CN107422192B - Audio equipment input impedance measuring method and device and measurement and verification method and device - Google Patents

Audio equipment input impedance measuring method and device and measurement and verification method and device Download PDF

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CN107422192B
CN107422192B CN201710651658.2A CN201710651658A CN107422192B CN 107422192 B CN107422192 B CN 107422192B CN 201710651658 A CN201710651658 A CN 201710651658A CN 107422192 B CN107422192 B CN 107422192B
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audio
output voltage
tested
audio equipment
input impedance
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CN107422192A (en
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黄瑞哲
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GUANGZHOU RUIFENG AUDIO TECHNOLOGY Corp Ltd
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GUANGZHOU RUIFENG AUDIO TECHNOLOGY Corp Ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
    • G01R27/28—Measuring attenuation, gain, phase shift or derived characteristics of electric four pole networks, i.e. two-port networks; Measuring transient response
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R35/00—Testing or calibrating of apparatus covered by the other groups of this subclass
    • G01R35/005—Calibrating; Standards or reference devices, e.g. voltage or resistance standards, "golden" references

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Abstract

The invention relates to a method and a device for measuring input impedance of audio equipment, and a method and a device for measuring and checking, wherein the measuring device comprises an audio signal generator, a first alternating current millivoltmeter and a variable resistance box; the signal output end of the audio signal generator is connected with the signal input end of the audio equipment to be tested with unbalanced input impedance in series through the variable resistance box, the ground input end of the audio equipment to be tested is connected with the ground output end of the audio signal generator, and the first alternating-current millivoltmeter is connected with the rated load of the output end of the audio equipment to be tested in parallel. The method and the device can directly read the required data and have the advantages of high efficiency, simple operation method and difficult error in the process.

Description

Audio equipment input impedance measuring method and device and measurement and verification method and device
Technical Field
The invention relates to the technical field of impedance measurement, in particular to a method and a device for measuring input impedance of audio equipment and a method and a device for measuring and checking the input impedance of the audio equipment.
Background
Input impedance, i.e., the internal impedance measured between the input terminals of an audio device, is an important product indicator for audio devices. In a built-up system, audio equipment is connected with each other, and the influence of input impedance is important for signal transmission.
A relatively simple method for audio device input impedance has long been the use of a comparison method. The audio equipment to be measured is firstly under the standard measurement condition, the voltage U1 at the input end of the audio equipment is measured by using the alternating current millivoltmeter, then the variable resistor is switched to a verified variable resistor, the variable resistor is adjusted to ensure that the reading of the alternating current millivoltmeter is still U1, then the resistance value of the variable resistor is separately measured, and the resistance value of the variable resistor is equal to the modulus of the input impedance of the audio equipment at the measurement frequency.
However, in this measurement method, the reactance component of the input impedance of the ac millivoltmeter may affect the measurement result, i.e. the shunting effect of the input impedance of the ac millivoltmeter on the input signal current is the main cause of the measurement error.
Disclosure of Invention
Based on the method, the device and the method for measuring and verifying the input impedance of the audio equipment are provided.
An audio device input impedance measurement apparatus comprising:
the audio signal generator, the first alternating current millivoltmeter and the variable resistance box;
the signal output end of the audio signal generator is connected to the unbalanced signal input end of the audio equipment to be tested through the variable resistance box, the ground input end of the audio equipment to be tested is connected with the ground output end of the audio signal generator, the first alternating-current millivoltmeter is connected with the output end of the audio equipment to be tested, and the output end of the audio equipment is connected with a rated load;
the first alternating-current millivoltmeter is used for measuring the output voltage of the audio equipment to be tested, wherein the first output voltage of the audio equipment to be tested is obtained by setting the resistance value of the variable resistance box to zero; the resistance value of the variable resistance box is adjusted to obtain a second output voltage of the audio equipment to be tested; and when the second output voltage is half of the first output voltage, the mode of the input impedance of the audio equipment to be tested is the corresponding resistance value of the variable resistance box.
An audio device input impedance measurement method, comprising the steps of:
setting the resistance value of the variable resistance box to zero, and adjusting the output voltage of the signal generator to enable the tested audio equipment to be placed under the standard measurement condition;
finding out a middle frequency point of a frequency response straight section under the standard measuring condition, taking the frequency point as a frequency point for measuring the input impedance of the audio equipment, and reading a first output voltage of a first alternating-current millivoltmeter;
adjusting the resistance value of the variable resistance box to increase the resistance value of the variable resistance box, and reading a second output voltage of the first alternating-current millivoltmeter;
and when the second output voltage is half of the first output voltage and the test frequency point is still in a straight section of frequency response, taking the current resistance value of the variable resistance box as a mode of the input impedance of the audio equipment to be tested.
According to the device and the method for measuring the input impedance of the audio equipment, the first output voltage of the audio equipment to be measured is measured when the resistance value of the variable resistance box is zero through the first alternating-current millivoltmeter; the resistance value of the variable resistance box is adjusted to obtain a second output voltage of the audio equipment to be tested; when the audio equipment to be tested works in the frequency response straight section, according to the principle that the gain of a linear interval is constant, the output voltage is halved when the input voltage is halved, and conversely, the input voltage is halved when the output voltage is halved. When the resistance value of the variable resistance box is equal to the modulus of the input impedance of the audio equipment to be measured, the reading of the first alternating current millivoltmeter is halved, so that the modulus of the input impedance of the audio equipment to be measured can be directly read out through the variable resistance box, the measurement process fully utilizes the principle that the gain of the audio equipment working in a linear region is unchanged, the measurement of the input impedance is realized, data can be directly read from the variable resistance box, and the method has the advantages of high efficiency, simple operation method and difficulty in making mistakes in the process.
An audio device input impedance measurement apparatus comprising:
the audio signal generator, the first alternating current millivoltmeter and the duplex variable resistance box;
the audio signal generator comprises an audio signal generator, a duplex variable resistance box, a double-input end, a double-output end, a first output end, a second output end and a third output end, wherein the signal output end of the audio signal generator is connected with the first input end of the duplex variable resistance box;
the first alternating-current millivoltmeter is used for measuring the output voltage of the audio equipment to be tested, wherein the first output voltage of the audio equipment to be tested is obtained by setting the resistance value of the duplex variable resistance box to zero; the resistance value of the duplex variable resistance box is adjusted to obtain a second output voltage of the audio equipment to be tested; and when the second output voltage is half of the first output voltage, the sum of the current resistance values of the two resistors of the duplex variable resistance box is used as the mode of the input impedance of the audio equipment to be tested.
An audio device input impedance measurement method, comprising the steps of:
setting the resistance values of two resistors of the duplex variable resistance box to zero, and adjusting the output voltage of the signal generator to enable the tested audio equipment to be placed under the standard measurement condition;
finding out a midpoint frequency point of a frequency response straight section under the standard measurement condition, taking the frequency point as a test frequency point for measuring the input impedance of the audio equipment, and reading a first output voltage of a first alternating-current millivoltmeter;
synchronously adjusting the resistance values of two resistors of the duplex variable resistance box to increase the resistance value of the duplex variable resistance box, and reading a second output voltage of the first alternating-current millivoltmeter;
and when the second output voltage is half of the first output voltage and the test frequency point is still within the straight section of the frequency response, taking the sum of the current resistance values of the two resistors of the duplex variable resistance box as the mode of the input impedance of the audio equipment to be tested.
According to the device and the method for measuring the input impedance of the audio equipment, the first output voltage of the audio equipment to be measured is measured when the resistance value of the duplex variable resistance box is zero through the first alternating-current millivoltmeter; the resistance value of the duplex variable resistance box is adjusted to obtain a second output voltage of the audio equipment to be tested; when the audio equipment to be tested works in the frequency response straight section, according to the principle that the gain of a linear interval is constant, the output voltage is halved when the input voltage is halved, and conversely, the input voltage is halved when the output voltage is halved. When the sum of the resistance values of the duplex variable resistance box is equal to the modulus of the input impedance of the audio equipment to be tested, the reading of the first alternating current millivoltmeter is halved, so that the modulus of the input impedance of the audio equipment to be tested can be directly read through the duplex variable resistance box, the input impedance measurement is realized by fully utilizing the principle that the gain of the audio equipment in a linear region is unchanged in the measurement process, the data can be directly read, and the method has the advantages of high efficiency, simple operation method and difficulty in error in the process.
An audio device input impedance measurement verification apparatus, comprising:
the audio signal generator, the first alternating current millivoltmeter, the resistor and the switching device;
the signal output end of the audio signal generator is connected with the unbalanced signal input end of the audio equipment to be tested through the resistor, the ground input end of the audio equipment to be tested is connected with the ground output end of the audio signal generator, the output end of the audio equipment is connected with a rated load, the first alternating current millivoltmeter is connected with the rated load of the output end of the audio equipment to be tested in parallel, and the switching device is bridged at two ends of the resistor; the resistance value of the resistor is equal to the measured modulus of the input impedance of the audio equipment to be tested, and the resistance value of the resistor is also equal to the nominal value of the audio equipment to be tested;
the first alternating-current millivoltmeter measures the output voltage of the audio equipment to be tested, wherein the first output voltage of the audio equipment to be tested when the switching device is closed is included; and a second output voltage of the audio equipment to be tested when the switching device is switched off; if the second output voltage is equal to one half of the first output voltage, the resistance value of the resistor is equal to the modulus of the input impedance of the audio equipment to be tested.
An audio device input impedance measurement verification method comprises the following steps:
closing the switch device, and adjusting the output voltage of the signal generator to enable the tested audio equipment to be placed under the standard measurement condition;
finding out a middle frequency point of the frequency response straight section under the standard measurement condition, taking the frequency point as a frequency point for measuring the input impedance of the audio equipment, and measuring a first output voltage of the audio equipment to be measured through a first alternating current millivoltmeter;
disconnecting the switching device, and measuring a second output voltage of the audio equipment to be measured through a first alternating-current millivoltmeter;
and if the second output voltage is equal to one half of the first output voltage and the test frequency point is still in a straight section of frequency response, judging that the modulus of the input impedance of the audio equipment to be tested is equal to the resistance value of the resistor. And a second output voltage of the audio equipment to be tested when the switching device is switched off; if the second output voltage is equal to one half of the first output voltage, the resistance value of the resistor is equal to the modulus of the input impedance of the audio equipment to be tested.
According to the measurement and calibration device and the measurement and calibration method for the input impedance of the audio equipment, the first output voltage of the audio equipment to be tested is measured when the switch device is closed through the first alternating-current millivoltmeter; and a second output voltage of the audio equipment to be tested when the switching device is switched off; when the audio equipment to be tested works in a frequency response straight section, according to the principle that the gain of a linear interval is constant, the output voltage is halved when the input voltage is halved, otherwise, the input voltage is halved when the output voltage is halved, and if the second output voltage is equal to one half of the first output voltage, the resistance value of the resistor is equal to the modulus of the input impedance of the audio equipment to be tested. The principle that the gain of the audio equipment in a linear region is unchanged is fully utilized in the measurement and calibration process, the online measurement and calibration of the input impedance are realized, and the method has the advantages of high efficiency, simple operation method and difficulty in making mistakes in the process.
An audio device input impedance measurement verification apparatus, comprising:
the audio signal generator, the first alternating current millivoltmeter, the first resistor, the second resistor, the first switching device and the second switching device;
the positive output end of the balanced output of the audio signal generator is connected with the first input end of the first resistor, the negative output end of the balanced output of the audio signal generator is connected with the second input end of the second resistor, the first output end of the first resistor is connected with the positive end of the balanced input end of the audio equipment to be tested, and the second output end of the second resistor is connected with the negative end of the balanced input end of the audio equipment to be tested; the output end of the audio equipment is connected with a rated load; the first alternating-current millivoltmeter is connected with a rated load of the output end of the audio equipment to be tested in parallel, the first switching device is connected with the first resistor in parallel, and the second switching device is connected with the second resistor in parallel; the sum of the resistance values of the first resistor and the second resistor is equal to the modulus of the measured input impedance of the audio equipment to be tested, and the resistance value of the first resistor is equal to the resistance value of the second resistor; the resistance value of the resistor is also equal to the nominal value of the audio equipment to be tested;
the first alternating-current millivoltmeter measures the output voltage of the audio equipment to be tested, wherein the first output voltage of the audio equipment to be tested when the first switch device and the second switch device are both closed is included; and a second output voltage of the audio equipment to be tested when the first switching device and the second switching device are both switched off; if the second output voltage is equal to one half of the first output voltage, the modulus of the input impedance of the audio equipment to be tested is equal to the sum of the current resistance values of the first resistor and the second resistor.
An audio device input impedance measurement verification method comprises the following steps:
closing the first switch device and the second switch device at the same time, and adjusting the output voltage of the signal generator to enable the tested audio equipment to be placed under the standard measurement condition;
finding out a midpoint frequency point of the frequency response straight section under the standard measurement condition, taking the frequency point as a frequency point for measuring the input impedance of the audio equipment, and measuring a first output voltage of the audio equipment to be measured through a first alternating current millivoltmeter;
simultaneously disconnecting the first switching device and the second switching device, and measuring a second output voltage of the audio equipment to be tested through a first alternating current millivoltmeter;
and if the second output voltage is equal to one half of the first output voltage and the test frequency point is still in a straight section of frequency response, judging that the modulus of the input impedance of the audio equipment to be tested is equal to the sum of the current resistance values of the first resistor and the second resistor.
According to the device and the method for measuring and checking the input impedance of the audio equipment, the first output voltage of the audio equipment to be tested is measured when the first switch device and the second switch device are both closed through the first alternating-current millivoltmeter; and a second output voltage of the audio equipment to be tested when the first switching device and the second switching device are both switched off; when the audio equipment to be tested works in the frequency response straight section, according to the principle that the gain of a linear section is constant, the output voltage is also halved when the input voltage is halved, otherwise, the input voltage is halved when the output voltage is halved, if the second output voltage is equal to one half of the first output voltage and the testing frequency point is still in the frequency response straight section, the modulus of the measured input impedance of the audio equipment to be tested is equal to the nominal value of the input impedance of the audio equipment to be tested, the measurement and verification process fully utilizes the principle that the gain of the audio equipment working in the linear section is unchanged, the online measurement and verification of the input impedance are realized, and the audio equipment to be tested has the advantages of high efficiency, simple operation method and difficulty in error generation in the process.
Drawings
Fig. 1 is a schematic structural diagram of an input impedance measuring apparatus of an audio device according to a first embodiment of the present invention;
FIG. 2 is a flowchart of an input impedance measuring method of an audio device according to a first embodiment of the present invention;
FIG. 3 is a schematic structural diagram of an input impedance measurement and verification apparatus for an audio device according to a first embodiment of the present invention;
FIG. 4 is a flowchart of a method for calibrating input impedance measurement of an audio device according to a first embodiment of the present invention;
FIG. 5 is a schematic structural diagram of an input impedance measuring apparatus of an audio device according to a second embodiment of the present invention;
FIG. 6 is a schematic structural diagram of an input impedance measurement and verification apparatus for an audio device according to a second embodiment of the present invention;
FIG. 7 is a flowchart of an input impedance measuring method of an audio device according to a second embodiment of the present invention;
fig. 8 is a flowchart of an audio device input impedance measurement verification method according to a second embodiment of the present invention.
Detailed Description
The technical solution of the present invention will be explained below with reference to the accompanying drawings.
Example one
As shown in fig. 1, an embodiment of the present invention provides an audio device input impedance measuring apparatus, which may include:
the audio signal generator S, the first alternating current millivoltmeter U1 and the variable resistance box R;
the signal output end of the audio signal generator S is connected to the unbalanced signal input end of the audio equipment to be tested through the variable resistance box R, the ground input end of the audio equipment to be tested is connected with the ground output end of the audio signal generator S, and the output end of the audio equipment is connected with the rated load RL(ii) a The first alternating-current millivoltmeter U1 and the rated load R of the output end of the audio equipment to be testedLParallel connection;
the first alternating-current millivoltmeter U1 is used for measuring the output voltage of the audio device to be tested, wherein the first output voltage of the audio device to be tested is obtained by setting the resistance value of the variable resistance box R to zero; the resistance value of the variable resistance box R is adjusted to obtain a second output voltage of the audio equipment to be tested; and when the second output voltage is half of the first output voltage and the test frequency point is still in the straight section of the frequency response, the mode of the input impedance of the audio equipment to be tested is the resistance value of the variable resistance box R corresponding to the second output voltage.
The audio device of the present embodiment employs an unbalanced input. When the input impedance of the audio device is unknown, the input impedance measuring device of the audio device can be used for measuring the input impedance of the audio device.
In one embodiment, the audio signal generator S may be an existing product, and to improve the measurement accuracy, the output impedance of the audio signal generator should be much smaller than the input impedance of the audio device, so that its influence should be negligible. In the actual measurement process, the selected output impedance R of the audio signal generator SSThe smaller the better. In the embodiment shown in fig. 1, the variable resistor box R may be a rotary ac-dc resistor box. Preferably, the input impedance of the first ac millivolt meter U1 is selected to be much larger than the output impedance of the audio device, so that the measurement accuracy can be improved.
During measurement, when the resistance value of the variable resistance box R is measured to be zero through the first alternating current millivoltmeter U1, the first output voltage of the audio equipment to be measured is recorded as U1a, and then the resistance value of the variable resistance box R is measured through the first alternating current millivoltmeter U1 and is adjustedAnd marking the second output voltage of the audio equipment to be tested as U1b, and when the value of U1b is reduced to U1a/2, the resistance value of the variable resistor box R and the input impedance R of the audio equipment to be tested at the momentiThe module values are equal, and the corresponding resistance value can be directly read from the variable resistance box R.
To further ensure the accuracy of the measurement process, the audio device under test should be placed under standard measurement conditions, the frequency point at which the first voltage U1a is measured should be the middle frequency point of the frequency response flat segment (e.g., 1kHz, but not limited to 1kHz), and the second voltage U1b is measured, so as to ensure that the frequency point is still within the frequency response flat segment. The frequency point when the first voltage U1a is measured should coincide with the frequency point when the second voltage U1b is measured.
Further, the input impedance measuring device of the audio device of the present invention may further comprise a second alternating current millivoltmeter U2 connected across the signal output terminal of the audio signal generator S and the ground output terminal of the audio signal generator S. The output voltage of the audio signal generator S may be measured by a second millivoltmeter U2, which includes a first input voltage U2a when the resistance of the variable resistor box R is set to zero, and a second input voltage U2b after the resistance of the variable resistor box R is adjusted. Throughout the measurement process, as long as the audio signal generator S outputs the impedance RSSufficiently small, the input voltages U2a and U2b should be unchanged.
It should be noted that the terms "equal", "no change", and the like in the above measurement process include not only the case where the numerical values are completely the same, but also the case where the numerical values are within an acceptable error range. For example, when U1b is said to be equal to U1a/2, it can mean that the value of U1b is identical to the value of U1a/2, or that the value of U1b and the value of U1a/2 are within an acceptable error range.
Preferably, the input impedance of the second ac millivolt meter U2 should be much greater than the output impedance of the audio signal generator.
The audio equipment input impedance measuring device can directly read out the mode of the input impedance of the audio equipment to be measured through the variable resistance box R, the measuring process of the audio equipment input impedance measuring device makes full use of the principle that the audio equipment works in a linear region, data can be directly read, and the audio equipment input impedance measuring device has the advantages of being high in efficiency, simple in operation method and not prone to making mistakes in the process.
Example two
As shown in fig. 2, the present invention further provides an audio device input impedance measuring method, which may include the following steps:
s11, setting the resistance value of the variable resistance box to zero, adjusting the output voltage of the signal generator, and enabling the audio equipment to be tested to be under the standard measurement condition;
s12, finding out the middle frequency point of the frequency response straight section under the standard measuring condition, taking the frequency point as the frequency point for measuring the input impedance of the audio equipment, and reading the first output voltage of the first alternating current millivoltmeter;
s13, adjusting the resistance value of the variable resistance box to increase the resistance value of the variable resistance box, and reading a second output voltage of the first alternating current millivoltmeter;
and S14, when the second output voltage is half of the first output voltage and the test frequency point is still in the straight section of the frequency response, taking the current resistance value of the variable resistance box as the mode of the input impedance of the audio equipment to be tested.
The audio device input impedance measuring method can be implemented based on the audio device input impedance measuring apparatus according to the first embodiment, and embodiments of each element for implementing the audio device input impedance measuring method are not described herein again. The connection mode is as shown in fig. 1, and the audio device of the present embodiment employs an unbalanced input. The input impedance of the audio equipment is unknown, and the input impedance of the audio equipment can be measured by adopting the audio equipment input impedance measuring device. The output end of the audio equipment is connected with a rated load, and the first alternating current millivoltmeter is connected in parallel at two ends of the rated load so as to measure the output voltage of the tested audio equipment.
After the resistance value of the variable resistance box R is set to zero, the output voltage of the signal generator can be adjusted, the audio equipment to be tested is placed under the standard measurement condition, specifically, the frequency of the signal generator can be adjusted to change from 20Hz to 20kHz, the middle frequency point (for example, 1kHz, but not limited to 1kHz) of the frequency response straight section is found out by reading the measurement voltage of the first alternating current millivoltmeter, the frequency point is taken as the frequency point for measuring the input impedance of the audio equipment, and the output voltage of the audio equipment to be tested under the standard measurement condition is read and recorded as the first output voltage. Then, the resistance value of the variable resistance box can be adjusted to increase the resistance value, and the second output voltage of the audio equipment to be tested is measured by reading and recording the first alternating current millivoltmeter until the output voltage of the audio equipment to be tested is half of the first output voltage, and the record is read. The resistance value of the variable resistance box is kept, the frequency of the signal generator is adjusted to change from 20Hz to 20kHz, and at the moment, the frequency point for measuring the input impedance of the audio equipment is in the straight section of the frequency response. And when the second output voltage is half of the first output voltage, reading the current resistance value of the variable resistance box, and taking the current resistance value as the mode of the input impedance of the audio equipment to be tested.
According to the device and the method for measuring the input impedance of the audio equipment, the first output voltage of the audio equipment to be measured is measured when the resistance value of the variable resistance box is zero through the first alternating-current millivoltmeter; the resistance value of the variable resistance box is adjusted to obtain a second output voltage of the audio equipment to be tested; when the audio equipment to be measured works in a frequency response straight section, according to the principle that the gain of a linear section is constant, the output voltage is halved when the input voltage is halved, otherwise, the input voltage is halved when the output voltage is halved, and when the resistance value of the variable resistance box is equal to the mode of the input impedance of the audio equipment to be measured, the reading of the first alternating-current millivoltmeter is halved, so that the mode of the input impedance of the audio equipment to be measured can be directly read out through the variable resistance box.
EXAMPLE III
As shown in fig. 3, the present invention further provides an audio device input impedance measurement verification apparatus, which may include: the audio signal generator S, a first alternating current millivoltmeter U1, a resistor R and a switching device K;
the signal output end of the audio signal generator S is connected to the unbalanced signal input end of the audio equipment to be tested through the resistor R, the ground input end of the audio equipment to be tested is connected with the ground output end of the audio signal generator S, and the output end of the audio equipment is connected with the rated load RLThe first alternating-current millivoltmeter U1 and the rated load R of the output end of the audio equipment to be testedLThe switching device K is connected in parallel and is in bridge connection with two ends of the resistor R; the resistance value of the resistor R is equal to the modulus of the measured input impedance of the audio equipment to be tested;
the first alternating-current millivoltmeter U1 measures the output voltage of the audio equipment to be tested, wherein the first output voltage of the audio equipment to be tested comprises the first output voltage of the audio equipment to be tested when the switch device K is closed; and a second output voltage of the audio equipment to be tested when the switching device K is switched off; if the second output voltage is equal to one half of the first output voltage, the measured modulus of the input impedance of the audio equipment to be tested is equal to the nominal value of the input impedance of the audio equipment to be tested.
By the audio device input impedance measurement and verification device, measurement and verification can be performed on the audio device input impedance measurement device of the first embodiment or the audio device input impedance measurement method of the second embodiment, so that the accuracy of the measurement result can be verified.
In addition, if the input impedance of the audio device product is to be used as a measure for verifying the quality of the product, the measurement of the input impedance of the audio device in the production line is too time-consuming to perform. Since the input impedance of an audio device on a production line is generally a known impedance that has been measured, the measured value of the input impedance can be directly measured on-line. The principle that when the audio equipment works, the gain is constant in the linear working area is also utilized. To audio equipment input impedance R on production lineiThis index is known only for the input impedance R of audio equipment produced on a production lineiOn-line measurements are made to find out whether the values are within the range of the product requirements.
The embodiment can perform measurement verification and online measurement of the input impedance for the audio equipment with unbalanced input, wherein the input impedance is known.
In this embodiment, the audio signal generator S may be an off-the-shelf product. To improve the accuracy of the measurement, the output impedance of the audio signal generator should be much smaller than the input impedance of the audio device, so that its influence should be negligible. In the actual measurement process, the selected output impedance R of the audio signal generator SSThe smaller the better. In the embodiment shown in fig. 1, the variable resistor box R may be a rotary ac-dc resistor box. Preferably, the input impedance of the first ac millivolt meter U1 is selected to be much larger than the output impedance of the audio device, so that the measurement accuracy can be improved.
During verification, the first output voltage of the audio equipment to be tested when the switching device is closed can be measured through the first alternating current millivoltmeter U1 and recorded as U1a, and then the second output voltage of the audio equipment to be tested when the switching device is disconnected is measured through the first alternating current millivoltmeter U1 and recorded as U1 b. If U1b equals U1a/2, then the measured input impedance R of the audio device may be considered to beiAnd the input impedance R of the audio deviceiAre the same. Wherein, the value of the resistance R is equal to the measured input impedance R of the audio equipmentiAre equal in modulus.
In order to further ensure the accuracy of the measurement and verification process, the audio device to be measured should be placed under standard measurement conditions, the frequency point for measuring the first voltage U1a should be the middle frequency point of the frequency response flat section (for example, 1kHz, but not limited to 1kHz), and when measuring the second voltage U1b, it should be ensured that the frequency point is still within the frequency response flat section. The frequency point when the first voltage U1a is measured should coincide with the frequency point when the second voltage U1b is measured.
Further, the input impedance measuring device of the audio device of the present invention may further comprise a second alternating current millivoltmeter U2 connected across the signal output terminal of the audio signal generator S and the ground output terminal of the audio signal generator S. The output voltage of the audio signal generator S may be measured by a second millivoltmeter U2, which includes the zeroth time when the resistance of the variable resistance box R is set to zeroAn input voltage U2a, and a second input voltage U2b with the adjusted resistance of the variable resistor box R. Throughout the measurement process, as long as the audio signal generator S outputs the impedance RSSufficiently small, the input voltages U2a and U2b should be unchanged.
It should be noted that the terms "equal", "no change", and the like in the above measurement process include not only the case where the numerical values are completely the same, but also the case where the numerical values are within an acceptable error range. For example, when U1b is said to be equal to U1a/2, it can mean that the value of U1b is identical to the value of U1a/2, or that the value of U1b and the value of U1a/2 are within an acceptable error range.
Preferably, the input impedance of the second ac millivolt meter U2 should be much greater than the output impedance of the audio signal generator.
In this embodiment, the switching device may be a relay to facilitate automated measurements.
The measurement and calibration device for the input impedance of the audio equipment measures the first output voltage of the audio equipment to be tested when the switch device is closed through the first alternating-current millivoltmeter; when the audio equipment to be tested works in the frequency response straight section, according to the principle that the gain of a linear section is constant, the output voltage is also halved when the input voltage is halved, otherwise, the input voltage is halved when the output voltage is halved, if the second output voltage is equal to one half of the first output voltage and the testing frequency point is still in the frequency response straight section, the modulus of the measured input impedance of the audio equipment to be tested is equal to the nominal value of the input impedance of the audio equipment to be tested, the measurement and verification process fully utilizes the principle that the gain of the audio equipment working in the linear section is unchanged, the online measurement and verification of the input impedance are realized, the data can be directly read, and the method has the advantages of high efficiency, simple operation method and difficulty in error making.
Example four
As shown in fig. 4, the present invention further provides a method for calibrating input impedance measurement of an audio device, which may include the following steps:
s21, closing the switch device, adjusting the output voltage of the signal generator, and making the audio equipment to be measured under the standard measuring condition;
s22, finding out the middle frequency point of the frequency response straight section under the standard measuring condition, taking the frequency point as the frequency point for measuring the input impedance of the audio equipment, and measuring the first output voltage of the audio equipment to be measured through a first alternating current millivoltmeter;
s23, disconnecting the switch device and measuring a second output voltage of the audio equipment to be measured through the first alternating current millivoltmeter;
s24, if the second output voltage is equal to one-half of the first output voltage, determining that the modulus of the measured input impedance of the audio device under test is equal to the nominal value of the input impedance of the audio device under test.
The audio device input impedance measurement and verification method may be implemented based on the audio device input impedance measurement apparatus according to the third embodiment, and embodiments of each element that performs the audio device input impedance measurement and verification method are not described herein again. Connected as shown in fig. 3, the audio device employs an unbalanced input. The output end of the audio equipment is connected with a rated load, and the first alternating current millivoltmeter is connected in parallel at two ends of the rated load so as to measure the output voltage of the tested audio equipment.
In one embodiment, the output voltage of the signal generator may be adjusted to place the audio device under test in standard measurement conditions. Specifically, the frequency of the signal generator may be adjusted to vary from 20Hz to 20kHz, an intermediate frequency point (for example, 1kHz, but not limited to 1kHz) of the frequency response straight segment is found by reading the measurement voltage of the first ac millivoltmeter, the intermediate frequency point is used as a frequency point for measuring the input impedance of the audio device, and the output voltage of the audio device to be measured under the standard measurement condition is read and recorded as the first output voltage. The switch may then be opened and the recorded first ac millivoltmeter may be read to measure the second output voltage of the audio device under test. The switch is kept in an off state, and the frequency of the adjusting signal generator is changed from 20Hz to 20kHz, at the moment, the frequency point for measuring the input impedance of the audio equipment is in a straight section of the frequency response. If the second output voltage is equal to one-half of the first output voltage, it can be determined that the measured modulus of the input impedance of the audio device under test is equal to its nominal value. I.e. indicating that the nominal value is accurate.
According to the measurement and calibration device and the measurement and calibration method for the input impedance of the audio equipment, the first output voltage of the audio equipment to be tested is measured when the switch device is closed through the first alternating-current millivoltmeter; when the audio equipment to be measured works in a frequency response straight section, according to the principle that the gain of a linear interval is constant, the output voltage is halved when the input voltage is halved, otherwise, the input voltage is halved when the output voltage is halved, if the second output voltage is equal to one half of the first output voltage, the modulus of the input impedance of the audio equipment to be measured is equal to the nominal value of the input impedance of the audio equipment to be measured, the measurement and verification process fully utilizes the principle that the gain of the audio equipment to work in the linear interval is unchanged, the online measurement and verification of the input impedance are realized, data can be directly read, and the method has the advantages of high efficiency, simple operation method and difficulty in error in the process.
EXAMPLE five
The audio equipment gain measuring device can be further extended on the basis of the measuring device, and can measure the unbalanced input impedance of the audio equipment by using the principle that the gain of the audio equipment is constant in the linear region when the audio equipment works.
As shown in fig. 5, the audio device input impedance measuring apparatus according to the embodiment of the present invention may include:
an audio signal generator S, a first alternating current millivoltmeter U1, a duplex variable resistance box (R1, R2);
the positive output end of the audio signal generator S is connected with the first input end of a duplex variable resistance box (R1, R2), the negative output end of the audio signal generator S is connected with the second input end of the duplex variable resistance box (R1, R2), the first output end of the duplex variable resistance box (R1, R2) is connected with the positive input end of the audio equipment to be tested with balanced input impedance, and the second output end of the duplex variable resistance box (R1, R2) is connected with the negative input end of the audio equipment to be tested; the output end of the audio equipment is connected with a rated load, and the first alternating current millivoltmeter is connected in parallel at two ends of the rated load so as to measure the output voltage of the tested audio equipment.
The first alternating-current millivoltmeter U1 measures the output voltage of the audio equipment to be tested, wherein the first output voltage of the audio equipment to be tested comprises the first output voltage when the resistance values of the duplex variable resistance boxes (R1 and R2) are set to zero; and a second output voltage of the audio equipment to be tested after the resistance values of the duplex variable resistance boxes (R1, R2) are adjusted; the second output voltage is half of the first output voltage, and the modulus of the input impedance of the audio equipment to be tested is the sum of the resistance values of the duplex variable resistance boxes (R1, R2) corresponding to the second output voltage, namely Ri＝R1+R2。
The dual-connection variable resistance box can be realized based on two variable resistance boxes of the same type, and the two variable resistance boxes of the same type are linked, namely, when the resistance value of one variable resistance box is adjusted, the resistance value of the other variable resistance box is changed by the same magnitude value at the same time.
The audio device of the present embodiment employs balanced input. The input impedance of the audio equipment is unknown, and the input impedance of the audio equipment can be measured by adopting the audio equipment input impedance measuring device.
The present embodiment is different from the first embodiment in that a double variable resistance box (R1, R2) is used instead of the variable resistance box R of the first embodiment. Correspondingly, the difference between the audio device input impedance measuring method based on the audio device input impedance measuring apparatus of the present embodiment and the second embodiment is that when the resistance values of the duplex variable resistance boxes (R1, R2) are adjusted, the present embodiment needs to perform linkage adjustment on R1 and R2. Other contents of this embodiment are the same as those of the first embodiment, and other contents of the audio device input impedance measurement method based on this embodiment are the same as those of the first embodiment, and are not described herein again.
EXAMPLE six
As shown in fig. 6, an embodiment of the present invention further provides an audio device input impedance measurement verification apparatus, which may include:
the audio signal generator S, a first alternating current millivoltmeter U1, a duplex resistor (R1, R2), a first switch device K1 and a second switch device K2;
the positive output end of audio signal generator S is connected the first input end of pair resistance (R1, R2), audio signal generator S 'S negative output end is connected the second input end of pair resistance (R1, R2), the first output end of pair resistance (R1, R2) is connected the positive input end of the audio equipment that awaits measuring that input impedance is balanced, the second output end of pair resistance (R1, R2) is connected the negative positive input end of audio equipment that awaits measuring, first exchange millivoltmeter U1 with the rated load R of the audio equipment' S that awaits measuring output endLThe output end of the audio equipment is connected with a rated load in parallel, and the first alternating current millivoltmeter is connected at two ends of the rated load in parallel to measure the output voltage of the tested audio equipment. The first switching device is bridged between the positive output end of the audio signal generator S and the positive input end of the audio equipment to be tested, and the second switching device is bridged between the negative output end of the audio signal generator S and the negative input end of the audio equipment to be tested; the sum of the resistance values of the duplex resistors (R1, R2) is equal to the measured modulus of the input impedance of the audio equipment to be tested, and can also be equal to the nominal value of the input impedance of the audio equipment;
the first alternating current millivoltmeter U1 measures the output voltage of the audio equipment to be tested, wherein the first output voltage of the audio equipment to be tested when the first switching device K1 and the second switching device K2 are both closed is included; and a second output voltage of the audio device under test when both the first switching device K1 and the second switching device K2 are off; if the second output voltage is equal to one half of the first output voltage, the sum of the resistance values of the double resistors (R1, R2) can be determined to be equal to the nominal value of the input impedance of the audio equipment to be tested.
The present embodiment may perform a measurement check of the input impedance for an audio device that employs a balanced input where the input impedance is known.
The difference between this embodiment and the third embodiment is that a duplex resistor (R1, R2) is used in this embodiment instead of the resistor R in the third embodiment, and correspondingly, two switches K1 and K2 are used in this embodiment, and are respectively connected in parallel with R1 and R2 of the duplex resistor. The difference between the audio device input impedance measurement verification method based on the audio device input impedance measurement verification apparatus of the present embodiment and the second embodiment is that when the switch device is controlled, the first switch device K1 and the second switch device K2 need to be controlled in an interlocking manner, that is, the first switch device K1 and the second switch device K2 are opened and closed simultaneously. The other contents in this embodiment are the same as those in the fourth embodiment, and the other contents of the audio device input impedance measurement and verification method based on this embodiment are the same as those in the fourth embodiment, and are not described herein again.
The device for measuring and verifying the input impedance of the audio equipment measures the first output voltage of the audio equipment to be tested when the first switching device and the second switching device are both closed through the first alternating-current millivoltmeter; and a second output voltage of the audio equipment to be tested when the first switching device and the second switching device are both switched off; when the audio equipment to be measured works in a frequency response straight section, according to the principle that the gain of a linear interval is constant, the output voltage is halved when the input voltage is halved, otherwise, the input voltage is halved when the output voltage is halved, if the second output voltage is equal to one half of the first output voltage, the modulus of the input impedance of the audio equipment to be measured is equal to the nominal value of the input impedance of the audio equipment to be measured, the measurement and verification process fully utilizes the principle that the gain of the audio equipment to work in the linear interval is unchanged, the online measurement and verification of the input impedance are realized, data can be directly read, and the method has the advantages of high efficiency, simple operation method and difficulty in error in the process.
EXAMPLE seven
As shown in fig. 7, the present embodiment provides an impedance measuring method of an input impedance measuring apparatus of an audio device, which may include the following steps:
s31, setting the resistance values of two resistors of the duplex variable resistance box to zero, and adjusting the output voltage of the signal generator to enable the tested audio equipment to be under the standard measurement condition;
s32, finding out the middle point frequency point of the frequency response straight section under the standard measuring condition, taking the frequency point as the testing frequency point for measuring the input impedance of the audio equipment, and reading the first output voltage of the first alternating current millivoltmeter;
s33, synchronously adjusting the resistance values of two resistors of the duplex variable resistance box to increase the resistance value of the duplex variable resistance box, and reading a second output voltage of the first alternating-current millivoltmeter;
and S34, when the second output voltage is half of the first output voltage, and the test frequency point is still in a straight section of frequency response, taking the sum of the current resistance values of the two resistors of the duplex variable resistance box as the mode of the input impedance of the audio equipment to be tested.
The audio device input impedance measuring method can be implemented based on the audio device input impedance measuring apparatus in the fifth embodiment, and the embodiments of each element for implementing the audio device input impedance measuring method are not described herein again. The connection is as shown in fig. 5, and the audio device of the present embodiment employs a balanced input. The input impedance of the audio equipment is unknown, and the input impedance of the audio equipment can be measured by adopting the audio equipment input impedance measuring device. The output end of the audio equipment is connected with a rated load, and the first alternating current millivoltmeter is connected in parallel at two ends of the rated load so as to measure the output voltage of the tested audio equipment.
After the resistance values of the duplex variable resistance boxes (R1, R2) are set to zero, the output voltage of the signal generator can be adjusted, the audio equipment to be tested is placed under a standard measurement condition, specifically, the frequency of the signal generator can be adjusted to change from 20Hz to 20kHz, an intermediate frequency point (for example, 1kHz, but not limited to 1kHz) of a frequency response straight section is found out by reading the measurement voltage of the first alternating-current millivolt meter, the frequency point is taken as a frequency point for measuring the input impedance of the audio equipment, and the output voltage of the audio equipment to be tested under the standard measurement condition is read and recorded as a first output voltage. Then, the resistance values of the resistor R1 and the resistor R2 in the duplex variable resistance boxes (R1, R2) can be synchronously adjusted to enable the resistance values of the resistor R1 and the resistor R2 to be synchronously increased, and the second output voltage of the audio equipment to be tested measured by the first alternating current millivoltmeter is read and recorded until the output voltage of the audio equipment to be tested is half of the first output voltage, and the record is read and recorded. Maintaining the resistance values of R1 and R2, the frequency of the tuning signal generator is varied from 20Hz to 20kHz, at which point the frequency used to measure the input impedance of the audio device should lie within the flat segment of the frequency response. And when the second output voltage is half of the first output voltage, reading the current resistance values of R1 and R2, and taking the sum of the current resistance values as the modulus of the input impedance of the audio equipment to be tested.
According to the device and the method for measuring the input impedance of the audio equipment, the first output voltage of the audio equipment to be measured is measured when the resistance value of the duplex variable resistance box is zero through the first alternating-current millivoltmeter; the resistance value of the duplex variable resistance box is adjusted to obtain a second output voltage of the audio equipment to be tested; when the audio equipment to be tested works in the frequency response straight section, according to the principle that the gain of a linear interval is constant, the output voltage is halved when the input voltage is halved, and conversely, the input voltage is halved when the output voltage is halved. When the resistance value of the variable resistance box is equal to the modulus of the input impedance of the audio equipment to be measured, the reading of the first alternating current millivoltmeter is halved, so that the modulus of the input impedance of the audio equipment to be measured can be directly read through the duplex variable resistance box, the measurement process fully utilizes the principle that the gain of the audio equipment working in a linear region is unchanged, the input impedance measurement is realized, the data can be directly read, and the method has the advantages of high efficiency, simple operation method and difficulty in error in the process.
Example eight
As shown in fig. 8, the present embodiment provides an impedance measurement verification method for an input impedance measurement apparatus of an audio device, which may include the following steps:
s41, closing the first switch device and the second switch device at the same time, adjusting the output voltage of the signal generator, and enabling the audio equipment to be tested to be under the standard measurement condition;
s42, finding out a midpoint frequency point of the frequency response straight section under the standard measurement condition, taking the frequency point as a frequency point for measuring the input impedance of the audio equipment, and measuring the first output voltage of the audio equipment to be measured through a first alternating current millivoltmeter;
s43, simultaneously disconnecting the first switch device and the second switch device, and measuring a second output voltage of the audio equipment to be tested through the first alternating current millivoltmeter;
s44, if the second output voltage is equal to one-half of the first output voltage, determining that the modulus of the input impedance of the audio device to be tested is equal to the measured value of the input impedance of the audio device to be tested.
The audio device input impedance measurement and verification method may be implemented based on the audio device input impedance measurement apparatus according to the sixth embodiment, and embodiments of each element that performs the audio device input impedance measurement and verification method are not described herein again. Connected as shown in fig. 6, the audio device employs balanced inputs. The output end of the audio equipment is connected with a rated load, and the first alternating current millivoltmeter is connected in parallel at two ends of the rated load so as to measure the output voltage of the tested audio equipment.
In one embodiment, the output voltage of the signal generator may be adjusted to place the audio device under test in standard measurement conditions. Specifically, the frequency of the signal generator may be adjusted to vary from 20Hz to 20kHz, an intermediate frequency point (for example, 1kHz, but not limited to 1kHz) of the frequency response straight segment is found by reading the measurement voltage of the first ac millivoltmeter, the intermediate frequency point is used as a frequency point for measuring the input impedance of the audio device, and the output voltage of the audio device to be measured under the standard measurement condition is read and recorded as the first output voltage. Then, the first switching device and the second switching device can be synchronously switched off, and the second output voltage of the audio equipment to be tested measured by the first alternating current millivoltmeter can be read and recorded. Keeping the first switching means and the second switching means in an open state, the frequency of the adjustment signal generator is changed from 20Hz to 20kHz, at which time the frequency point for measuring the input impedance of the audio device should be within the flat segment of the frequency response. If the second output voltage is equal to one-half of the first output voltage, it can be determined that the measured modulus of the input impedance of the audio device under test is equal to its nominal value. I.e. indicating that the measured values are accurate.
According to the device and the method for measuring and checking the input impedance of the audio equipment, the first output voltage of the audio equipment to be tested is measured when the first switch device and the second switch device are synchronously closed and the second output voltage of the audio equipment to be tested is measured when the first switch device and the second switch device are synchronously disconnected through the first alternating-current millivoltmeter; when the audio equipment to be measured works in a frequency response straight section, according to the principle that the gain of a linear interval is constant, the output voltage is halved when the input voltage is halved, otherwise, the input voltage is halved when the output voltage is halved, if the second output voltage is equal to one half of the first output voltage, the modulus of the input impedance of the audio equipment to be measured is equal to the nominal value of the input impedance of the audio equipment to be measured, the measurement and verification process fully utilizes the principle that the gain of the audio equipment to work in the linear interval is unchanged, the online measurement and verification of the input impedance are realized, data can be directly read, and the method has the advantages of high efficiency, simple operation method and difficulty in error in the process.
The invention has the following advantages:
the invention selects and switches the optimal access resistance to measure in the measuring process, and the data acquisition is not in the measured part of the audio equipment, but in the output end of the audio equipment, the data acquisition is isolated from the measured part (input end), thereby avoiding the shunting action of the input impedance of the alternating-current millivoltmeter on the input signal current and avoiding the measurement error. And the modulus of the input impedance of the audio device can be read directly from the variable resistance box.
The reactive component of the access resistance and the input resistance of the audio device changes the output frequency response of the audio device due to the presence of the access resistance during the measurement process. Therefore, it is proposed that the middle frequency point of the frequency response straight section needs to be found under the standard measurement condition, the frequency point is used as the frequency point for measuring the input impedance of the audio device, and the frequency response is compared before and after the resistor is connected in the measurement process to confirm whether the used measurement frequency point is in the frequency response straight section. The accuracy of the input impedance is improved.
The mode of the input impedance measured by using the variable resistance box can be changed into a fixed resistance, and the measurement and verification method and the device are used for verifying.
The present invention can measure the input impedance of the unbalanced input terminal and the input impedance of the balanced input terminal of the audio device.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims (18)

1. An audio device input impedance measurement apparatus, comprising:
the audio signal generator, the first alternating current millivoltmeter and the variable resistance box;
the signal output end of the audio signal generator is connected to the unbalanced signal input end of the audio equipment to be tested through the variable resistance box, the ground input end of the audio equipment to be tested is connected with the ground output end of the audio signal generator, the first alternating-current millivoltmeter is connected with the output end of the audio equipment to be tested, and the output end of the audio equipment to be tested is connected with a rated load; the audio equipment to be tested is placed under a standard measurement condition;
the first alternating-current millivoltmeter is used for measuring the output voltage of the audio equipment to be tested, wherein the first output voltage of the audio equipment to be tested is obtained by setting the resistance value of the variable resistance box to zero; the resistance value of the variable resistance box is adjusted to obtain a second output voltage of the audio equipment to be tested; when the second output voltage is half of the first output voltage, the mode of the input impedance of the audio equipment to be tested corresponds to the resistance value of the variable resistance box; the frequency point when measuring the first output voltage is the middle frequency point of the frequency response straight section, the frequency point when measuring the second output voltage is still in the frequency response straight section, and the frequency point when measuring the first output voltage is consistent with the frequency point when measuring the second output voltage.
2. The audio device input impedance measurement apparatus of claim 1, further comprising:
a second alternating current millivoltmeter connected between the signal output end of the audio signal generator and the ground output end of the audio signal generator in a bridging mode;
and when the resistance value of the variable resistance box is before and after the resistance value is changed, the reading of the second alternating-current millivoltmeter is unchanged.
3. The audio device input impedance measuring apparatus of claim 2, wherein the input impedance of the second ac millivoltmeter is substantially larger than the output impedance of the audio signal generator, the input impedance of the first ac millivoltmeter is substantially larger than the output impedance of the audio device to be tested, and the output impedance of the audio signal generator is substantially smaller than the input impedance of the audio device.
4. An impedance measuring method based on the audio device input impedance measuring apparatus according to any one of claims 1 to 3, characterized by comprising the steps of:
setting the resistance value of the variable resistance box to zero, and adjusting the output voltage of the signal generator to enable the tested audio equipment to be placed under the standard measurement condition;
finding out a midpoint frequency point of a frequency response straight section under the standard measurement condition, taking the frequency point as a test frequency point for measuring the input impedance of the audio equipment, and reading a first output voltage of a first alternating-current millivoltmeter;
adjusting the resistance value of the variable resistance box to increase the resistance value of the variable resistance box, and reading a second output voltage of the first alternating-current millivoltmeter;
and when the second output voltage is half of the first output voltage and the test frequency point is still in a straight section of frequency response, taking the current resistance value of the variable resistance box as a mode of the input impedance of the audio equipment to be tested.
5. An audio device input impedance measurement verification apparatus, comprising:
the audio signal generator, the first alternating current millivoltmeter, the resistor and the switching device;
the signal output end of the audio signal generator is connected with the unbalanced signal input end of the audio equipment to be tested through the resistor, the ground input end of the audio equipment to be tested is connected with the ground output end of the audio signal generator, the first alternating-current millivoltmeter is connected with the output end of the audio equipment to be tested, and the output end of the audio equipment is connected with a rated load; the switching device is bridged at two ends of the resistor; the resistance value of the resistor is equal to the modulus of the measured input impedance of the audio equipment to be tested;
the first alternating-current millivoltmeter measures the output voltage of the audio equipment to be tested, wherein the first output voltage of the audio equipment to be tested when the switching device is closed is included; and a second output voltage of the audio equipment to be tested when the switching device is switched off; if the second output voltage is equal to one half of the first output voltage, the resistance value of the resistor is equal to the modulus of the input impedance of the audio equipment to be tested.
6. The audio device input impedance measurement verification apparatus of claim 5, further comprising:
a second alternating current millivoltmeter connected between the signal output end of the audio signal generator and the ground output end of the audio signal generator in a bridging mode;
and when the resistance value of the variable resistance box is before and after the resistance value is changed, the reading of the second alternating current millivoltmeter is unchanged.
7. The audio device input impedance measurement verification apparatus according to claim 6, wherein the input impedance of the second ac millivoltmeter is substantially larger than the output impedance of the audio signal generator, the input impedance of the first ac millivoltmeter is substantially larger than the output impedance of the audio device to be tested, and the output impedance of the audio signal generator is substantially smaller than the input impedance of the audio device.
8. An impedance measurement verification method based on the audio device input impedance measurement verification apparatus of any one of claims 5 to 7, characterized by comprising the steps of:
closing the switch device, and adjusting the output voltage of the signal generator to enable the tested audio equipment to be placed under the standard measurement condition;
finding out a midpoint frequency point of the frequency response straight section under the standard measurement condition, taking the frequency point as a frequency point for measuring the input impedance of the audio equipment, and measuring a first output voltage of the audio equipment to be measured through a first alternating current millivoltmeter;
switching off the switching device, and measuring a second output voltage of the audio equipment to be tested through a first alternating-current millivoltmeter, wherein the test frequency point is still in a straight section of frequency response;
and if the second output voltage is equal to one half of the first output voltage and the test frequency point is still in a straight section of frequency response, judging that the modulus of the input impedance of the audio equipment to be tested is equal to the resistance value of the resistor.
9. An audio device input impedance measurement apparatus, comprising:
the audio signal generator, the first alternating current millivoltmeter and the duplex variable resistance box;
the signal output end of the audio signal generator is a balanced output end, the positive balanced signal output end of the audio signal generator is connected with the first input end of the duplex variable resistance box, the negative balanced signal output end of the audio signal generator is connected with the second input end of the duplex variable resistance box, the first output end of the duplex variable resistance box is connected with the positive end of the balanced input end of the audio equipment to be tested, and the second output end of the duplex variable resistance box is connected with the negative end of the balanced input end of the audio equipment to be tested; the audio equipment to be tested is placed under a standard measurement condition;
the first alternating-current millivoltmeter measures the output voltage of the audio equipment to be tested, wherein the first output voltage of the audio equipment to be tested comprises the first output voltage when the resistance value of the duplex variable resistance box is set to be zero; the resistance value of the duplex variable resistance box is adjusted to obtain a second output voltage of the audio equipment to be tested; when the second output voltage is half of the first output voltage, the modulus of the input impedance of the audio equipment to be tested is the sum of the resistance values of the corresponding duplex variable resistance boxes; the frequency point when measuring the first output voltage is the middle frequency point of the frequency response straight section, the frequency point when measuring the second output voltage is still in the frequency response straight section, and the frequency point when measuring the first output voltage is consistent with the frequency point when measuring the second output voltage.
10. The audio device input impedance measurement apparatus of claim 9, further comprising:
a second alternating current millivoltmeter which is bridged between the positive balanced output terminal of the audio signal generator and the negative balanced output terminal of the audio signal generator, wherein the signal input end of the alternating current millivoltmeter is a balanced input end;
and when the resistance value of the duplex variable resistance box is before and after the resistance value is changed, the reading of the second alternating-current millivoltmeter is unchanged.
11. The audio device input impedance measuring apparatus of claim 10, wherein the input impedance of the second ac millivoltmeter is substantially larger than the output impedance of the balanced output terminal of the audio signal generator, the input impedance of the first ac millivoltmeter is substantially larger than the output impedance of the audio device to be tested, and the output impedance of the audio signal generator is substantially smaller than the input impedance of the audio device.
12. An impedance measuring method based on the audio device input impedance measuring apparatus according to any one of claims 9 to 11, comprising the steps of:
setting the resistance values of two resistors of the duplex variable resistance box to zero, and adjusting the output voltage of the signal generator to enable the tested audio equipment to be placed under the standard measurement condition;
finding out a midpoint frequency point of a frequency response straight section under the standard measurement condition, taking the frequency point as a test frequency point for measuring the input impedance of the audio equipment, and reading a first output voltage of a first alternating-current millivoltmeter;
synchronously adjusting the resistance values of two resistors of the duplex variable resistance box to increase the resistance value of the duplex variable resistance box, and reading a second output voltage of the first alternating-current millivoltmeter;
and when the second output voltage is half of the first output voltage and the test frequency point is still within the straight section of the frequency response, taking the sum of the current resistance values of the two resistors of the duplex variable resistance box as the mode of the input impedance of the audio equipment to be tested.
13. An audio device input impedance measurement verification apparatus, comprising:
the audio signal generator, the first alternating current millivoltmeter, the first resistor, the second resistor, the first switching device and the second switching device;
the positive output end of the balanced output of the audio signal generator is connected with the first input end of the first resistor, the negative output end of the balanced output of the audio signal generator is connected with the second input end of the second resistor, the first output end of the duplex variable resistor box is connected with the positive end of the balanced input end of the audio equipment to be tested, and the second output end of the duplex variable resistor box is connected with the negative end of the balanced input end of the audio equipment to be tested; the first alternating-current millivoltmeter is connected with the output end of the audio equipment to be tested, and the output end of the audio equipment is connected with a rated load; the first switch device is connected in parallel to the first resistor, and the second switch device is connected in parallel to the second resistor; the duplex first switch and the second switch are duplex linked switches; the sum of the resistance values of the first resistor and the second resistor is equal to the modulus of the measured input impedance of the audio equipment to be tested, and the resistance value of the first resistor is equal to the resistance value of the second resistor;
the first alternating-current millivoltmeter measures the output voltage of the audio equipment to be tested, wherein the first output voltage of the audio equipment to be tested when the first switch device and the second switch device are both closed is included; and a second output voltage of the audio equipment to be tested when the first switching device and the second switching device are both switched off; if the second output voltage is equal to one half of the first output voltage, the sum of the resistance value of the first resistor and the resistance value of the second resistor is equal to the modulus of the input impedance of the audio equipment to be tested.
14. The audio device input impedance measurement verification apparatus of claim 13, further comprising:
a second alternating current millivoltmeter connected between the signal output end of the audio signal generator and the ground output end of the audio signal generator in a bridging mode;
and when the resistance value of the variable resistance box is before and after the resistance value is changed, the reading of the second alternating-current millivoltmeter is unchanged.
15. The audio device input impedance measurement verification apparatus according to claim 14, wherein the input impedance of the second millivoltmeter is substantially larger than the output impedance of the audio signal generator, the input impedance of the first millivoltmeter is substantially larger than the output impedance of the audio device to be tested, and the output impedance of the audio signal generator is substantially smaller than the input impedance of the audio device.
16. An impedance measurement verification method based on the audio device input impedance measurement verification apparatus according to any one of claims 13 to 15, comprising the steps of:
closing the first switch device and the second switch device at the same time, and adjusting the output voltage of the signal generator to enable the tested audio equipment to be placed under the standard measurement condition;
finding out a midpoint frequency point of the frequency response straight section under the standard measurement condition, taking the frequency point as a frequency point for measuring the input impedance of the audio equipment, and measuring a first output voltage of the audio equipment to be measured through a first alternating current millivoltmeter;
simultaneously disconnecting the first switching device and the second switching device, and measuring a second output voltage of the audio equipment to be tested through a first alternating current millivoltmeter;
and if the second output voltage is equal to one half of the first output voltage and the test frequency point is still in a straight section of frequency response, judging that the modulus of the input impedance of the audio equipment to be tested is equal to the sum of the current resistance values of the first resistor and the second resistor.
17. A computer device comprising a memory and a processor, the memory storing a computer program, characterized in that the processor, when executing the computer program, implements the steps of the method of any one of claims 4, 8, 12 and 16.
18. A computer-readable storage medium, on which a computer program is stored, which, when being executed by a processor, carries out the steps of the method of any one of claims 4, 8, 12 and 16.
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CN108169566A (en) * 2017-12-29 2018-06-15 江苏海湾电气科技有限公司 Online testing impedance circuit and method
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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5345182A (en) * 1991-10-31 1994-09-06 Hewlett-Packard Company Impedance meter capable of performing measurements at high precision over wide impedance and frequency ranges
CN1842712A (en) * 2001-09-06 2006-10-04 东京毅力科创株式会社 Impedance measuring circuit, its method, and capacitance measuring circuit
CN202013381U (en) * 2011-03-11 2011-10-19 湖州师范学院 Partial pressure resistor measuring unit
CN103439578A (en) * 2013-08-30 2013-12-11 昆山奥德鲁自动化技术有限公司 Impedance measurement circuit
CN106060749A (en) * 2016-06-14 2016-10-26 王健 Calibration method for impedance test of electroacoustic device
CN106162484A (en) * 2015-04-16 2016-11-23 展讯通信（上海）有限公司 A kind of earphone impedance detecting system, method and portable electric appts

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5345182A (en) * 1991-10-31 1994-09-06 Hewlett-Packard Company Impedance meter capable of performing measurements at high precision over wide impedance and frequency ranges
CN1842712A (en) * 2001-09-06 2006-10-04 东京毅力科创株式会社 Impedance measuring circuit, its method, and capacitance measuring circuit
CN202013381U (en) * 2011-03-11 2011-10-19 湖州师范学院 Partial pressure resistor measuring unit
CN103439578A (en) * 2013-08-30 2013-12-11 昆山奥德鲁自动化技术有限公司 Impedance measurement circuit
CN106162484A (en) * 2015-04-16 2016-11-23 展讯通信（上海）有限公司 A kind of earphone impedance detecting system, method and portable electric appts
CN106060749A (en) * 2016-06-14 2016-10-26 王健 Calibration method for impedance test of electroacoustic device

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
两种半偏法测电阻;谭喜强;《物理教学探讨》;20070510;第25卷(第291期);第26页第2节 *
电阻测量的方法设计与实验探究;田水云等;《铜仁学院学报》;20160731;第18卷(第4期);第50-53页 *

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