028] The power supply pin of the pulse generating chip is connected to the power supply; the discharge pin of the pulse generating chip is respectively connected to the anode of the first diode and the first output end of the impedance selection module, the first voltage collection pin and the second voltage collection pin of the pulse generating chip are connected to the second output end of the impedance selection module and the cathode of the first diode, the output pin of the pulse generating chip is respectively connected to the input end of the controller and the first end of the first capacitor, and the second end of the first capacitor is grounded.

[0029] In addition, to achieve the above-mentioned purpose, an embodiment of the present utility model further provides a capacitance measurement device, and the capacitance measurement device adopts the capacitance measurement circuit as described above.

[0030] In addition, to achieve the above-mentioned purpose, an embodiment of the present utility model further provides a multimeter, which adopts the capacitance value measuring device as described above.

[0031] The present utility model provides a capacitance measurement circuit, device and multimeter, wherein the capacitance measurement circuit comprises: an impedance selection module, a pulse generation module and a controller; the first output end of the impedance selection module is connected to the input end of the pulse generation module, the input end of the impedance selection module is used to connect the capacitor to be measured, the control end of the impedance selection module is connected to the output end of the controller, the second output end of the impedance selection module is connected to the acquisition end of the pulse generation module, and the input end of the controller is connected to the output end of the pulse generation module; the pulse generation module is used to transmit a pulse signal corresponding to a preset frequency to the controller when receiving a first resistance-capacitance signal and a second resistance-capacitance signal generated by the impedance selection module connected to the capacitor to be measured; the controller is used to calculate the preset frequency of the pulse signal to determine the capacitance value of the capacitor to be measured, and when the capacitance value exceeds a preset value range, send the impedance selection signal corresponding to the capacitance value to the impedance selection circuit; the impedance selection circuit is used to adjust the impedance parameters of the first resistance-capacitance signal and the second resistance-capacitance signal when receiving the impedance selection signal, so that the capacitance value corresponding to the preset frequency is within the preset value range. The capacitor to be tested is connected through the impedance selection module to generate an output signal with corresponding impedance parameters and capacitive reactance parameters. The pulse sending module generates a pulse signal of a preset frequency based on the output signal. The controller determines the capacitance value corresponding to the capacitive reactance parameter through the preset frequency of the pulse signal, and sends the corresponding impedance selection signal to the impedance selection module when the capacitance value exceeds the effective value to adjust the impedance parameter of the output signal. The automatic feedback effect can adjust the obtained capacitance value to the effective value range, realize automatic shifting, and no manual operation is required, which is easy to use. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a structural connection diagram of the first embodiment of the capacitance measurement circuit of the utility model;

[0033] Figure 2 This is a circuit connection diagram of the second embodiment of the capacitance measurement circuit of the utility model. DETAILED DESCRIPTION

[0034] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0035] The present invention provides a capacitance measurement circuit. Figure 1 , Figure 1 This is a structural connection diagram of the first embodiment of the capacitance measurement circuit of the utility model.

[0036] In this embodiment, the capacitance measurement circuit includes: an impedance selection module 10, a pulse generation module 20 and a controller 30;

[0037] The first output end of the impedance selection module 10 is connected to the input end of the pulse generation module 20, the input end of the impedance selection module 10 is used to connect the capacitance Cx to be measured, the control end of the impedance selection module 10 is connected to the output end of the controller 30, the second output end of the impedance selection module 10 is connected to the acquisition end of the pulse generation module 20, and the input end of the controller 30 is connected to the output end of the pulse generation module 20;

[0038] The pulse generating module 20 is used to transmit a pulse signal corresponding to a preset frequency to the controller 30 when receiving the first resistance-capacitance signal and the second resistance-capacitance signal generated by the impedance selecting module 10 connected to the capacitor Cx to be measured;

[0039] The controller 30 is used to calculate the preset frequency of the pulse signal to determine the capacitance value of the capacitor Cx to be measured, and when the capacitance value exceeds a preset value range, send an impedance selection signal corresponding to the capacitance value to the impedance selection circuit;

[0040] The impedance selection circuit is used to adjust the impedance parameters of the first resistance-capacitance signal and the second resistance-capacitance signal when receiving the impedance selection signal, so that the capacitance value corresponding to the preset frequency is within the preset value range.

[0041] It should be noted that, in the present embodiment, the impedance selection module 10 forms a resistance-capacitance loop after being connected to the capacitor to be measured Cx, and the specific connection mode is that the input end of the impedance selection module 10 is connected to the first end of the capacitor to be measured Cx, and the second end of the capacitor to be measured Cx is grounded. The resistance-capacitance loop can form a first resistance-capacitance signal and a second resistance-capacitance signal, and send them to the pulse generation module 20. Among them, the first resistance-capacitance signal and the second resistance-capacitance signal refer to a pair of signals with impedance parameters and capacitive reactance parameters formed after the impedance selection module 10 is connected to the capacitor to be measured Cx.

[0042] It should be understood that the pulse generating module 20 can generate a pulse signal corresponding to a preset frequency based on the impedance parameters and capacitive reactance parameters corresponding to the received first RC signal and the second RC signal, and send it to the controller 30. The preset frequency of the pulse signal generated by it is related to both the impedance parameters and the capacitive reactance parameters.

[0043] It should be noted that the capacitance value of the capacitor Cx to be measured refers to the effective value of the capacitance of the capacitor Cx to be measured, and the range of the effective value is the preset value range. For example, if the unit of the current capacitance measurement gear is in uF, and the capacitance of the capacitor Cx to be measured is 47000nF, and the effective value range is 0-100, then the controller 30 can automatically shift gears, change the determined preset frequency by changing the impedance parameter, and finally change the determined capacitance value to within the preset value range, that is, 47, the unit corresponds to uF, rather than the capacitance value corresponding to other capacitance units such as 470, 4700, 47000, etc.

[0044] It is easy to understand that the controller 30 can directly determine the frequency of the pulse signal based on the number of pulse signals collected within a preset time, and the impedance parameters of the first RC signal and the second RC signal output by the impedance selection module 10 are also controlled by the impedance selection signal output by the controller 30. Therefore, the controller 30 can obtain the corresponding capacitive reactance parameters, that is, the capacitance value of the capacitor Cx to be measured, based on the known impedance parameters and the preset frequency.

[0045] It should be noted that, in this embodiment, the controller 30 may be a single chip microcomputer. The controller 30 may also output a corresponding impedance selection signal to control the impedance parameter output by the impedance selection module 10, so there is a one-to-one correspondence between the impedance selection signal and the current impedance parameter, and it can also be understood that the controller 30 may determine the impedance parameters of the first RC signal and the second RC signal in the current RC circuit according to the impedance selection signal currently output.

[0046] In a specific implementation, when the impedance selection module 10 is connected to the capacitor Cx to be measured, a complete RC loop is formed, a corresponding first RC signal and a second RC signal are generated, and the first RC signal and the second RC signal are sent to the pulse generation module 20. The pulse sending module generates a pulse signal of a preset frequency corresponding to the capacitive reactance parameter and the impedance parameter according to the capacitive reactance parameter and the impedance parameter of the received first RC signal and the second RC signal, and periodically sends the pulse signal to the controller 30. The controller 30 can calculate the preset frequency of the pulse signal according to the number of pulse signals received within each preset time period. At the same time, since the controller 30 can also determine the impedance parameters of the first RC signal and the second RC signal output by the impedance selection signal currently output, the controller 30 can determine the capacitance value corresponding to the capacitor Cx to be measured in combination with the determined impedance parameters and the preset frequency. After determining the capacitance value of the capacitor Cx to be tested, the controller 30 will also determine whether it is within the preset value range set internally. If the currently determined capacitance value is not within the preset value range, the impedance selection signal corresponding to the currently determined capacitance value is transmitted to the impedance selection circuit to adjust the impedance parameters of the first RC signal and the second RC signal in the RC circuit, thereby adjusting the preset frequency of the pulse signal generated by the pulse generating module 20, and then adjusting the capacitance value determined by the controller 30 to within the preset value range, and finally obtaining the capacitance value of the capacitance unit corresponding to the corresponding gear.

[0047] It is worth noting that by adjusting the impedance parameters and capacitive reactance parameters of the first RC signal and the second RC signal to adjust the preset frequency of the pulse signal, it is also possible to ensure that the preset frequency of the pulse signal is within a reasonable frequency range, so that the number of pulse signals calculated by the controller 30 within the preset time will not be too high, thereby reducing the memory occupancy rate of the controller 30 and reducing the power consumption of the controller 30; at the same time, it also reduces the calculation error rate of the controller 30 and increases the calculation accuracy of the capacitance value.

[0048] The present utility model provides a capacitance measurement circuit, which includes: an impedance selection module, a pulse generation module and a controller; the first output end of the impedance selection module is connected to the input end of the pulse generation module, the input end of the impedance selection module is used to connect the capacitor to be measured, the control end of the impedance selection module is connected to the output end of the controller, the second output end of the impedance selection module is connected to the acquisition end of the pulse generation module, and the input end of the controller is connected to the output end of the pulse generation module; the pulse generation module is used to transmit a pulse signal corresponding to a preset frequency to the controller when receiving a first resistance-capacitance signal and a second resistance-capacitance signal generated by the impedance selection module connected to the capacitor to be measured; the controller is used to calculate the preset frequency of the pulse signal to determine the capacitance value of the capacitor to be measured, and when the capacitance value exceeds a preset value range, send the impedance selection signal corresponding to the capacitance value to the impedance selection circuit; the impedance selection circuit is used to adjust the impedance parameters of the first resistance-capacitance signal and the second resistance-capacitance signal when receiving the impedance selection signal, so that the capacitance value corresponding to the preset frequency is within the preset value range. The capacitor to be tested is connected through the impedance selection module to generate an output signal with corresponding impedance parameters and capacitive reactance parameters. The pulse sending module generates a pulse signal of a preset frequency based on the output signal. The controller determines the capacitance value corresponding to the capacitive reactance parameter through the preset frequency of the pulse signal, and sends the corresponding impedance selection signal to the impedance selection module when the capacitance value exceeds the effective value to adjust the impedance parameter of the output signal. The automatic feedback effect can adjust the obtained capacitance value to the effective value range, realize automatic shifting, and no manual operation is required, which is easy to use.

[0049] Based on the first embodiment of the capacitance measurement circuit described above, a second embodiment of the capacitance measurement circuit of the utility model is proposed. Figure 2 , Figure 2 This is a circuit connection diagram of the second embodiment of the capacitance measurement circuit of the utility model.

[0050] In this embodiment, the impedance selection module 10 includes: a first impedance selection unit 11 and a second impedance selection unit 12;

[0051] The output end of the first impedance selection unit 11 is respectively connected to the input end of the pulse generation module 20 and the first input end of the second impedance selection unit 12, the output end of the second impedance selection unit 12 is connected to the acquisition end of the pulse generation module 20, the second input end of the second impedance selection unit 12 is used to connect the capacitor Cx to be measured, and the control ends of the first impedance selection unit 11 and the second impedance selection unit 12 are both connected to the output end of the controller 30;

[0052] The first impedance selection unit 11 is used to transmit the first resistance-capacitance signal to the pulse generation module 20 and the second impedance selection unit 12 when the impedance selection signal is received and the second impedance selection unit 12 is connected to the capacitor to be measured Cx;

[0053] The second impedance selection unit 12 is used to transmit the second resistance-capacitance signal to the pulse generation module 20 when receiving the impedance selection signal and the first resistance-capacitance signal;

[0054] The pulse generating module 20 is further configured to generate a pulse signal with a preset duty cycle when receiving the first RC signal and the second RC signal, and repeatedly send the pulse signal with the preset duty cycle to the controller 30 at the preset frequency.

[0055] It should be noted that, in this embodiment, the first impedance selection unit 11 and the second impedance selection unit 12 are connected in series to form a cascade structure, and the cascade structure is specifically used to connect to the first end of the capacitor Cx to be measured, and the second end of the capacitor Cx to be measured is grounded, and the three together constitute the above-mentioned resistance-capacitance loop. The input end of the resistance-capacitance loop is connected to the first end of the capacitor Cx to be measured, and is used to input the capacitance parameter; the first output end of the resistance-capacitance loop (the output end of the first impedance selection unit 11) is used to output a first resistance-capacitance signal corresponding to the impedance parameter and the capacitance parameter, and the second output end of the resistance-capacitance loop (the output end of the second impedance selection unit 12) is used to output a second resistance-capacitance signal corresponding to the impedance parameter and the capacitance parameter. Among them, the impedance parameter includes a first impedance parameter corresponding to the first impedance selection unit 11 and a second impedance parameter corresponding to the second impedance selection unit 12, and the first impedance selection unit 11 and the second impedance selection unit 12 are a series structure, so the impedance corresponding to the impedance parameter of the second resistance-capacitance signal output by the second impedance selection unit 12 should include the impedance corresponding to the impedance parameter of the first resistance-capacitance signal output by the first impedance selection unit 11.

[0056] It should be understood that in this embodiment, the pulse generating module 20 can determine the first impedance parameter and the second impedance parameter when receiving the first RC signal and the second RC signal, and determine the input impedance of the first impedance selecting unit 11 and the input impedance of the second impedance selecting unit 12 by the first impedance parameter and the second impedance parameter to determine the duty cycle corresponding to the generated pulse signal. In a specific implementation, due to the limited computing power of the controller 30, some signals with a duty cycle may not be fully received. Therefore, the first impedance selecting unit 11 can be used to control the first impedance parameter and the second impedance parameter to adjust the duty cycle of the pulse signal to the preset duty cycle corresponding to the pulse signal that the controller 30 can stably receive, so as to ensure the stability and accuracy of the operation of the controller 30. In this embodiment, the preset duty cycle can be 50%.

[0057] Further, in this embodiment, the first impedance selection unit 11 includes: a first resistor R1 to a sixth resistor R6 and a first selection chip U1, and the output end of the controller 30 includes a first output end, a second output end and a third output end;

[0058] The first end of the first resistor R1, the first end of the second resistor R2, the first end of the third resistor R3, the first end of the fourth resistor R4, the first end of the fifth resistor R5 and the first end of the sixth resistor R6 are connected to the power supply VCC, the second end of the first resistor R1 is connected to the first input pin of the first selection chip U1, the second end of the second resistor R2 is connected to the second input pin of the first selection chip U1, the second end of the third resistor R3 is connected to the third input pin of the first selection chip U1, the second end of the fourth resistor R4 is connected to the fourth input pin of the first selection chip U1, the second end of the fifth resistor R5 is connected to the fifth input pin of the first selection chip U1, and the second end of the sixth resistor R6 is connected to the sixth input pin of the first selection chip U1; the first control input pin of the first selection chip U1 is connected to the first output end of the controller 30, the second control input pin of the first selection chip U1 is connected to the second output end of the controller 30, and the third control input pin of the first selection chip U1 is connected to the third output end of the controller 30; the output pins of the first selection chip U1 are respectively connected to the input end of the pulse generation module 20 and the input end of the second impedance selection unit 12.

[0059] It should be noted that, in this embodiment, the first selection chip U1 can be regarded as a channel selection switch, which is used to select any one of the first resistor R1 to the sixth resistor R6 to be connected to the second impedance selection unit 12 and the pulse generation module 20, and provide the first impedance parameter of the corresponding first resistance-capacitance signal. Among them, the first resistor R1 to the sixth resistor R6 each corresponds to one of the six output channels, and the on-off state of the connection loop between each output channel and the output pin of the first selection chip U1 is controlled by the impedance selection signal output by the controller 30.

[0060] It should be understood that the impedance selection signal can specifically be three parallel high and low level signals. For example, the specific control logic can be: if the first control input pin to the third control input pin of the first selection chip U1 receives three parallel high and low level signals of "100", then the first input pin connected to the first resistor R1 in the first selection chip U1 is controlled to be connected to the output pin; if the first control input pin to the third control input pin of the first selection chip U1 receives three parallel high and low level signals of "010", then the second input pin connected to the second resistor R2 in the first selection chip U1 is controlled to be connected to the output pin, and the subsequent other connection methods are analogous. Among them, "100" represents that the first control input pin to the third control input pin receive three parallel high and low level impedance selection signals of high level-low level-low level respectively. In this embodiment, the first selection chip U1 can be a CD4051 chip.

[0061] Further, in this embodiment, the second impedance selection unit 12 includes: a seventh resistor R7 to a twelfth resistor R12 and a second selection chip U2;

[0062] The first end of the seventh resistor R7, the first end of the eighth resistor R8, the first end of the ninth resistor R9, the first end of the tenth resistor R10, the first end of the eleventh resistor R11 and the first end of the twelfth resistor R12 are connected to the impedance output end of the first impedance selection unit 11, the second end of the seventh resistor R7 is connected to the first input pin of the second selection chip U2, the second end of the eighth resistor R8 is connected to the second input pin of the second selection chip U2, the second end of the ninth resistor R9 is connected to the third input pin of the second selection chip U2, the second end of the tenth resistor R10 is connected to the fourth input pin of the second selection chip U2, the second end of the eleventh resistor R11 is connected to the fourth input pin of the second selection chip U2, and the second end of the twelfth resistor R12 is connected to the impedance output end of the first impedance selection unit 11. The second end of the resistor R11 is connected to the fifth input pin of the second selection chip U2, and the second end of the twelfth resistor R12 is connected to the sixth input pin of the second selection chip U2; the first control input pin of the second selection chip U2 is connected to the first output end of the controller 30, the second control input pin of the second selection chip U2 is connected to the second output end of the controller 30, and the third control input pin of the second selection chip U2 is connected to the third output end of the controller 30; the output pins of the second selection chip U2 are respectively connected to the acquisition end of the pulse generating module 20 and the first end of the capacitor to be measured Cx, and the second end of the capacitor to be measured Cx is grounded.

[0063] It should be noted that, in this embodiment, the second selection chip U2 can also be regarded as a channel selection switch, which is used to select any one of the seventh resistor R7 to the twelfth resistor R12 to be connected to the pulse generation module 20 and the first impedance selection unit 11, and provide the second impedance parameter of the corresponding second resistance-capacitance signal. Among them, the sixth resistor R6 to the twelfth resistor R12 each correspond to one of the six output channels, and the on-off state of the connection loop between each output channel and the output pin of the second selection chip U2 is controlled by the impedance selection signal output by the controller 30.

[0064] It should be understood that, similar to the above, the signal sent by the controller 30 received by the second selection chip U2 is also an impedance selection signal, and the specific control logic can refer to the control logic of the first selection chip U1. In this embodiment, the second selection chip U2 can also be a CD4051 chip.

[0065] Further, in this embodiment, the first resistor R1, the seventh resistor R7 and the capacitor to be measured Cx form the first resistance-capacitance loop;

[0066] The second resistor R2, the eighth resistor R8 and the capacitor to be measured Cx form a second resistance-capacitance loop;

[0067] The third resistor R3, the ninth resistor R9 and the capacitor to be measured Cx form a third resistance-capacitance loop;

[0068] The fourth resistor R4, the tenth resistor R10 and the capacitor to be measured Cx form a fourth resistance-capacitance loop;

[0069] The fifth resistor R5, the eleventh resistor R11 and the capacitor to be measured Cx form a fifth resistance-capacitance loop;

[0070] The sixth resistor R6, the twelfth resistor R12 and the capacitor to be measured Cx form the sixth resistance-capacitance loop;

[0071] The impedance selection module 10 is used to transmit the first RC signal and the second RC signal corresponding to any one branch of the first RC loop to the sixth RC loop to the pulse generation module 20 when receiving the impedance selection signal and connected to the capacitor Cx to be measured.

[0072] It is easy to understand that the RC loop composed of the first impedance selection unit 11, the second impedance selection unit 12 and the capacitor to be measured Cx can include the first RC loop to the sixth RC loop, that is, there are only six combinations of the first resistor R1-seventh resistor R7-capacitor to be measured Cx, the second resistor R2-eighth resistor R8-capacitor to be measured Cx, the third resistor R3-ninth resistor R9-capacitor to be measured Cx, the fourth resistor R4-tenth resistor R10-capacitor to be measured Cx, the fifth resistor R5-eleventh resistor R11-capacitor to be measured Cx and the sixth resistor R6-twelfth resistor R12-capacitor to be measured Cx. In a specific implementation, the impedance selection signal sent by the controller 30 enables the impedance selection module 10 to output the first RC signal and the second RC signal formed by the corresponding RC loop to the pulse generation module 20 only through the above six combinations, so that the pulse generation module 20 can accurately obtain the required impedance parameters and capacitive reactance parameters.

[0073] Further, in this embodiment, the resistance of the first resistor R1 is equal to that of the seventh resistor R7, the resistance of the second resistor R2 is equal to that of the eighth resistor R8, the resistance of the third resistor R3 is equal to that of the ninth resistor R9, the resistance of the fourth resistor R4 is equal to that of the tenth resistor R10, the resistance of the fifth resistor R5 is equal to that of the eleventh resistor R11, and the resistance of the sixth resistor R6 is equal to that of the twelfth resistor R12.

[0074] It should be noted that, in the present embodiment, in the corresponding RC circuit, if the impedance input by the first impedance selection unit 11 is equal to the impedance input by the second impedance selection unit 12, sending the corresponding first RC signal and the second RC signal can enable the pulse generating module 20 to generate a pulse signal with a preset duty cycle of 50%, thereby ensuring that the controller 30 can stably receive each pulse signal sent.

[0075] Further, in the present embodiment, the resistance values ​​of the first resistor R1 and the second resistor R2 are in a preset multiple relationship, the resistance values ​​of the second resistor R2 and the third resistor R3 are in the preset multiple relationship, the resistance values ​​of the third resistor R3 and the fourth resistor R4 are in the preset multiple relationship, the resistance values ​​of the fourth resistor R4 and the fifth resistor R5 are in the preset multiple relationship, and the resistance values ​​of the fifth resistor R5 and the sixth resistor R6 are in the preset multiple relationship.

[0076] It should be noted that, in the present embodiment, the preset multiple relationship can be a 10-fold relationship, that is, the resistance of the sixth resistor R6 is 10 times that of the fifth resistor R5, 100 times that of the fourth resistor R4, 1000 times that of the third resistor R3, 10000 times that of the second resistor R2, and 100000 times that of the first resistor R1. In this way, when the controller 30 sends an impedance selection signal to the impedance selection module 10 to adjust the impedance parameters of the first RC signal and the second RC signal, the capacitance value finally adjusted and determined will also change with multiples of 10, which conforms to the commonly used decimal reading habits and is convenient for users to read. Correspondingly, the multiple relationship of the resistance values ​​between the seventh resistor R7 and the twelfth resistor R12 should also be the same as that between the first resistor R1 and the sixth resistor R6.

[0077] Further, in this embodiment, the pulse generating module 20 includes: a first diode D1, a first capacitor C1 and a pulse generating chip U3;

[0078] The power supply pin of the pulse generating chip U3 is connected to the power supply VCC; the discharge pin of the pulse generating chip U3 is respectively connected to the anode of the first diode D1 and the first output end of the impedance selection module 10, the first voltage collection pin and the second voltage collection pin of the pulse generating chip U3 are connected to the second output end of the impedance selection module 10 and the cathode of the first diode D1, the output pin of the pulse generating chip U3 is respectively connected to the input end of the controller 30 and the first end of the first capacitor C1, and the second end of the first capacitor C1 is grounded.

[0079] It should be noted that, in this embodiment, the pulse generating chip U3 can be a NE555 chip. The input end of the impedance selection module 10, the second output end of the impedance selection module 10 and the acquisition end of the pulse sending module can be regarded as being at the same connection point, and correspondingly, it can also be understood that the output end of the second impedance selection unit 12, the cathode of the first diode D1, the first voltage acquisition pin of the pulse generating chip U3, the second voltage acquisition pin of the pulse generating chip U3 and the first end of the capacitor Cx to be measured are all at the same connection point.

[0080] It is easy to understand that the discharge end of the pulse generating chip U3 can change the high and low levels based on the voltage values ​​collected by the first voltage collection pin and the second voltage collection pin. The first voltage collection pin and the second voltage collection pin of the pulse generating chip U3 can collect the voltage value between the first end of the capacitor Cx to be measured and the ground line, that is, the voltage value at both ends of the capacitor Cx to be measured. It is easy to understand that when the capacitor Cx to be measured is connected to the resistor-capacitor loop, if the voltage value collected by the first voltage collection pin and the second voltage collection pin is higher than 2 / 3 of the power supply voltage of the power supply VCC, the discharge pin outputs a low-level signal, and the capacitor Cx to be measured is discharged; if the voltage value collected by the first voltage collection pin and the second voltage collection pin is lower than 1 / 3 of the power supply voltage of the power supply VCC, the discharge pin outputs a high-level signal, and the capacitor Cx to be measured is charged, forming an oscillation circuit. The oscillation circuit formed as above can generate high and low level signals of corresponding frequency and duty cycle, that is, a pulse signal of preset frequency and preset duty cycle.

[0081] When the impedance corresponding to the input of the first impedance selection unit 11 and the impedance corresponding to the input of the second impedance unit in the resistor-capacitor loop are the same, the preset duty cycle is 50%, and the preset frequency calculation formula is as follows:

[0082]

[0083] Among them, F is the preset frequency, T is the pulse width of the pulse signal, R X1 is the impedance corresponding to the input of the first impedance selection unit 11 in the RC loop, R X2 is the impedance corresponding to the input of the second impedance selection unit 12 in the RC loop, C X is the capacitance of the capacitor Cx to be measured.

[0084] Among them, the first diode D1 is a fast recovery diode, which is used to reduce the rise and fall time of the high and low level pulse signal voltage; the first capacitor C1 is used to filter the output pulse signal, reduce the peak signal generated by the rise or fall of the pulse signal voltage, and prevent the controller 30 from making misjudgments during the pulse signal acquisition process.

[0085] In addition, to achieve the above-mentioned purpose, an embodiment of the utility model further proposes a capacitance measuring device, which adopts all the technical means of all the embodiments of the capacitance measuring circuit described above, and therefore at least has the beneficial effects brought by all the embodiments of the capacitance measuring circuit described above, which will not be described one by one here.

[0086] In addition, to achieve the above-mentioned purpose, the embodiment of the utility model also proposes a multimeter, which adopts all the technical means of all the embodiments of the capacitance measuring device described above, and therefore at least has the beneficial effects brought by all the embodiments of the capacitance measuring device described above, which will not be repeated here one by one.

[0087] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A capacitance measurement circuit, characterized in that: The capacitance measurement circuit comprises: an impedance selection module, a pulse generation module and a controller; The first output end of the impedance selection module is connected to the input end of the pulse generation module, the input end of the impedance selection module is used to connect the capacitor to be measured, the control end of the impedance selection module is connected to the output end of the controller, the second output end of the impedance selection module is connected to the acquisition end of the pulse generation module, and the input end of the controller is connected to the output end of the pulse generation module; The pulse generating module is used to transmit a pulse signal corresponding to a preset frequency to the controller when receiving the first resistance-capacitance signal and the second resistance-capacitance signal generated by the impedance selecting module connected to the capacitor to be measured; The controller is used to calculate the preset frequency of the pulse signal to determine the capacitance value of the capacitor to be measured, and when the capacitance value exceeds a preset value range, send an impedance selection signal corresponding to the capacitance value to the impedance selection module; The impedance selection module is used to adjust the impedance parameters of the first resistance-capacitance signal and the second resistance-capacitance signal when receiving the impedance selection signal, so that the capacitance value corresponding to the preset frequency is within the preset value range.

2. The capacitance measurement circuit according to claim 1, characterized in that: The impedance selection module includes: a first impedance selection unit and a second impedance selection unit; The impedance output end of the first impedance selection unit is respectively connected to the input end of the pulse generation module and the first input end of the second impedance selection unit, the output end of the second impedance selection unit is connected to the acquisition end of the pulse generation module, the second input end of the second impedance selection unit is used to connect the capacitor to be measured, and the control ends of the first impedance selection unit and the second impedance selection unit are both connected to the output end of the controller; The first impedance selection unit is configured to transmit the first resistance-capacitance signal to the pulse generation module and the second impedance selection unit when the impedance selection signal is received and the second impedance selection unit is connected to the capacitor to be measured; The second impedance selection unit is used to transmit the second resistance-capacitance signal to the pulse generation module when receiving the impedance selection signal and the first resistance-capacitance signal; The pulse generating module is further configured to generate a pulse signal with a preset duty cycle when receiving the first RC signal and the second RC signal, and repeatedly send the pulse signal with the preset duty cycle to the controller at the preset frequency.

3. The capacitance measurement circuit according to claim 2, characterized in that: The first impedance selection unit includes: first to sixth resistors and a first selection chip, and the output end of the controller includes a first output end, a second output end and a third output end; The first end of the first resistor, the first end of the second resistor, the first end of the third resistor, the first end of the fourth resistor, the first end of the fifth resistor and the first end of the sixth resistor are connected to a power supply, the second end of the first resistor is connected to a first input pin of the first selection chip, the second end of the second resistor is connected to a second input pin of the first selection chip, the second end of the third resistor is connected to a third input pin of the first selection chip, the second end of the fourth resistor is connected to a fourth input pin of the first selection chip, the second end of the fifth resistor is connected to a fifth input pin of the first selection chip, and the second end of the sixth resistor is connected to a sixth input pin of the first selection chip; the first control input pin of the first selection chip is connected to a first output end of the controller, the second control input pin of the first selection chip is connected to a second output end of the controller, and the third control input pin of the first selection chip is connected to a third output end of the controller; the output pins of the first selection chip are respectively connected to an input end of the pulse generation module and an input end of the second impedance selection unit.

4. The capacitance measurement circuit according to claim 3, characterized in that: The second impedance selection unit includes: a seventh resistor to a twelfth resistor and a second selection chip; The first end of the seventh resistor, the first end of the eighth resistor, the first end of the ninth resistor, the first end of the tenth resistor, the first end of the eleventh resistor and the first end of the twelfth resistor are connected to the impedance output end of the first impedance selection unit, the second end of the seventh resistor is connected to the first input pin of the second selection chip, the second end of the eighth resistor is connected to the second input pin of the second selection chip, the second end of the ninth resistor is connected to the third input pin of the second selection chip, the second end of the tenth resistor is connected to the fourth input pin of the second selection chip, the second end of the eleventh resistor is connected to the fifth input pin of the second selection chip, and the second end of the twelfth resistor is connected to the sixth input pin of the second selection chip; the first control input pin of the second selection chip is connected to the first output end of the controller, the second control input pin of the second selection chip is connected to the second output end of the controller, and the third control input pin of the second selection chip is connected to the third output end of the controller; the output pins of the second selection chip are respectively connected to the acquisition end of the pulse generation module and the first end of the capacitor to be measured, and the second end of the capacitor to be measured is grounded.

5. The capacitance measurement circuit according to claim 4, characterized in that: The first resistor, the seventh resistor and the capacitor to be measured form a first resistance-capacitance loop; The second resistor, the eighth resistor and the capacitor to be measured form a second resistance-capacitance loop; The third resistor, the ninth resistor and the capacitor to be measured form a third resistance-capacitance loop; The fourth resistor, the tenth resistor and the capacitor to be measured form a fourth resistance-capacitance loop; The fifth resistor, the eleventh resistor and the capacitor to be measured form a fifth resistance-capacitance loop; The sixth resistor, the twelfth resistor and the capacitor to be measured form a sixth resistance-capacitance loop; The impedance selection module is used to transmit the first RC signal and the second RC signal corresponding to any one branch of the first RC loop to the sixth RC loop to the pulse generation module when the impedance selection signal is received and the capacitor to be measured is connected.

6. The capacitance measurement circuit according to claim 4, characterized in that: The first resistor has a resistance value equal to that of the seventh resistor, the second resistor has a resistance value equal to that of the eighth resistor, the third resistor has a resistance value equal to that of the ninth resistor, the fourth resistor has a resistance value equal to that of the tenth resistor, the fifth resistor has a resistance value equal to that of the eleventh resistor, and the sixth resistor has a resistance value equal to that of the twelfth resistor.

7. The capacitance measurement circuit according to claim 4, characterized in that: The resistance values ​​of the first resistor and the second resistor are in a preset multiple relationship, the resistance values ​​of the second resistor and the third resistor are in the preset multiple relationship, the resistance values ​​of the third resistor and the fourth resistor are in the preset multiple relationship, the resistance values ​​of the fourth resistor and the fifth resistor are in the preset multiple relationship, and the resistance values ​​of the fifth resistor and the sixth resistor are in the preset multiple relationship.

8. The capacitance measurement circuit according to claim 1, characterized in that: The pulse generating module comprises: a first diode, a first capacitor and a pulse generating chip; The power supply pin of the pulse generating chip is connected to the power supply; the discharge pin of the pulse generating chip is respectively connected to the anode of the first diode and the first output end of the impedance selection module, the first voltage collection pin and the second voltage collection pin of the pulse generating chip are connected to the second output end of the impedance selection module and the cathode of the first diode, the output pin of the pulse generating chip is respectively connected to the input end of the controller and the first end of the first capacitor, and the second end of the first capacitor is grounded.

9. A capacitance value measuring device, characterized in that: The capacitance value measuring device adopts the capacitance value measuring circuit as described in any one of claims 1-8.

10. A multimeter, characterized in that: The multimeter adopts the capacitance value measuring device as claimed in claim 9.

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