Impedance box and system for measuring speaker impedance

Abstract

The present application discloses an impedance box and a system for measuring the impedance of a loudspeaker, comprising: a first selection switch, a second selection switch, a first reference resistor and a second reference resistor; the first end and the second end of the first reference resistor are respectively connected to the first moving contact of the first selection switch and the negative port of an amplifier; the first end and the second end of the second reference resistor are respectively connected to the second moving contact of the first selection switch and the negative port of the amplifier; the static contact of the first selection switch is connected to the first test port; the static contact of the first selection switch is connected to the first moving contact of the second selection switch, and the second moving contact of the second selection switch is connected to the positive port of the amplifier; the static contact of the second selection switch is connected to the second test port; the first end of the first reference resistor is connected to the negative interface of the first loudspeaker, and the first end of the second reference resistor is connected to the negative interface of the second loudspeaker, so that the switching time of the reference resistors during the impedance measurement process can be reduced and the efficiency can be improved.

Description

Technical Field

[0001] The present application relates to the field of testing technology, and in particular to an impedance box and a system for measuring the impedance of a loudspeaker. Background Art

[0002] Currently, all electronic products include speakers, such as smart wearables and smart homes. The impedance of the speaker is the main performance parameter of the speaker. Therefore, the impedance curve of the speaker needs to be measured during the design process.

[0003] Many key parameters can be derived from the impedance curve of the speaker. The existing speaker impedance measurement method is the voltage division method, which divides the voltage by connecting a reference resistor in series with the speaker to be tested, calculates the current passing through, and thus converts the impedance curve of the speaker during operation. The common nominal impedance of the speaker is 2Ω-32Ω, and the selection standard of the reference resistor is 1 / 10-1 / 100 of the nominal impedance of the speaker. The reference resistor replacement process is relatively time-consuming.

[0004] Moreover, before using the voltage division method to measure impedance, the measurement system needs to be calibrated, and switching the reference resistor during voltage calibration is also time-consuming. Summary of the invention

[0005] In view of this, the present application provides an impedance box and system for measuring speaker impedance, which can reduce the switching time during the impedance measurement process and improve efficiency.

[0006] The present application provides an impedance box for measuring speaker impedance, comprising: a first selection switch, a second selection switch, a first reference resistor and a second reference resistor;

[0007] A first end and a second end of the first reference resistor are connected to a first moving contact of the first selection switch and a negative port of the amplifier respectively;

[0008] A first end and a second end of the second reference resistor are connected to the second moving contact of the first selection switch and the negative port of the amplifier respectively;

[0009] The static contact of the first selector switch is connected to the first test port;

[0010] The static contact of the first selection switch is connected to the first moving contact of the second selection switch, and the second moving contact of the second selection switch is connected to the positive port of the amplifier;

[0011] The static contact of the second selection switch is connected to the second test port;

[0012] The first end of the first reference resistor is connected to the first speaker negative interface, the first end of the second reference resistor is connected to the second speaker negative interface, and the first speaker positive interface, the second speaker positive interface and the amplifier positive port are connected together.

[0013] Preferably, when the impedance box is used for voltage calibration, the static contact of the first selection switch is connected to the first moving contact or the second moving contact of the first selection switch, and the first test port serves as a speaker terminal voltage calibration interface.

[0014] Preferably, when the impedance box is used for voltage calibration, the static contact of the second selection switch is connected to the second moving contact of the second selection switch, and the second test port serves as an amplifier output voltage calibration interface.

[0015] Preferably, when using the impedance box to measure impedance, the static contact of the second selection switch is connected to the first moving contact of the second selection switch, the static contact of the first selection switch is connected to the first moving contact or the second moving contact of the first selection switch, and the second test port serves as a reference resistance voltage divider acquisition port.

[0016] Preferably, the resistance value of the first reference resistor is 0.1 ohm, and the resistance value of the second reference resistor is 1 ohm.

[0017] The present application also provides a system for measuring speaker impedance, comprising: the impedance box described above, and further comprising: a CPU, a sound card, and an amplifier;

[0018] The CPU is used to set the input voltage of the sound card;

[0019] The output end of the sound card is connected to the input end of the amplifier, and the output end of the amplifier is connected to the negative port of the amplifier and the positive port of the amplifier of the impedance box;

[0020] The first speaker negative interface and the first speaker positive interface of the impedance box are used to connect a speaker or a standard resistor;

[0021] or,

[0022] The second speaker negative interface and the second speaker positive interface of the impedance box are used to connect a speaker or a standard resistor.

[0023] Preferably, the system is used to perform voltage calibration when the impedance box is connected to a standard resistor;

[0024] When the impedance box is connected to the speaker, the system is used to measure the impedance of the speaker.

[0025] Preferably, when the impedance box is connected to the speaker, the CPU is also used to obtain the voltage U parameter of the reference resistor, obtain the loop current I according to the reference resistor and U parameter, and obtain the impedance of the speaker according to the voltage across the speaker and the loop current I, and the reference resistor is the first reference resistor or the second reference resistor.

[0026] Preferably, when the impedance box is connected to the speaker, the CPU is also used to obtain the voltage U parameter of the reference resistor, obtain the loop current I based on the reference resistor and U parameter, and obtain the impedance of the speaker based on the output voltage of the amplifier, U parameter and the loop current I, and the reference resistor is the first reference resistor or the second reference resistor.

[0027] Preferably, the CPU is specifically used to obtain the difference between the output voltage of the amplifier and the U parameter, and divide the difference by the loop current to obtain the impedance of the speaker.

[0028] It can be seen that this application has the following beneficial effects:

[0029] The impedance box for measuring the impedance of a speaker provided by the present application includes two reference resistors. By toggling the gear position of the first selection switch, the switching between the first reference resistor and the second reference resistor can be realized; since the resistance value of the second reference resistor is ten times that of the first reference resistor, the resistance value of the reference resistor is selected according to 1 / 10 to 1 / 100 of the nominal impedance of the speaker to be measured, which can meet the impedance test requirements of most speakers. The impedance box for measuring the impedance of a speaker provided by the present application can replace the reference resistor by changing the switch gear position, so that the impedance curves of different speakers can be measured, which reduces the time of switching the reference resistor during the impedance measurement process, improves efficiency, and is convenient and fast. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A schematic diagram of a system for measuring speaker impedance provided by the present application;

[0031] Figure 2 A schematic diagram of voltage calibration for the system provided by the present application;

[0032] Figure 3 A circuit diagram of an impedance box provided in an embodiment of the present application;

[0033] Figure 4 A switch state diagram of the impedance box provided in an embodiment of the present application;

[0034] Figure 5 Another switching state diagram of the impedance box provided in an embodiment of the present application. DETAILED DESCRIPTION

[0035] The impedance measurement method of the speaker mainly adopts the voltage division method, that is, by connecting a reference resistor in series with the speaker to be tested, collecting the voltage divided on the reference resistor, calculating the current flowing through according to the voltage and the reference resistor, and converting the impedance curve of the speaker during operation according to the current.

[0036] When measuring the impedance curve of a speaker using the voltage divider method, it is necessary to select a suitable reference resistor based on the nominal impedance of the speaker; generally, the reference resistor is 1 / 10 to 1 / 100 of the nominal impedance of the speaker. The nominal impedance of common speakers ranges from 2Ω to 32Ω, so the reference resistor needs to be replaced when measuring different speakers. The replacement process of the reference resistor is relatively time-consuming.

[0037] The impedance box for measuring the speaker impedance provided in the present application includes two reference resistors, and the reference resistors can be switched by toggling the gear position of a selection switch, which makes it more convenient and quick to switch the reference resistors and saves time.

[0038] In order to more clearly understand the various embodiments of the present application, the specific application scenarios of the technical solutions provided by the present application are first introduced below.

[0039] See also Figure 1 , which is a schematic diagram of the system for measuring speaker impedance provided by the present application.

[0040] The system for measuring speaker impedance provided by this embodiment includes: a CPU 100 , a sound card 200 , an amplifier 300 and an impedance box 400 .

[0041] When measuring the speaker impedance, the impedance box 400 of the measurement system is used to connect the speaker to be tested; the CPU 100 can set different voltages as needed, and the voltages are applied to the impedance box 400 after passing through the sound card 200 and the amplifier 300 in sequence. The sound card 200 collects the divided voltage of the reference resistor in the impedance box 400 and returns it to the CPU 100, which calculates and obtains the impedance curve of the speaker to be tested.

[0042] Because the system voltage needs to be calibrated in advance before measuring impedance using the voltage division method, the impedance box provided in the present application can be applied to the above-mentioned system for measuring speaker impedance to perform voltage calibration and impedance measurement.

[0043] See also Figure 2 , which is a schematic diagram of voltage calibration of the system provided in this application.

[0044] In the system for measuring speaker impedance provided in this embodiment, only when voltage calibration is performed, the impedance box 400 is used to connect a standard resistor, the resistance value of which is the resistance value corresponding to the nominal impedance of the speaker to be measured.

[0045] When performing voltage calibration, the following two methods are included: collecting the voltage across the speaker and collecting the output voltage of the amplifier. Both require CPU100 to set the input voltage U1 of the sound card 200, collect the voltage across the speaker or the output voltage U2 of the power amplifier, and obtain the system loop gain coefficient k; thereby ensuring that when measuring the speaker impedance, according to the required voltage U2, CPU100 sets the corresponding input voltage U1=U2 / k.

[0046] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the embodiments of the present application are further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0047] See also Figure 3 , which is a circuit diagram of an impedance box provided in an embodiment of the present application.

[0048] The impedance box for measuring the impedance of a speaker provided in an embodiment of the present application includes: a first selection switch S1, a second selection switch S2, a first reference resistor R1, and a second reference resistor R2. The resistance value of the second reference resistor R2 is ten times the resistance value of the first reference resistor R1. In addition, R1 can also be other multiples of R2, which is not specifically limited here. R2 is about ten times R1 to meet the test requirements of different speakers.

[0049] The present application does not specifically limit the specific resistance values ​​of the first reference resistor R1 and the second reference resistor R2. For example, the resistance value of the first reference resistor may be 0.1Ω, and the resistance value of the second reference resistor may be 1Ω. Because the resistance value of the reference resistor is selected according to 1 / 10 to 1 / 100 of the nominal impedance of the speaker to be measured, the impedance box can measure speakers with a nominal impedance between 1Ω and 100Ω, which is sufficient to cover the nominal impedance range of most common speakers. The resistance value of the first reference resistor R1 and the resistance value of the second reference resistor R2 may also take other values.

[0050] A first end and a second end of the first reference resistor R1 are connected to a first moving contact c of the first selection switch S1 and the amplifier negative port AMP-, respectively.

[0051] A first end and a second end of the second reference resistor R2 are connected to the second moving contact b of the first selection switch S1 and the amplifier negative port AMP-, respectively.

[0052] The stationary contact a of the first selection switch S1 is connected to the first test port A.

[0053] The static contact a of the first selection switch S1 is connected to the first moving contact e of the second selection switch S2, and the second moving contact f of the second selection switch S2 is connected to the positive port AMP+ of the amplifier.

[0054] The static contact d of the second selection switch S2 is connected to the second test port B.

[0055] The first end of the first reference resistor R1 is connected to the first speaker negative interface Z1-, and the first end of the second reference resistor R2 is connected to the second speaker negative interface Z2-; the first speaker positive interface Z1+, the second speaker positive interface Z2+ and the amplifier positive port AMP+ are connected together.

[0056] According to the above connection method, the impedance box provided in the embodiment of the present application can switch the reference resistor by toggling the gear position of the first selection switch S1; when the static contact a of the first selection switch S1 is connected to the first moving contact c of the first selection switch S1, it indicates that the first reference resistor R1 is selected; when the static contact a of the first selection switch S1 is connected to the second moving contact b of the first selection switch S1, it indicates that the second reference resistor R2 is selected.

[0057] When using the first reference resistor R1 for testing, the speaker to be tested should be connected between the first speaker positive interface Z1+ and the first speaker negative interface Z1-; when using the second reference resistor R2 for testing, the speaker to be tested should be connected between the second speaker positive interface Z2+ and the second speaker negative interface Z2-.

[0058] The impedance box for measuring the impedance of a speaker provided by the present application includes two reference resistors. By toggling the gear position of the first selection switch, the switching between the first reference resistor and the second reference resistor can be realized; since the resistance value of the second reference resistor is ten times that of the first reference resistor, the resistance value of the reference resistor is selected according to 1 / 10 to 1 / 100 of the nominal impedance of the speaker to be measured, which can meet the impedance test requirements of most speakers. The impedance box for measuring the impedance of a speaker provided by the present application can replace the reference resistor by changing the switch gear position, so that the impedance curves of different speakers can be measured, which reduces the time of switching the reference resistor during the impedance measurement process, improves efficiency, and is convenient and fast.

[0059] Since the two voltage calibration methods correspond to two different impedance calculation methods, the specific working method of the impedance box provided in the embodiment of the present application when different impedance calculation methods are adopted will be described in detail below with reference to the accompanying drawings.

[0060] The first method: Use the voltage across the speaker to perform voltage calibration and impedance measurement. The following is an example of connecting the first reference resistor.

[0061] See also Figure 4 , which is a switching state diagram of the impedance box provided in an embodiment of the present application.

[0062] The static contact a of the first selection switch S1 is connected to the first moving contact c of the first selection switch S1, indicating that the first reference resistor R1 is selected; the static contact d of the second selection switch S2 is connected to the first moving contact e of the second selection switch S2; the first test port A is used as the speaker end voltage calibration interface; the second test port B is used as the reference resistor voltage division acquisition interface.

[0063] At this time, the first end of the first test port A is connected to the amplifier positive port AMP+, and the amplifier positive port AMP+ is connected to the first speaker positive interface Z1+; the second end of the first test port A is connected to the first speaker negative interface Z1- through the first selection switch S1; therefore, the voltage tested by the first test port is the voltage across the speaker, which is used for voltage calibration.

[0064] The first end of the second test port B is connected to the first end of the first reference resistor R1 through the second selection switch S2 and the first selection switch S1; the second end of the second test port B is connected to the second end of the first reference resistor R1; therefore, the voltage tested by the second test port is the voltage of the reference resistor, which is used to calculate the current for impedance measurement.

[0065] In order to enable those skilled in the art to better understand the impedance box provided in the embodiments of the present application, the principle of impedance measurement is introduced below.

[0066] The voltage across the speaker after calibration is U D ; The divided voltage of the first reference resistor R1 collected through the second test port is U parameter.

[0067] Then the loop current I is:

[0068]

[0069] Speaker impedance R D for:

[0070]

[0071] The second method: Use the voltage collected from the amplifier output to perform voltage calibration and impedance measurement. The following is an example of connecting the first reference resistor.

[0072] See also Figure 5 , this figure is another switching state diagram of the impedance box provided in an embodiment of the present application.

[0073] The static contact a of the first selection switch S1 is connected to the first moving contact c of the first selection switch S1, indicating that the first reference resistor R1 is selected; the static contact d of the second selection switch S2 is connected to the second moving contact f of the second selection switch S2; the second test port B serves as the amplifier output voltage calibration interface.

[0074] At this time, the first end of the second test port B is connected to the amplifier positive port AMP+ through the second selection switch S2; the second end of the second test port B is connected to the amplifier negative port AMP-; therefore, the voltage tested by the second test port is the voltage of the amplifier output end, which is used for voltage calibration.

[0075] After voltage calibration, the static contact d of the second selection switch S2 is connected to the first moving contact e of the second selection switch S2; the second test port B is used as a reference resistor voltage division acquisition interface.

[0076] Continue to see Figure 4 , the first end of the second test port B is connected to the first end of the first reference resistor R1 through the second selection switch S2 and the first selection switch S1; the second end of the second test port B is connected to the second end of the first reference resistor R1; therefore, the voltage tested by the second test port at this time is the voltage of the reference resistor, which is used to calculate the current for impedance measurement.

[0077] In order to enable those skilled in the art to better understand the impedance box provided in the embodiments of the present application, the principle of impedance measurement is introduced below.

[0078] The output voltage of the calibrated amplifier is U A ; The divided voltage of the first reference resistor R1 collected through the second test port is U parameter.

[0079] The calculation formula of the loop current I is the same as formula (1)

[0080] Speaker impedance R D for:

[0081]

[0082] The impedance box for measuring speaker impedance provided in the embodiment of the present application can also collect the voltage at both ends of the speaker or the voltage at the output end of the amplifier through the different gears of the first selection switch and the second selection switch to switch the voltage calibration mode to meet the needs of different calculation methods for measuring speaker impedance, which is more flexible and convenient.

[0083] Based on the impedance box for measuring speaker impedance provided in the above embodiment, the embodiment of the present application further provides a system for measuring speaker impedance, which is described in detail below in conjunction with the accompanying drawings.

[0084] Continue to see Figure 1 and Figure 2 The system for measuring speaker impedance provided in the embodiment of the present application includes: a CPU 100, a sound card 200, an amplifier 300 and an impedance box 400 provided in the above embodiment.

[0085] The CPU 100 is used to set the input voltage of the sound card 200 .

[0086] The output end of the sound card 200 is connected to the input end of the amplifier 300 , and the output end of the amplifier 300 is connected to the amplifier negative port and the amplifier positive port of the impedance box 400 .

[0087] The first speaker negative interface and the first speaker positive interface of the impedance box 400 are used to connect a speaker or a standard resistor;

[0088] or,

[0089] The second speaker negative interface and the second speaker positive interface of the impedance box 400 are used to connect a speaker or a standard resistor.

[0090] When the impedance box 400 is connected to a standard resistor, the system provided by the embodiment of the present application can perform voltage calibration; wherein the resistance value of the standard resistor is the resistance value corresponding to the nominal impedance of the speaker to be measured.

[0091] When the impedance box 400 is connected to a speaker, the system provided by the embodiment of the present application can measure the impedance of the speaker.

[0092] When testing with the first reference resistor, the speaker should be connected between the first speaker positive interface and the first speaker negative interface; when testing with the second reference resistor, the speaker should be connected between the second speaker positive interface and the second speaker negative interface.

[0093] When the impedance box 400 is connected to the speaker, the CPU 100 is also used to obtain the voltage U parameter of the reference resistor, obtain the loop current I according to the resistance value of the reference resistor and the voltage U parameter of the reference resistor, and obtain the loop current I according to the voltage U across the speaker. D The impedance of the speaker is obtained by using the loop current I; wherein the reference resistor is the first reference resistor or the second reference resistor in the impedance box.

[0094] When the impedance box 400 is connected to the speaker, the CPU 100 can also be used to obtain the voltage U parameter of the reference resistor, obtain the loop current I according to the resistance value of the reference resistor and the voltage U parameter of the reference resistor, and obtain the loop current I according to the output voltage U of the amplifier 300. A , the voltage U of the reference resistor and the loop current I are used to obtain the impedance of the speaker; wherein the reference resistor is the first reference resistor or the second reference resistor in the impedance box; wherein the CPU 100 is specifically used to obtain the output voltage U of the amplifier 300 A The difference between the voltage U across the reference resistor and the impedance of the speaker is obtained by dividing the difference by the loop current.

[0095] The system for measuring speaker impedance provided by the embodiment of the present application adopts an impedance box for measurement. The impedance box includes two reference resistors. By switching the switch position of the impedance box, the reference resistors connected can be switched to measure the impedance of different speakers. The system for measuring speaker impedance provided by the present application can measure the impedance curves of different speakers by changing the switch position to achieve the replacement of the reference resistors, thereby reducing the time for switching the reference resistors during the impedance measurement process, improving efficiency, and being convenient and quick. In addition, the system provided by the embodiment of the present application can also select the voltage calibration method by switching the switch position of the impedance box, which is more flexible, reduces the time for switching the voltage calibration method, and further improves efficiency.

[0096] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An impedance box for measuring speaker impedance, characterized in that: include: a first selection switch, a second selection switch, a first reference resistor, and a second reference resistor; The resistance value of the first reference resistor and the resistance value of the second reference resistor are selected according to 1 / 10 to 1 / 100 of the nominal impedance of the speaker to be tested; the resistance value of the second reference resistor is several times the resistance value of the first reference resistor; The first end and the second end of the first reference resistor are connected to the first moving contact of the first selection switch and the negative port of the amplifier respectively; The first end and the second end of the second reference resistor are connected to the second moving contact of the first selection switch and the negative port of the amplifier respectively; The static contact of the first selection switch is connected to the second end of the first test port; the first end of the first test port is connected to the positive port of the amplifier; The static contact of the first selection switch is connected to the first moving contact of the second selection switch, and the second moving contact of the second selection switch is connected to the positive port of the amplifier; The static contact of the second selection switch is connected to the first end of the second test port; The second end of the second test port is connected to the negative port of the amplifier; The first end of the first reference resistor is connected to the negative interface of the first speaker, the first end of the second reference resistor is connected to the negative interface of the second speaker, and the positive interface of the first speaker, the positive interface of the second speaker and the positive port of the amplifier are connected together; when the first reference resistor is used for testing, the speaker to be tested should be connected between the positive interface of the first speaker and the negative interface of the first speaker; when the second reference resistor is used for testing, the speaker to be tested should be connected between the positive interface of the second speaker and the negative interface of the second speaker.

2. The impedance box according to claim 1, characterized in that: When the impedance box is used for voltage calibration, the static contact of the first selection switch is connected to the first moving contact or the second moving contact of the first selection switch, and the first test port serves as a speaker terminal voltage calibration interface.

3. The impedance box according to claim 1, characterized in that: When the impedance box is used for voltage calibration, the static contact of the second selection switch is connected to the second moving contact of the second selection switch, and the second test port serves as an amplifier output voltage calibration interface.

4. The impedance box according to claim 1, characterized in that: When the impedance box is used to perform impedance measurement, the static contact of the second selection switch is connected to the first moving contact of the second selection switch, the static contact of the first selection switch is connected to the first moving contact or the second moving contact of the first selection switch, and the second test port is used as a reference resistance voltage division acquisition port.

5. The impedance box according to any one of claims 1 to 3, characterized in that: The resistance value of the first reference resistor is 0.1 ohm, and the resistance value of the second reference resistor is 1 ohm.

6. A system for measuring speaker impedance, characterized in that: include: The impedance box according to any one of claims 1 to 5, further comprising: a CPU, a sound card and an amplifier; The CPU is used to set the input voltage of the sound card; The output end of the sound card is connected to the input end of the amplifier, and the output end of the amplifier is connected to the amplifier negative port and the amplifier positive port of the impedance box; The first speaker negative interface and the first speaker positive interface of the impedance box are used to connect a speaker or a standard resistor; or, The second speaker negative interface and the second speaker positive interface of the impedance box are used to connect a speaker or a standard resistor.

7. The system according to claim 6, characterized in that When the impedance box is connected to the standard resistor, the system is used to perform voltage calibration; When the impedance box is connected to the speaker, the system is used to measure the impedance of the speaker.

8. The system according to claim 7, characterized in that When the impedance box is connected to the speaker, the CPU is also used to obtain the voltage U parameter of the reference resistor, obtain the loop current I according to the reference resistor and the U parameter, and obtain the impedance of the speaker according to the voltage across the speaker and the loop current I, and the reference resistor is the first reference resistor or the second reference resistor.

9. The system according to claim 7, characterized in that When the impedance box is connected to the speaker, the CPU is also used to obtain the voltage U parameter of the reference resistor, obtain the loop current I according to the reference resistor and the U parameter, and obtain the impedance of the speaker according to the output voltage of the amplifier, the U parameter and the loop current I, and the reference resistor is the first reference resistor or the second reference resistor.

10. The system according to claim 9, characterized in that The CPU is specifically used to obtain the difference between the output terminal voltage of the amplifier and the U parameter, and divide the difference by the loop current to obtain the impedance of the speaker.

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