Inductance measuring device

Abstract

The utility model provides an inductance measuring device which comprises a single-chip microcomputer power supply module, a first-stage amplification module, a second-stage amplification module and an element to be measured, the single-chip microcomputer power supply module is connected with the first-stage amplification module, the first-stage amplification module is connected with the second-stage amplification module, and the element to be measured is connected with the first-stage amplification module. The second amplification module comprises a matched resistor module Rg and a feedback resistor module Rf, and the element to be tested is arranged between the matched resistor module Rg and the feedback resistor module Rf and is connected with the matched resistor module Rg and the feedback resistor module Rf in series; a sine wave signal fin (t) input by the single-chip microcomputer power supply module passes through the first-stage amplification module and then Vin is output, a sine wave signal fin (t) passes through the second-stage amplification module and then Vout is output, according to a circuit formula: Vout / Rf + Vin / (Rg + L) = 0, L =-Vin / Vout * Rf-Rg can be obtained, and the inductance value of the element to be measured can be obtained. By adopting the scheme, the precision is high, the impedance precision can reach 0.1%, and under the same precision, the measurement range of the device is larger and is about several u-hundreds of mH.

Description

Technical Field

[0001] The utility model belongs to the technical field of electronic information, and particularly relates to an inductance measuring device. Background Art

[0002] Currently available inductance measurement methods are roughly as follows: 1. Bridge method: Advantages include high accuracy and wide bandwidth when using multiple bridges. Disadvantages include the need for manual balancing and narrow bandwidth when using a single bridge. The measurable frequency range is DC to 300 MHz. 2. Resonance method: Advantages include good measurement accuracy for high-Q circuits. Disadvantages include difficulty in debugging and low accuracy for low impedance measurements. The measurable frequency range is 10 kHz to 70 MHz. 3. Network analysis method: Advantages include a wide frequency range and high accuracy. Disadvantages include a limited range for narrow impedance measurements. The measurable frequency range is 5 Hz and higher. Utility Model Content

[0003] The primary purpose of this utility model is to provide a device for measuring inductance with high accuracy, achieving an impedance accuracy of 0.1%. While maintaining the same accuracy, this device offers a wide measurement range, from a few uH to several hundred mH. Extending the measurement range further allows for measurement, but with reduced accuracy. The device is portable, low-cost, and highly cost-effective.

[0004] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0005] An inductance measuring device, comprising: a single-chip microcomputer power supply module, a first-stage amplification module, a second-stage amplification module, and a component to be measured, wherein the single-chip microcomputer power supply module is connected to the first amplification module, the first-stage amplification module is connected to the second-stage amplification module, the second amplification module comprises: a matching resistor module Rg, and a feedback resistor module Rf, the component to be measured is arranged between the matching resistor module Rg and the feedback resistor module Rf, and is respectively connected in series with the matching resistor module Rg and the feedback resistor module Rf; wherein the sinusoidal wave signal f input to the single-chip microcomputer power supply module is in (t) After passing through the first stage amplification module, the output V in After passing through the second stage amplification module, the output is V out , according to the circuit formula: V out / Rf+V in / (Rg+L)=0, it can be concluded that L=-V in / V out *Rf-Rg, the inductance value of the component under test can be obtained.

[0006] As a preferred solution for the inductance measurement device, the first-stage amplification module includes: a single-chip microcomputer U13, a single-chip microcomputer U14, a resistor R3, a resistor R5, a resistor R8, a resistor R28, a resistor R29, a resistor R30, a resistor R31, a capacitor C4, and a capacitor C5; one end of the single-chip microcomputer power supply module is connected to the third pin of the single-chip microcomputer U14, one end of the resistor R8 is connected to the third pin, the resistor R8 is connected to the ground, the second pin of the single-chip microcomputer U14 is connected to one end of the capacitor C4, the other end of the capacitor C4 is connected to one end of C5, the resistor R5 is connected in parallel with the capacitor C4, and the first pin of the single-chip microcomputer U14 is connected to the third pin respectively. The other end of the capacitor C5, one end of the resistor R29 and one end of the resistor R3 are connected, the other end of the capacitor C4 and one end of the capacitor C5 are also connected to the other end of the resistor R29 and one end of the resistor R28, and the fifth pin of the microcontroller U14 is connected to the ground; the first pin of the microcontroller U13 is connected to one end of the resistor R31, and the other end of the resistor R31 is connected to the ground, the third pin of the microcontroller U13 is respectively connected to the other end of the resistor R3 and one end of the resistor R30, the other end of the resistor R30 is connected to the ground, and the sixth pin of the microcontroller U13 is connected to the other end of the resistor R28.

[0007] As a preferred solution of the inductance measurement device, the second-stage amplification module further includes: the single-chip microcomputer U14, the single-chip microcomputer U15, the P1 terminal interface, the resistor R13, the resistor R16, the resistor R27, the resistor R32, the resistor R34, the resistor R35, the resistor R36, the resistor R40, and the capacitor C7;

[0008] One end of the matching resistance module Rg is respectively connected to the first-stage amplification module and one end of the resistor R13, and the other end of the matching resistance module Rg is respectively connected to one end of the P1 end interface and one end of the resistor R27. The device under test is connected to the P1 end interface, and the other end of the resistor R13 is connected to the other end of the resistor R27. One end of the feedback resistance module Rf is connected to the other end of the P1 end interface, and the other end of the feedback resistance module Rf is respectively connected to one end of the capacitor C7 and one end of the resistor R36. The other end of the capacitor C7 is connected to the microcontroller U The seventh pin of the single-chip microcomputer U15 is connected to one end of the resistor R16, and the resistor R35 is connected in parallel with the capacitor C7; the first pin of the single-chip microcomputer U15 is connected to one end of the resistor R40, and the other end of the resistor R40 is connected to the ground; the third pin of the single-chip microcomputer U15 is respectively connected to the other end of the resistor R16 and one end of the resistor R34, and the other end of the resistor R34 is grounded; the sixth pin of the single-chip microcomputer U15 is connected to one end of the resistor R32, and the other end of the resistor R32 is respectively connected to the other end of the feedback resistor module Rf and one end of the resistor R36.

[0009] As a preferred solution for the inductance measurement device, the matching resistance module Rg includes: an SW2 switch, a resistor R1, a resistor R2, and a resistor R4; the first, second, third, fourth, fifth, and sixth pins of the SW2 switch are all connected to the first-stage amplification module and one end of the resistor R13; the tenth pin of the SW2 switch is connected to one end of the resistor R4, the eleventh pin of the SW2 switch is connected to one end of the resistor R1, and the twelfth pin of the SW2 switch is connected to one end of the resistor R2; the other ends of the resistor R4, the resistor R1, and the resistor R2 are respectively connected to one end of the resistor R27 and one end of the P1 end interface.

[0010] As a preferred solution for the inductance measurement device, the feedback resistor module Rf includes: an SW3 switch, a resistor R6, a resistor R7, a resistor R9, a capacitor C1, and a capacitor C6; the first, second, third, fourth, fifth, and sixth pins of the SW3 switch are all connected to the other end of the P1 end interface and one end of the capacitor C1; the tenth pin of the SW3 switch is connected to one end of the resistor R9, the eleventh pin of the SW3 switch is connected to one end of the resistor R7, and the twelfth pin of the SW3 switch is connected to one end of the resistor R6, and the other ends of the resistors R6, R7, and R9 are respectively connected to the other end of the capacitor C1, one end of the capacitor C7, the other end of the resistor R32, and one end of the resistor R36.

[0011] As a preferred solution for the inductance measurement device, the matching resistance module Rg also includes: a precision resistor R X =500Ω, the precision resistor R X Replace the DUT and connect it to the P1 port. out =-Rf / 500*V in , the exact value of the feedback resistor module Rf can be obtained.

[0012] As a preferred solution for the inductance measurement device, the P1 port is short-circuited, the feedback resistor module Rf is selected to be 5KΩ, the matching resistor module Rg is selected to be 100KΩ, and V out =-Rg / 500*V in , the exact value of 100KΩ of the matching resistance module Rg can be obtained.

[0013] As a preferred solution for the inductance measuring device, the inductance measuring device also includes: a differential module, one end of the differential module is respectively connected to the first amplification module and the second-stage amplification module, and the other end of the differential module is connected to the single-chip microcomputer power supply module, and the differential module is used to prevent the first amplification module and the second-stage amplification module from being strictly virtual short.

[0014] As a preferred solution for the inductance measurement device, the differential module includes: a single chip microcomputer U12, a resistor R14, a resistor R15, a resistor R17, a resistor R19, a resistor R20, a resistor R21, a resistor R22, a resistor R24, a resistor R25, a resistor R26, a resistor R33, a resistor R37, a resistor R38, a resistor R39, a resistor R41, a resistor R46, a resistor R47, a resistor R48, a resistor R49, a capacitor C17, a capacitor C22, a capacitor C25, a capacitor C26, capacitor C27, capacitor C30, capacitor C31, capacitor C32, capacitor C37, capacitor C39, capacitor C40, capacitor C41, capacitor C42, and capacitor C43; the first pin of the single-chip computer U12 is connected to one end of the resistor R33, the other end of the resistor R33 is respectively connected to one end of the resistor R22 and one end of the resistor R14, the other end of the resistor R14 is connected to one end of the resistor R15, and the other end of the resistor R15 is connected to The first terminal of the single-chip microcomputer U12 is connected to the ground, the other end of the resistor R22 is connected to the second pin of the single-chip microcomputer U12, the capacitor C17 is connected to the resistor R22 in parallel, the third pin of the single-chip microcomputer U12 is respectively connected to one end of the resistor R19 and the resistor R20, the other end of the resistor R19 is connected to the ground, the other end of the resistor R20 is connected to the other end of the P1 end interface, the fifth pin of the single-chip microcomputer U12 is respectively connected to one end of the resistor R25 and the resistor R26, the other end of the resistor R25 is connected to the ground, the other end of the resistor R26 is respectively connected to the other end of the resistor R13 and the resistor R27, the sixth pin of the single-chip microcomputer U12 is connected to one end of the resistor R24, the seventh pin of the single-chip microcomputer U12 is connected to one end of the resistor R17, the other ends of the resistor R24 ​​and the resistor R17 are respectively connected to one end of the resistor R21, and the capacitor C22 is connected to the resistor R24 ​​in parallel;One end of the resistor R37 is connected to one end of the capacitor C25, one end of the capacitor C31 and the eighth pin of the single-chip computer U14, respectively; the other end of the resistor R37 is connected to the single-chip computer power supply module; the other ends of the capacitors C25 and C31 are grounded; one end of the resistor R38 is connected to one end of the capacitor C26, one end of the capacitor C39 and the seventh pin of the single-chip computer U13, respectively; the other end of the resistor R38 is connected to the single-chip computer power supply module; the capacitor C 26 and the other end of the capacitor C39 are connected to the ground, one end of the resistor R39 is respectively connected to one end of the capacitor C27, one end of the capacitor C32 and the seventh pin of the single-chip microcomputer U15, the other end of the resistor R39 is connected to the single-chip microcomputer power supply module, the other ends of the capacitors C27 and C32 are connected to the ground, one end of the resistor R41 is respectively connected to one end of the capacitor C30, one end of the capacitor C37 and the eighth pin of the single-chip microcomputer U12, and the other end of the resistor R41 The MCU power supply module is connected to the MCU, and the other ends of the capacitors C30 and C37 are connected to the ground; one end of the resistor R46 is respectively connected to one end of the capacitor C40 and the fourth pin of the MCU U14, and the other end of the resistor R46 is connected to the MCU power supply module, and the other end of the capacitor C40 is connected to the ground; one end of the resistor R47 is respectively connected to one end of the capacitor C41 and the fourth pin of the MCU U13, and the other end of the resistor R47 is connected to the MCU power supply module. The other end of the capacitor C41 is connected to the ground, one end of the resistor R48 is respectively connected to one end of the capacitor C42 and the fourth pin of the single-chip microcomputer U15, the other end of the resistor R48 is connected to the single-chip microcomputer power supply module, the other end of the capacitor C42 is connected to the ground, one end of the resistor R49 is respectively connected to one end of the capacitor C43 and the fourth pin of the single-chip microcomputer U12, the other end of the resistor R49 is connected to the single-chip microcomputer power supply module, and the other end of the capacitor C43 is connected to the ground.

[0015] As a preferred solution for the inductance measuring device, the single-chip power supply module includes: a D / A part, a module body, and an A / D part; the module body includes: a single-chip microcomputer U16, a capacitor C10, a capacitor C11, a capacitor C23, and a capacitor C24, and the A / D part includes: a single-chip microcomputer U17, a capacitor C47, and a capacitor C48; the second pin of the single-chip microcomputer U17 is connected to one end of the capacitor C47, the third pin of the single-chip microcomputer U17 is connected to the ground, the fourth pin of the single-chip microcomputer U17 is connected to the other end of the capacitor C47, the fifth pin of the single-chip microcomputer U17 is respectively connected to one end of the capacitor C48, and the other ends of the resistors R46, R47, R48, and R49, the other end of the capacitor C48 is grounded, and the eighth pin of the single-chip microcomputer U17 is respectively connected to the resistors R37, R48, and R49. The resistor R38, the resistor R39 and the other end of the resistor R41 are connected; the first pin of the single-chip microcomputer U16 is respectively connected to one end of the capacitor C10, one end of the capacitor C23 and the positive electrode VCC end of the D / A part; the second pin of the single-chip microcomputer U16 is respectively connected to the other end of the capacitor C10, the other end of the capacitor C23, one end of the capacitor C24, and one end of the capacitor C11, and then connected to the ground; the third pin of the single-chip microcomputer U16 is respectively connected to the other end of the capacitor C24, the other end of the capacitor C11, the eighth pin of the single-chip microcomputer U17, and the other ends of the resistor R37, the resistor R38, the resistor R39 and the resistor R41; the negative pole of the D / A part is connected to the ground, and the input end of the D / A part is connected to the first amplification module.

[0016] The beneficial effects of the utility model are:

[0017] In the present invention, an inductance measuring device is provided, comprising: a single-chip power supply module, a first-stage amplification module, a second-stage amplification module, and a component to be measured, wherein the single-chip power supply module is connected to the first amplification module, the first-stage amplification module is connected to the second-stage amplification module, the second amplification module comprises: a matching resistor module Rg, and a feedback resistor module Rf, the component to be measured is arranged between the matching resistor module Rg and the feedback resistor module Rf, and is respectively connected in series with the matching resistor module Rg and the feedback resistor module Rf; the sinusoidal wave signal f is input to the single-chip power supply module in (t) After passing through the first stage amplification module, the output V in The second stage amplifier module outputs V out , according to the circuit formula: V out / Rf+V in / (Rg+L)=0, it can be concluded that L=-V in / V out*Rf - Rg, ​​the inductance value of the component under test can be obtained. This solution offers high accuracy, with impedance accuracy reaching 0.1%. At the same accuracy, this device has a wide measurement range, from a few uH to several hundred mH. Extending the measurement range also allows for measurement, but accuracy will decrease. It is portable, low-cost, and highly cost-effective. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without creative work, and all of them belong to the protection scope of the present invention, among which:

[0019] Figure 1 This is a schematic diagram of the inductance measuring device of the utility model;

[0020] Figure 2 yes Figure 2 The circuit diagram of the first-stage amplification module, the second-stage amplification module, the matching resistance module Rg, and the feedback electronic module Rf of the inductance measurement device shown;

[0021] Figure 3 yes Figure 2 The circuit diagram of the differential module of the inductance measurement device shown;

[0022] Figure 4 yes Figure 2 The circuit diagram of the microcontroller power supply module of the inductance measurement device is shown. DETAILED DESCRIPTION

[0023] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0024] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but rather merely represents selected embodiments of the present invention. It should be noted that, unless there is a conflict, the various features of the embodiments of the present invention may be combined with each other, and the combined embodiments are still within the scope of protection of the present invention.

[0025] It should also be noted that, in the description of this utility model, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections, electrical connections; direct connections, indirect connections through an intermediate medium, and internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this utility model based on the specific circumstances.

[0026] Currently available inductance measurement methods are roughly as follows: 1. Bridge method: Advantages include high accuracy and wide bandwidth when using multiple bridges. Disadvantages include the need for manual balancing and narrow bandwidth when using a single bridge. The measurable frequency range is DC to 300 MHz. 2. Resonance method: Advantages include good measurement accuracy for high-Q circuits. Disadvantages include difficulty in debugging and low accuracy for low impedance measurements. The measurable frequency range is 10 kHz to 70 MHz. 3. Network analysis method: Advantages include a wide frequency range and high accuracy. Disadvantages include a limited range for narrow impedance measurements. The measurable frequency range is 5 Hz and higher.

[0027] like Figure 1 、 Figure 2 、 Figure 3 and Figure 4 As shown, an embodiment of the present invention provides an inductance measuring device, which includes: a single-chip microcomputer power supply module, a first-stage amplification module, a second-stage amplification module, and a device under test, wherein the single-chip microcomputer power supply module is connected to the first amplification module, the first-stage amplification module is connected to the second-stage amplification module, the second amplification module includes: a matching resistor module Rg and a feedback resistor module Rf, and the device under test is arranged between the matching resistor module Rg and the feedback resistor module Rf and is connected in series with the matching resistor module Rg and the feedback resistor module Rf respectively;

[0028] The sine wave signal f input by the single chip power supply module is in (t) After passing through the first stage amplification module, the output V in After passing through the second stage amplification module, the output is V out , according to the circuit formula: V out / Rf+V in / (Rg+L)=0, it can be concluded that L=-V in / V out *Rf-Rg, the inductance value of the component under test can be obtained.

[0029] The present invention adopts the above-mentioned solution, achieving high accuracy, with impedance accuracy reaching 0.1%. At the same accuracy, the device has a wide measurement range, ranging from a few uH to several hundred mH. Extending the measurement range further would also allow measurement, but accuracy would decrease. The device is portable, low-cost, and highly cost-effective.

[0030] Furthermore, the first-stage amplification module includes: a single-chip microcomputer U13, a single-chip microcomputer U14, a resistor R3, a resistor R5, a resistor R8, a resistor R28, a resistor R29, a resistor R30, a resistor R31, a capacitor C4, and a capacitor C5;

[0031] One end of the single-chip microcomputer power supply module is connected to the third pin of the single-chip microcomputer U14, one end of the resistor R8 is connected to the third pin, the resistor R8 is connected to the ground, the second pin of the single-chip microcomputer U14 is connected to one end of the capacitor C4, the other end of the capacitor C4 is connected to one end of C5, the resistor R5 is connected in parallel with the capacitor C4, the first pin of the single-chip microcomputer U14 is respectively connected to the other end of the capacitor C5, one end of the resistor R29 and one end of the resistor R3, the other end of the capacitor C4 and one end of the capacitor C5 are also connected to the other end of the resistor R29 and one end of the resistor R28, and the fifth pin of the single-chip microcomputer U14 is connected to the ground;

[0032] The first pin of the microcontroller U13 is connected to one end of the resistor R31, the other end of the resistor R31 is connected to the ground, the third pin of the microcontroller U13 is respectively connected to the other end of the resistor R3 and one end of the resistor R30, the other end of the resistor R30 is connected to the ground, and the sixth pin of the microcontroller U13 is connected to the other end of the resistor R28.

[0033] Furthermore, the second-stage amplification module further includes: the single-chip microcomputer U14, the single-chip microcomputer U15, the P1 terminal interface, the resistor R13, the resistor R16, the resistor R27, the resistor R32, the resistor R34, the resistor R35, the resistor R36, the resistor R40, and the capacitor C7;

[0034] One end of the matching resistor module Rg is connected to the first-stage amplification module and one end of the resistor R13, respectively. The other end of the matching resistor module Rg is connected to one end of the P1 interface and one end of the resistor R27, respectively. The DUT is connected to the P1 interface, and the other end of the resistor R13 is connected to the other end of the resistor R27.

[0035] One end of the feedback resistor module Rf is connected to the other end of the P1 interface, and the other end of the feedback resistor module Rf is respectively connected to one end of the capacitor C7 and one end of the resistor R36. The other end of the capacitor C7 is connected to the seventh pin of the single-chip computer U14 and one end of the resistor R16. The resistor R35 is connected in parallel with the capacitor C7.

[0036] The first pin of the single-chip microcomputer U15 is connected to one end of the resistor R40, the other end of the resistor R40 is connected to the ground, the third pin of the single-chip microcomputer U15 is respectively connected to the other end of the resistor R16 and one end of the resistor R34, the other end of the resistor R34 is grounded, the sixth pin of the single-chip microcomputer U15 is connected to one end of the resistor R32, the other end of the resistor R32 is respectively connected to the other end of the feedback resistor module Rf and one end of the resistor R36.

[0037] Furthermore, the matching resistor module Rg includes: a switch SW2, a resistor R1, a resistor R2, and a resistor R4;

[0038] The first, second, third, fourth, fifth, and sixth pins of the SW2 switch are all connected to the first-stage amplification module and one end of the resistor R13;

[0039] The tenth pin of the SW2 switch is connected to one end of the resistor R4, the eleventh pin of the SW2 switch is connected to one end of the resistor R1, the twelfth pin of the SW2 switch is connected to one end of the resistor R2, and the other ends of the resistor R4, the resistor R1, and the resistor R2 are respectively connected to one end of the resistor R27 and one end of the P1 end interface.

[0040] Furthermore, the feedback resistance module Rf includes: a switch SW3, a resistor R6, a resistor R7, a resistor R9, a capacitor C1, and a capacitor C6;

[0041] The first, second, third, fourth, fifth, and sixth pins of the SW3 switch are connected to the other end of the P1 interface and one end of the capacitor C1;

[0042] The tenth pin of the SW3 switch is connected to one end of the resistor R9, the eleventh pin of the SW3 switch is connected to one end of the resistor R7, and the twelfth pin of the SW3 switch is connected to one end of the resistor R6. The other ends of the resistors R6, R7, and R9 are respectively connected to the other end of the capacitor C1, one end of the capacitor C7, the other end of the resistor R32, and one end of the resistor R36.

[0043] Furthermore, the matching resistor module Rg also includes: a precision resistor RX =500Ω, the precision resistor R X Replace the DUT and connect it to the P1 port. out =-Rf / 500*V in , the exact value of the feedback resistor module Rf can be obtained.

[0044] Furthermore, the P1 port is short-circuited, the feedback resistor module Rf is selected to be 5KΩ, the matching resistor module Rg is selected to be 100KΩ, and the V out =-Rg / 500*V in , the exact value of 100KΩ of the matching resistance module Rg can be obtained.

[0045] Furthermore, the inductance measuring device also includes: a differential module, one end of the differential module is respectively connected to the first amplification module and the second-stage amplification module, and the other end of the differential module is connected to the single-chip microcomputer power supply module, and the differential module is used to prevent the first amplification module and the second-stage amplification module from being strictly virtual short.

[0046] Furthermore, the differential module includes: a single chip computer U12, a resistor R14, a resistor R15, a resistor R17, a resistor R19, a resistor R20, a resistor R21, a resistor R22, a resistor R24, a resistor R25, a resistor R26, a resistor R33, a resistor R37, a resistor R38, a resistor R39, a resistor R41, a resistor R46, a resistor R47, a resistor R48, a resistor R49, a capacitor C17, a capacitor C22, a capacitor C25, a capacitor C26, a capacitor C27, a capacitor C30, a capacitor C31, a capacitor C32, a capacitor C37, a capacitor C39, a capacitor C40, a capacitor C41, a capacitor C42, and a capacitor C43;

[0047] The first pin of the single-chip microcomputer U12 is connected to one end of the resistor R33, the other end of the resistor R33 is respectively connected to one end of the resistor R22 and one end of the resistor R14, the other end of the resistor R14 is connected to one end of the resistor R15, the other end of the resistor R15 is connected to the ground, the other end of the resistor R22 is connected to the second pin of the single-chip microcomputer U12, the capacitor C17 is connected in parallel with the resistor R22, the third pin of the single-chip microcomputer U12 is respectively connected to one end of the resistor R19 and the resistor R20, the other end of the resistor R19 is connected to the ground, the other end of the resistor R20 is connected to the ground. One end is connected to the other end of the P1 end interface, the fifth pin of the single-chip microcomputer U12 is respectively connected to one end of the resistor R25 and the resistor R26, the other end of the resistor R25 is connected to the ground, the other end of the resistor R26 is respectively connected to the other end of the resistor R13 and the resistor R27, the sixth pin of the single-chip microcomputer U12 is connected to one end of the resistor R24, the seventh pin of the single-chip microcomputer U12 is connected to one end of the resistor R17, the other ends of the resistor R24 ​​and the resistor R17 are respectively connected to one end of the resistor R21, and the capacitor C22 is connected in parallel with the resistor R24;

[0048] One end of the resistor R37 is connected to one end of the capacitor C25, one end of the capacitor C31 and the eighth pin of the single-chip microcomputer U14 respectively, the other end of the resistor R37 is connected to the single-chip microcomputer power supply module, the other ends of the capacitors C25 and C31 are connected to the ground, one end of the resistor R38 is connected to one end of the capacitor C26, one end of the capacitor C39 and the seventh pin of the single-chip microcomputer U13 respectively, the other end of the resistor R38 is connected to the single-chip microcomputer power supply module, the other ends of the capacitors C26 and C39 are connected to the ground. , one end of the resistor R39 is respectively connected to one end of the capacitor C27, one end of the capacitor C32 and the seventh pin of the single-chip microcomputer U15, the other end of the resistor R39 is connected to the single-chip microcomputer power supply module, the other ends of the capacitors C27 and C32 are connected to the ground, one end of the resistor R41 is respectively connected to one end of the capacitor C30, one end of the capacitor C37 and the eighth pin of the single-chip microcomputer U12, the other end of the resistor R41 is connected to the single-chip microcomputer power supply module, and the other ends of the capacitors C30 and C37 are connected to the ground;

[0049] One end of the resistor R46 is respectively connected to one end of the capacitor C40 and the fourth pin of the single-chip microcomputer U14, the other end of the resistor R46 is connected to the single-chip microcomputer power supply module, the other end of the capacitor C40 is connected to the ground, one end of the resistor R47 is respectively connected to one end of the capacitor C41 and the fourth pin of the single-chip microcomputer U13, the other end of the resistor R47 is connected to the single-chip microcomputer power supply module, the other end of the capacitor C41 is connected to the ground, one end of the resistor R48 is respectively connected to one end of the capacitor C42 and the fourth pin of the single-chip microcomputer U15, the other end of the resistor R48 is connected to the single-chip microcomputer power supply module, the other end of the capacitor C42 is connected to the ground, one end of the resistor R49 is respectively connected to one end of the capacitor C43 and the fourth pin of the single-chip microcomputer U12, the other end of the resistor R49 is connected to the single-chip microcomputer power supply module, and the other end of the capacitor C43 is connected to the ground.

[0050] Furthermore, the single chip microcomputer power supply module includes: a D / A part, a module body, and an A / D part;

[0051] The module body includes: single chip microcomputer U16, capacitor C10, capacitor C11, capacitor C23, and capacitor C24; the A / D part includes: single chip microcomputer U17, capacitor C47, and capacitor C48;

[0052] The second pin of the single-chip microcomputer U17 is connected to one end of the capacitor C47, the third pin of the single-chip microcomputer U17 is connected to the ground, the fourth pin of the single-chip microcomputer U17 is connected to the other end of the capacitor C47, the fifth pin of the single-chip microcomputer U17 is respectively connected to one end of the capacitor C48 and the other ends of the resistors R46, R47, R48 and R49, the other end of the capacitor C48 is grounded, and the eighth pin of the single-chip microcomputer U17 is respectively connected to the other ends of the resistors R37, R38, R39 and R41;

[0053] The first pin of the single-chip microcomputer U16 is respectively connected to one end of the capacitor C10, one end of the capacitor C23, and the positive electrode VCC end of the D / A part; the second pin of the single-chip microcomputer U16 is respectively connected to the other end of the capacitor C10, the other end of the capacitor C23, one end of the capacitor C24, and one end of the capacitor C11, and then connected to the ground; the third pin of the single-chip microcomputer U16 is respectively connected to the other end of the capacitor C24, the other end of the capacitor C11, the eighth pin of the single-chip microcomputer U17, and the other ends of the resistors R37, R38, R39, and R41;

[0054] The negative electrode of the D / A part is connected to the ground, and the input end of the D / A part is connected to the first amplification module.

[0055] The basic principles of this utility model are as follows:

[0056] The single chip power supply module generates the input signal f through the D / A part in (t)=V0sinwt is amplified into Vin through the first stage. This stage is a pure resistance circuit, which amplifies the amplitude and improves the signal current drive.

[0057] The matching resistor and the device under test form the input resistor of the second stage amplifier, and together with the feedback resistor, they form an amplifier loop. This loop is the main measurement circuit. Rf and Rg can be accurately calibrated. out After differential module processing, it is transmitted to the module body through the A / D module. Because both input and output waveforms are processed by the same module body, the changed amplitude and phase values ​​can be calculated. Thus, V in / V out .

[0058] By formula: L = -V in / V out *Rf-Rg, the inductance value of the component under test can be calculated.

[0059] The function of the differential module is to prevent the amplifier from being strictly virtual short, that is, the positive pole of the second stage amplifier is grounded and the negative pole V - Theoretically, it should also be 0, but in reality there may be a little voltage. Using differential signals to eliminate this error can improve accuracy. out With V - Form a pair of differential, V in With V - form a pair of differences.

[0060] The specific test principles are as follows:

[0061] like Figure 1 、 Figure 2 、 Figure 3 and Figure 4 As shown, the input sine wave signal f in (t) Enter from the RF1 interface. MCU U14 and MCU U13 form the first stage amplification module. SW2 switch controls the selection of the resistance value of the matching resistor module Rg (R1, R2, R4). SW3 switch controls the selection of the resistance value of the feedback resistor module Rf (R6, R7, R9). The P1 port receives the component under test. Among them, the matching resistor module Rg, the component under test and the feedback resistor module Rf, as well as MCU U14 and MCU U15 form the second stage amplification module. The input signal f in(t) After passing through the two-stage amplification module, it is output from the terminal V1_OUT, namely the RF2 interface.

[0062] According to the circuit formula:

[0063] V out / Rf+V in / (Rg+L)=0 (1)

[0064] Where V out = is the voltage at V1_OUT. Considering the measurement accuracy, there may be error voltage at the positive and negative inputs of the microcontroller U14. out is the differential voltage between V1_OUT and A1. Similarly, V in is the differential voltage between A2 and A1. Rf and Rg are controlled by switches SW2 and SW3 respectively. It can be calculated that:

[0065] L=-V in / V out *Rf-Rg (2)

[0066] The specific data processing principles are as follows:

[0067] Get the voltage V through the differential module out 、V in , transmitted to the module body through A / D conversion, and the following two steps are programmed in the module body to obtain the amplitude and phase of the output voltage, thereby calculating the L value:

[0068] Since the input signal fin(t) is generated by the module itself, the unit amplitude square wave with 0 degree phase and 90 degree phase can also be generated by the microcontroller. Assuming fin(t) = V0sinwt, then V in =k1*V0sinwt, V out =k2*V0sin(wt+α).

[0069] 1. V in Multiplying it with a unit amplitude square wave with a phase of 0 degrees gives the output average value V1:

[0070] V1=k*V0cosα (3)

[0071] 2. V in Multiplying it with a unit amplitude square wave with a 90-degree phase gives the output average value V2:

[0072] V2=k*V0sinα (4)

[0073] From (3) and (4), we can get

[0074] |V|=Vave=(V1 2 +V22 ) 1 / 2

[0075] α=tan -1 (V2 / V1)

[0076] In this way, the amplitude and phase of any signal can be calculated. in / V out , calculate the inductance value.

[0077] The principle of specific accuracy calibration is as follows:

[0078] Based on the above principles and algorithms, measurement accuracy depends on the accuracy of the feedback resistor module Rf and the matching resistor module Rg, as well as the sampling accuracy of the A / D circuit. This accuracy depends on the hardware performance of the module itself, and a sampling rate of 1 Mbps is sufficient for our use. To achieve the other accuracy, we simply need to purchase a high-precision resistor Rx = 500Ω and perform impedance calibration.

[0079] In this calibration, the P1 port is connected to a high-precision resistor Rx. out The formula is:

[0080] V out =-Rf / 500*V in

[0081] This calibration is used to calculate the exact value of the feedback resistor block Rf for both the 100Ω and 5kΩ settings.

[0082] Then short-circuit the P1 port, select 5kΩ for the feedback resistor module Rf, and 100kΩ for the matching resistor module Rg. The exact value of 5kΩ has already been calculated using the above formula, so the exact value of 100kΩ can be calculated using the same formula. Therefore, all high-precision resistance values ​​can be calculated by simply purchasing a 500Ω high-precision resistor.

[0083] The present invention is described in detail above with reference to the accompanying drawings, but the present invention is not limited to the embodiments described. It is apparent to those skilled in the art that various changes, modifications, substitutions, and variations to these embodiments may be made without departing from the principles and spirit of the present invention, and these changes and modifications still fall within the scope of protection of the present invention.

Claims

1. An inductance measuring device, characterized in that: include: A single-chip microcomputer power supply module, a first-stage amplification module, a second-stage amplification module, and a device under test, wherein the single-chip microcomputer power supply module is connected to the first-stage amplification module, the first-stage amplification module is connected to the second-stage amplification module, the second-stage amplification module includes: a matching resistor module Rg and a feedback resistor module Rf, and the device under test is arranged between the matching resistor module Rg and the feedback resistor module Rf and is respectively connected in series with the matching resistor module Rg and the feedback resistor module Rf; The sine wave signal f input by the single chip power supply module is in (t) After passing through the first stage amplification module, the output V in After passing through the second stage amplification module, the output is V out , according to the circuit formula: V out / Rf+V in / (Rg+L)=0, it can be concluded that L=-V in / V out *Rf-Rg, the inductance value of the component under test can be obtained.

2. The inductance measuring device according to claim 1, wherein: The first-stage amplification module includes: a single-chip microcomputer U13, a single-chip microcomputer U14, a resistor R3, a resistor R5, a resistor R8, a resistor R28, a resistor R29, a resistor R30, a resistor R31, a capacitor C4, and a capacitor C5; One end of the single-chip microcomputer power supply module is connected to the third pin of the single-chip microcomputer U14, one end of the resistor R8 is connected to the third pin, the resistor R8 is connected to the ground, the second pin of the single-chip microcomputer U14 is connected to one end of the capacitor C4, the other end of the capacitor C4 is connected to one end of C5, the resistor R5 is connected in parallel with the capacitor C4, the first pin of the single-chip microcomputer U14 is respectively connected to the other end of the capacitor C5, one end of the resistor R29 and one end of the resistor R3, the other end of the capacitor C4 and one end of the capacitor C5 are also connected to the other end of the resistor R29 and one end of the resistor R28, and the fifth pin of the single-chip microcomputer U14 is connected to the ground; The first pin of the microcontroller U13 is connected to one end of the resistor R31, the other end of the resistor R31 is connected to the ground, the third pin of the microcontroller U13 is respectively connected to the other end of the resistor R3 and one end of the resistor R30, the other end of the resistor R30 is connected to the ground, and the sixth pin of the microcontroller U13 is connected to the other end of the resistor R28.

3. The inductance measuring device according to claim 2, wherein: The second stage amplification module further includes: the single chip microcomputer U14, the single chip microcomputer U15, the P1 terminal interface, the resistor R13, the resistor R16, the resistor R27, the resistor R32, the resistor R34, the resistor R35, the resistor R36, the resistor R40, and the capacitor C7; One end of the matching resistor module Rg is connected to the first-stage amplification module and one end of the resistor R13, respectively. The other end of the matching resistor module Rg is connected to one end of the P1 interface and one end of the resistor R27, respectively. The DUT is connected to the P1 interface, and the other end of the resistor R13 is connected to the other end of the resistor R27. One end of the feedback resistor module Rf is connected to the other end of the P1 interface, and the other end of the feedback resistor module Rf is respectively connected to one end of the capacitor C7 and one end of the resistor R36. The other end of the capacitor C7 is connected to the seventh pin of the single-chip computer U14 and one end of the resistor R16. The resistor R35 is connected in parallel with the capacitor C7. The first pin of the single-chip microcomputer U15 is connected to one end of the resistor R40, the other end of the resistor R40 is connected to the ground, the third pin of the single-chip microcomputer U15 is respectively connected to the other end of the resistor R16 and one end of the resistor R34, the other end of the resistor R34 is grounded, the sixth pin of the single-chip microcomputer U15 is connected to one end of the resistor R32, the other end of the resistor R32 is respectively connected to the other end of the feedback resistor module Rf and one end of the resistor R36.

4. The inductance measuring device according to claim 3, wherein: The matching resistor module Rg includes: a switch SW2, a resistor R1, a resistor R2, and a resistor R4; The first, second, third, fourth, fifth, and sixth pins of the SW2 switch are all connected to the first-stage amplification module and one end of the resistor R13; The tenth pin of the SW2 switch is connected to one end of the resistor R4, the eleventh pin of the SW2 switch is connected to one end of the resistor R1, the twelfth pin of the SW2 switch is connected to one end of the resistor R2, and the other ends of the resistor R4, the resistor R1, and the resistor R2 are respectively connected to one end of the resistor R27 and one end of the P1 terminal interface.

5. The inductance measuring device according to claim 3, wherein: The feedback resistor module Rf includes: switch SW3, resistor R6, resistor R7, resistor R9, capacitor C1, and capacitor C6; The first, second, third, fourth, fifth, and sixth pins of the SW3 switch are connected to the other end of the P1 interface and one end of the capacitor C1; The tenth pin of the SW3 switch is connected to one end of the resistor R9, the eleventh pin of the SW3 switch is connected to one end of the resistor R7, and the twelfth pin of the SW3 switch is connected to one end of the resistor R6. The other ends of the resistors R6, R7, and R9 are respectively connected to the other end of the capacitor C1, one end of the capacitor C7, the other end of the resistor R32, and one end of the resistor R36.

6. The inductance measuring device according to claim 4, wherein: The matching resistor module Rg also includes: a precision resistor R X =500Ω, the precision resistor R X Replace the DUT and connect it to the P1 port. out =-Rf / 500*V in , the exact value of the feedback resistor module Rf can be obtained.

7. The inductance measuring device according to claim 5, wherein: The P1 terminal interface is short-circuited, the feedback resistor module Rf is selected to be 5KΩ, the matching resistor module Rg is selected to be 100KΩ, and the V out =-Rg / 500*V in , the exact value of 100KΩ of the matching resistance module Rg can be obtained.

8. The inductance measuring device according to claim 4, wherein: The inductance measuring device also includes: a differential module, one end of which is respectively connected to the first-stage amplification module and the second-stage amplification module, and the other end of which is connected to the single-chip microcomputer power supply module, and the differential module is used to prevent the first-stage amplification module and the second-stage amplification module from being strictly virtual short.

9. The inductance measuring device according to claim 8, wherein: The differential module includes: a single-chip computer U12, a resistor R14, a resistor R15, a resistor R17, a resistor R19, a resistor R20, a resistor R21, a resistor R22, a resistor R24, a resistor R25, a resistor R26, a resistor R33, a resistor R37, a resistor R38, a resistor R39, a resistor R41, a resistor R46, a resistor R47, a resistor R48, a resistor R49, a capacitor C17, a capacitor C22, a capacitor C25, a capacitor C26, a capacitor C27, a capacitor C30, a capacitor C31, a capacitor C32, a capacitor C37, a capacitor C39, a capacitor C40, a capacitor C41, a capacitor C42, and a capacitor C43; The first pin of the single-chip microcomputer U12 is connected to one end of the resistor R33, the other end of the resistor R33 is respectively connected to one end of the resistor R22 and one end of the resistor R14, the other end of the resistor R14 is connected to one end of the resistor R15, the other end of the resistor R15 is connected to the ground, the other end of the resistor R22 is connected to the second pin of the single-chip microcomputer U12, the capacitor C17 is connected in parallel with the resistor R22, the third pin of the single-chip microcomputer U12 is respectively connected to one end of the resistor R19 and the resistor R20, the other end of the resistor R19 is connected to the ground, the The other end is connected to the other end of the P1 end interface, the fifth pin of the single-chip microcomputer U12 is respectively connected to one end of the resistor R25 and the resistor R26, the other end of the resistor R25 is connected to the ground, the other end of the resistor R26 is respectively connected to the other end of the resistor R13 and the resistor R27, the sixth pin of the single-chip microcomputer U12 is connected to one end of the resistor R24, the seventh pin of the single-chip microcomputer U12 is connected to one end of the resistor R17, the other ends of the resistor R24 ​​and the resistor R17 are respectively connected to one end of the resistor R21, and the capacitor C22 is connected in parallel with the resistor R24; One end of the resistor R37 is connected to one end of the capacitor C25, one end of the capacitor C31 and the eighth pin of the single-chip microcomputer U14 respectively, the other end of the resistor R37 is connected to the single-chip microcomputer power supply module, the other ends of the capacitors C25 and C31 are connected to the ground, one end of the resistor R38 is connected to one end of the capacitor C26, one end of the capacitor C39 and the seventh pin of the single-chip microcomputer U13 respectively, the other end of the resistor R38 is connected to the single-chip microcomputer power supply module, the other ends of the capacitors C26 and C39 are connected to the ground. , one end of the resistor R39 is respectively connected to one end of the capacitor C27, one end of the capacitor C32 and the seventh pin of the single-chip microcomputer U15, the other end of the resistor R39 is connected to the single-chip microcomputer power supply module, the other ends of the capacitors C27 and C32 are connected to the ground, one end of the resistor R41 is respectively connected to one end of the capacitor C30, one end of the capacitor C37 and the eighth pin of the single-chip microcomputer U12, the other end of the resistor R41 is connected to the single-chip microcomputer power supply module, and the other ends of the capacitors C30 and C37 are connected to the ground; One end of the resistor R46 is respectively connected to one end of the capacitor C40 and the fourth pin of the single-chip microcomputer U14, the other end of the resistor R46 is connected to the single-chip microcomputer power supply module, the other end of the capacitor C40 is connected to the ground, one end of the resistor R47 is respectively connected to one end of the capacitor C41 and the fourth pin of the single-chip microcomputer U13, the other end of the resistor R47 is connected to the single-chip microcomputer power supply module, the other end of the capacitor C41 is connected to the ground, one end of the resistor R48 is respectively connected to one end of the capacitor C42 and the fourth pin of the single-chip microcomputer U15, the other end of the resistor R48 is connected to the single-chip microcomputer power supply module, the other end of the capacitor C42 is connected to the ground, one end of the resistor R49 is respectively connected to one end of the capacitor C43 and the fourth pin of the single-chip microcomputer U12, the other end of the resistor R49 is connected to the single-chip microcomputer power supply module, and the other end of the capacitor C43 is connected to the ground.

10. The inductance measuring device according to claim 9, wherein: The single chip microcomputer power supply module includes: a D / A part, a module body, and an A / D part; The module body includes: single chip microcomputer U16, capacitor C10, capacitor C11, capacitor C23, and capacitor C24; the A / D part includes: single chip microcomputer U17, capacitor C47, and capacitor C48; The second pin of the single-chip microcomputer U17 is connected to one end of the capacitor C47, the third pin of the single-chip microcomputer U17 is connected to the ground, the fourth pin of the single-chip microcomputer U17 is connected to the other end of the capacitor C47, the fifth pin of the single-chip microcomputer U17 is respectively connected to one end of the capacitor C48 and the other ends of the resistors R46, R47, R48 and R49, the other end of the capacitor C48 is grounded, and the eighth pin of the single-chip microcomputer U17 is respectively connected to the other ends of the resistors R37, R38, R39 and R41; The first pin of the single-chip microcomputer U16 is respectively connected to one end of the capacitor C10, one end of the capacitor C23, and the positive electrode VCC end of the D / A part; the second pin of the single-chip microcomputer U16 is respectively connected to the other end of the capacitor C10, the other end of the capacitor C23, one end of the capacitor C24, and one end of the capacitor C11, and then connected to the ground; the third pin of the single-chip microcomputer U16 is respectively connected to the other end of the capacitor C24, the other end of the capacitor C11, the eighth pin of the single-chip microcomputer U17, and the other ends of the resistors R37, R38, R39, and R41; The negative electrode of the D / A part is connected to the ground, and the input end of the D / A part is connected to the first-stage amplification module.

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