A device and method for measuring the amplification factor and phase shift of a voltage amplifier

Abstract

The present invention provides a device and method for measuring the amplification factor and phase shift of a voltage amplifier, belonging to the field of impedance measurement. The device includes: an isolation transformer, an inductive shunt, a comparison circuit, a measurement circuit, a sampling unit, a calculation unit and a power supply; the isolation transformer includes an input end and two output ends; its input end is connected to the power supply; the two output ends are respectively connected in series in the comparison circuit and the measurement circuit; the inductive shunt includes a first winding and a second winding; the first end of the first winding is connected to the current input end of the comparison circuit, and the tail end is connected to the current output end of the comparison circuit; the first end of the second winding is connected to the current output end of the measurement circuit, and the tail end is connected to the current input end of the measurement circuit; the sampling unit is respectively connected to the comparison circuit, the measurement circuit, and the calculation unit. The present invention can accurately measure the amplification factor and phase shift of the voltage amplifier, and has traceability.

Description

Technical Field

[0001] The invention belongs to the field of impedance (high voltage and low voltage) measurement, and in particular relates to a device and a method for measuring the amplification factor and phase shift of a voltage amplifier. Background Art

[0002] The sampling method is usually used to measure the gain and phase shift of the voltage amplifier, that is, by sampling and measuring the voltage signals at the input and output of the voltage amplifier, the gain and phase shift are calculated based on the sampled data. However, this method requires that the input and output voltages of the voltage amplifier are large enough, that is, to meet the sampling accuracy requirements. If the voltage signal is too small, such as below 20mV, the sampling accuracy cannot be guaranteed, and the gain and phase shift of the voltage amplifier cannot be obtained.

[0003] In addition, the current measurement method does not have traceability. Traceability means that the value can be directly or indirectly traced back to the national basic standard through the uncertainty chain, which can make the measurement result more accurate. Because the current voltage amplifier circuit amplification factor and phase shift measurement are often directly measured using an oscilloscope, it does not have traceability, and it is impossible to measure the uncertainty of the amplification factor and phase shift, and it is impossible to make the measurement result more accurate. Summary of the invention

[0004] The purpose of the present invention is to solve the problems existing in the above-mentioned prior art and to provide a device and method for measuring the amplification factor and phase shift of a voltage amplifier. When the voltage signal at the input end of the voltage amplifier is small, the amplification factor and phase shift can be accurately measured and the device and method have traceability.

[0005] The present invention is achieved through the following technical solutions:

[0006] A device for measuring the amplification factor and phase shift of a voltage amplifier, the device for measuring the amplification factor and phase shift of a voltage amplifier comprising: an isolation transformer, an inductive shunt, a comparison circuit, a measurement circuit, a sampling unit, a calculation unit and a power supply;

[0007] The isolation transformer comprises an input end and two output ends; the input end is connected to the power supply; the two output ends are respectively connected in series in the comparison circuit and the measurement circuit;

[0008] The inductive shunt comprises a first winding and a second winding; the first winding has a head end connected to a current input end of the comparison loop, and a tail end connected to a current output end of the comparison loop; the second winding has a head end connected to a current output end of the measurement loop, and a tail end connected to a current input end of the measurement loop;

[0009] The sampling unit is connected to the comparison circuit, the measurement circuit and the calculation unit respectively.

[0010] Specifically, the comparison circuit includes a comparison circuit second standard resistor R connected in series 2 ', compare the first standard resistor R 1 , the first winding of the inductive shunt, and the first output end of the isolation transformer, the four are connected to form a loop;

[0011] The measuring circuit comprises a first standard resistor R connected in series with the measuring circuit 1 ', measure the circuit with the second standard resistor R 2 , the second winding of the inductive shunt, and the second output end of the isolation transformer, the four are connected to form a loop;

[0012] The two ends of the voltage amplifier to be measured are respectively connected to the measurement circuit with a second standard resistor R 2 The two voltage measurement terminals are connected.

[0013] The turns ratio of the first winding to the second winding is 1:1.

[0014] The sampling unit includes a first sampling voltmeter and a second sampling voltmeter;

[0015] The two ends of the first sampling voltage meter are respectively connected to the first standard resistor R 1 The two voltage measurement terminals are connected;

[0016] Two ends of the second sampling voltmeter are respectively connected to two voltage measuring ends of the voltage amplifier to be measured.

[0017] The sampling unit further includes a sampling trigger;

[0018] The sampling trigger is connected to the external triggering end of the first sampling voltmeter and the second sampling voltmeter respectively.

[0019] The calculation unit is connected to the sampling trigger, the first sampling voltmeter, and the second sampling voltmeter respectively.

[0020] The comparison circuit uses a first standard resistor R 1 The first standard resistor R 1 The resistance values ​​of ′ are equal;

[0021] The comparison circuit uses a second standard resistor R 2 ' and the second standard resistor R used in the measurement circuit 2 The resistance values ​​are equal;

[0022] The comparison circuit uses a first standard resistor R 1 It is the second standard resistor R used in the measurement circuit. 2 K times the resistance value;

[0023] The K is equal to the nominal value of the voltage amplifier to be tested.

[0024] Further, the device of the present invention comprises a lock-in amplifier;

[0025] The lock-in amplifier comprises a Lock-in terminal, an A terminal and a B terminal;

[0026] The Lock-in terminal of the lock-in amplifier is connected to the reference winding Ref of the isolation transformer;

[0027] The A terminal of the lock-in amplifier is connected to the first winding of the inductive shunt;

[0028] The B terminal of the lock-in amplifier is connected to the second winding of the inductive shunt.

[0029] The present invention also provides a method for measuring the amplification factor and phase shift of a voltage amplifier, such as Figure 2 As shown, the method includes:

[0030] (1) Connect the input end of the isolation transformer to the power supply;

[0031] (2) Constructing a comparison circuit: Use the second standard resistor R 2 ', compare the first standard resistance R in the circuit 1 , the first winding of the inductive shunt, and the first output end of the isolation transformer are connected in series in sequence to form a comparison loop; wherein the head end of the first winding of the inductive shunt is connected to the current input end of the comparison loop, and the tail end of the first winding is connected to the current output end of the comparison loop;

[0032] (3) Construct the measurement circuit: Connect the measurement circuit with the first standard resistor R 1 ', measure the circuit with the second standard resistor R 2 , the second winding of the inductive shunt, and the second output end of the isolation transformer are connected in series in sequence to form a measurement loop; wherein the head end of the second winding of the inductive shunt is connected to the current output end of the measurement loop, and the tail end of the second winding is connected to the current input end of the measurement loop;

[0033] (4) Connect the voltage amplifier to be tested: Connect the two ends of the voltage amplifier to the measurement circuit with the second standard resistor R 2 The two voltage measurement terminals are connected;

[0034] (5) Connect the sampling unit: Connect the two ends of the first sampling voltmeter to the first standard resistor R 1 connecting the two voltage measuring terminals of the second sampling voltmeter to the two voltage measuring terminals of the voltage amplifier to be measured; connecting the two terminals of the second sampling voltmeter to the two voltage measuring terminals of the voltage amplifier to be measured;

[0035] (6) Connecting a sampling trigger and a computing unit: connecting the sampling trigger to the external trigger terminals of the first sampling voltmeter and the second sampling voltmeter respectively; connecting the computing unit to the sampling trigger, the first sampling voltmeter, and the second sampling voltmeter respectively;

[0036] (7) Synchronous sampling to obtain voltage value: synchronously sampling the first sampling voltmeter and the second sampling voltmeter to obtain the voltage value on the first sampling voltmeter The voltage value on the second sampling voltmeter

[0037] (8) Calculate the amplification factor A of the voltage amplifier to be tested v And phase shift: using the voltage value on the first sampling voltmeter The voltage value on the second sampling voltmeter Get the amplification factor A of the voltage amplifier to be tested v and phase shift.

[0038] The operation of step (8) includes: using the following formula to calculate the amplification factor A of the voltage amplifier to be tested: v and phase shift

[0039]

[0040]

[0041] Among them, b 1 、a 1 yes The sine and cosine amplitudes, b 2 、a 2 yes Furthermore, there is an impedance adjustment step between step (6) and step (7), comprising:

[0042] (S1) connecting the Lock-in terminal of the lock-in amplifier to the reference winding Ref of the isolation transformer, connecting the A terminal of the lock-in amplifier to the first winding of the inductive shunt, and connecting the B terminal of the lock-in amplifier to the second winding of the inductive shunt;

[0043] (S2) Setting the lock-in amplifier to AB function;

[0044] (S3) Observe whether the display value of the lock-in amplifier is 0. If not, use the first standard resistor R 1 ' is connected in series or in parallel with a resistor, then returns to step (S3), if yes, then goes to step (S4);

[0045] (S4) Disconnect the Lock-in terminal of the phase-locked amplifier from the reference winding Ref of the isolation transformer, disconnect the A terminal of the phase-locked amplifier from the first winding of the inductive shunt, and disconnect the B terminal of the phase-locked amplifier from the second winding of the inductive shunt.

[0046] Compared with the prior art, the beneficial effect of the present invention is that when the voltage signal at the input end of the voltage amplifier is small, the present invention can accurately measure its amplification factor and phase shift, and has traceability. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 A schematic diagram of a device for measuring the amplification factor and phase shift of a voltage amplifier according to the present invention;

[0048] Figure 2 A flowchart of the steps of the method of the present invention.

[0049] Figure 3 A schematic diagram of an embodiment of the present invention; DETAILED DESCRIPTION

[0050] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0051] like Figure 1 As shown, the device for measuring the amplification factor and phase shift of a voltage amplifier of the present invention comprises: an isolation transformer 3 (T 1 ), inductive shunt 4 (T), comparison circuit 1, measurement circuit 2, sampling unit, calculation unit and power supply 8.

[0052] The isolation transformer 3 (T 1 ) includes an input terminal 301 and two output terminals 302, 303; the isolation transformer T 1 The input terminal 301 is connected to the power supply 8, and the isolation transformer T 1 The first output terminal 302 is connected in series in the comparison circuit 1 , and the second output terminal 303 is connected in series in the measurement circuit 2 .

[0053] The inductive shunt 4 (T) includes a first winding 401 and a second winding 402, wherein the head end of the first winding 401 is connected to the current input end of the comparison loop 1, and the tail end of the first winding 401 is connected to the current output end of the comparison loop 1; the head end of the second winding 402 is connected to the current output end of the measurement loop 2, and the tail end of the second winding 402 is connected to the current input end of the measurement loop 2.

[0054] The turns ratio of the first winding 401 and the second winding 402 is 1:1.

[0055] In this embodiment, the first winding 401 and the second winding 402 of the inductive shunt T are both 1000 turns, and the operating frequency is 50Hz to 1kHz. The core material is iron-based amorphous. The wound inductive shunt T is reversely connected to the circuit, that is, the head end of one winding and the tail end of the other winding are respectively used as the current input ends of the two loops. In this working state of T, the two windings are tightly twisted and wound on the same core, and the leakage inductance is small; the excitation impedance is very high, and the current ratio between the two loops is only determined by the excitation impedance of the inductive shunt itself; when the loads carried by the two loops are equal, since the currents flowing through the two windings of the shunt are opposite, the self-inductance voltage and mutual inductance voltage generated in each loop are offset each other, therefore, the inductive shunt only plays a shunt role, that is, providing two equal working currents for the circuit, and no voltage drop will be generated in the circuit.

[0056] Specifically, the comparison circuit 1 includes a comparison circuit second standard resistor R connected in series. 2 ', compare the first standard resistor R 1 , the first winding 401 of the inductive shunt T, the isolation transformer T 1 The first output terminal 302 of , the four are connected to form a loop.

[0057] The measuring circuit 2 comprises first standard resistors R connected in series. 1 ', measure the circuit with the second standard resistor R 2 , the second winding 402 of the inductive shunt T, the isolation transformer T 1 The second output terminal 303 of , the four are connected to form a loop.

[0058] The two ends of the voltage amplifier 7 to be tested (the first stage is a voltage follower, the input voltage is 1mV-100mV, and the output is less than 10V) are respectively connected to the second standard resistor R 2 The voltage measurement terminal is connected.

[0059] The sampling unit includes a first sampling voltmeter 5 and a second sampling voltmeter 6 (both of which can be digital multimeter 3458), and the two ends of the first sampling voltmeter 5 are respectively connected to the first standard resistor R 1 The two ends of the second sampling voltmeter 6 are connected to the two voltage measuring ends of the voltage amplifier to be measured, respectively.

[0060] The sampling unit further includes a sampling trigger, which is connected to the external triggering ends of the first sampling voltmeter 5 and the second sampling voltmeter 6 respectively, and the sampling trigger is used to control the first sampling voltmeter 5 and the second sampling voltmeter 6 to perform synchronous sampling.

[0061] The calculation unit is connected to the sampling trigger, the first sampling voltmeter 5, and the second sampling voltmeter 6 respectively, and calculates the amplification factor and phase shift of the voltage amplifier according to the sampling data of the first sampling voltmeter 5 and the second sampling voltmeter 6. The calculation unit can adopt a general-purpose computer, etc.

[0062] The principle of obtaining the amplification factor and phase shift of the voltage amplifier is as follows:

[0063] Use an inductive shunt to provide the same operating current for comparison loop 1 and measurement loop 2, where R 1 ≈R 1 ′,R 2 ≈R 2 ′, and K=R 1 / R 2 , K takes 10, 100 and 1000, which is the same as the nominal value of the voltage amplifier to be tested. For example, if the nominal value of the voltage amplifier to be tested is 10, then K takes 10; if the nominal value of the voltage amplifier to be tested is 100, then K takes 100, and so on. The measurement circuit uses the second standard resistor R 2 The two ends of the voltage amplifier 7 amplify the v times, the comparison circuit uses the first standard resistor R 1 The voltage at the output of the voltage amplifier is sampled synchronously, and the amplification factor and phase shift of the voltage amplifier are calculated using the two voltage values ​​obtained by sampling. The specific process is as follows:

[0064] When R 1 ≈R 1 ′,R 2 ≈R 2 ′ (because the input impedance of T is very high, greater than 80 kOhms, the current error is the ratio of the impedance difference between loop 1 and loop 2 to the input impedance), and R 1 =KR 2 Sometimes, there is (in, Respectively represent the current on the comparison loop 1 and the current on the measurement loop 2), so:

[0065]

[0066] in, is the voltage value on the first sampling voltmeter, is the voltage across the second standard resistor R2 used in the measurement circuit, is the voltage value on the second sampling voltmeter.

[0067] According to formula (2), the gain A of voltage amplifier 7 can be obtained as v The formula for the phase shift is:

[0068]

[0069]

[0070] Among them, b 1 、a 1 is the sampling voltage on the first sampling voltage meter 5 The sine and cosine amplitudes, b 2 、a 2 is the sampling voltage on the second sampling voltage meter 6 When a digital voltmeter samples an AC voltage signal, it obtains multiple cycles of DC voltage signals. Based on these voltage values ​​and existing algorithms, the amplitude and phase of the "AC voltage signal" can be calculated.

[0071] Furthermore, the device of the present invention includes a lock-in amplifier, which includes a lock-in terminal, an A terminal and a B terminal. The present invention uses the lock-in amplifier to adjust so that the impedance of the comparison loop 1 and the measurement loop 2 are substantially equal, that is, R 1 +R 2 ′≈R 2 +R 1 '. During adjustment, connect the Lock-in terminal of the phase-locked amplifier to the isolation transformer T 1 The reference winding Ref of the phase-locked amplifier is connected, the A terminal of the phase-locked amplifier is connected to the first winding 401 of the shunt T; the B terminal of the phase-locked amplifier is connected to the second winding 402 of the shunt T; the phase-locked amplifier is set to AB function, and the display value of the phase-locked amplifier is observed. If the display value of the phase-locked amplifier is not 0, then the R 1 ', and observe the display value of the phase-locked amplifier at the same time. Repeat this process several times until the display value of the phase-locked amplifier is 0. In this way, the impedance of the comparison loop 1 and the measurement loop 2 are basically equal by using the phase-locked amplifier. After adjustment (i.e. the display value of the phase-locked amplifier is 0), disconnect the ports connected to the phase-locked amplifier from the phase-locked amplifier, but keep the ports connected in series or in parallel with R 1 The lock-in amplifier no longer participates in the subsequent sampling process.

[0072] The present invention also provides a method for measuring the amplitude and phase shift of a voltage amplifier, such as Figure 2 As shown, the method includes:

[0073] (1) Connect the isolation transformer T 1 The input terminal 301 is connected to the power supply 8;

[0074] (2) Constructing comparison circuit 1: Use the second standard resistor R 2 ', compare the first standard resistor R 1, the first winding 401 of the inductive shunt T, the isolation transformer T 1 The first output terminals 302 of the inductive shunt 4 (T) are connected in series to form a comparison loop 1; wherein the head end of the first winding 401 of the inductive shunt 4 (T) is connected to the current input end of the comparison loop 1, and the tail end of the first winding 401 is connected to the current output end of the comparison loop 1;

[0075] (3) Constructing measurement loop 2: Connect the measurement loop to the first standard resistor R 1 ', measure the circuit with the second standard resistor R 2 , the second winding 402 of the inductive shunt T, the isolation transformer T 1 The second output terminals 303 of the inductive shunt 4 (T) are connected in series to form a measuring loop 2; wherein the head end of the second winding 402 of the inductive shunt 4 (T) is connected to the current output terminal of the measuring loop 2, and the tail end of the second winding 402 is connected to the current input terminal of the measuring loop 2;

[0076] (4) Connect the voltage amplifier to be tested: Connect the two ends of the voltage amplifier to be tested 7 to the measurement circuit with the second standard resistor R 2 The two voltage measurement terminals are connected;

[0077] (5) Connect the sampling unit: Connect the two ends of the first sampling voltmeter 5 to the first standard resistor R 1 The two voltage measuring terminals of the second sampling voltmeter 6 are connected to the two voltage measuring terminals of the voltage amplifier 7 to be measured;

[0078] (6) Connecting the sampling trigger and the calculation unit: connecting the sampling trigger to the external trigger terminals of the first sampling voltmeter 5 and the second sampling voltmeter 6 respectively; connecting the calculation unit to the sampling trigger, the first sampling voltmeter 5, and the second sampling voltmeter 6 respectively;

[0079] (7) Synchronous sampling to obtain voltage value: synchronously sampling the first sampling voltmeter and the second sampling voltmeter to obtain the voltage value on the first sampling voltmeter The voltage value on the second sampling voltmeter

[0080] (8) Calculate the gain and phase shift of the voltage amplifier to be tested: Use the voltage value on the first sampling voltmeter The voltage value on the second sampling voltmeter Obtain the amplification factor and phase shift of the voltage amplifier to be tested: Use formulas (3) and (4) to calculate the amplification factor and phase shift of the voltage amplifier to be tested.

[0081] Furthermore, there is an impedance adjustment step between step (6) and step (7), comprising:

[0082] (S1) Connect the Lock-in terminal of the lock-in amplifier to the isolation transformer T 1 The reference winding Ref is connected to the phase-locked amplifier, the A terminal of the phase-locked amplifier is connected to the first winding 401 of the shunt T, and the B terminal of the phase-locked amplifier is connected to the second winding 402 of the shunt T;

[0083] (S2) Setting the lock-in amplifier to AB function;

[0084] (S3) Observe whether the display value of the lock-in amplifier is 0. If not, use the first standard resistor R 1 ' is connected in series or in parallel with a resistor, then returns to step (S3), if yes, then goes to step (S4);

[0085] (S4) Connect the Lock-in terminal of the lock-in amplifier to the isolation transformer T 1 The reference winding Ref is disconnected, the A terminal of the phase-locked amplifier is disconnected from the first winding 401 of the shunt T, and the B terminal of the phase-locked amplifier is disconnected from the second winding 402 of the shunt T.

[0086] The lock-in amplifier in this embodiment is the American AMETEK 7280 lock-in amplifier.

[0087] Specifically, in this embodiment, the isolation transformer T 1 The reference winding Ref is 20 turns, the winding W at the input end is 50 turns; the winding W at the first output end is 1 The winding W of the second output terminal is 100 turns. 2 For 100 turns.

[0088] The test results of measuring the amplification factor and phase shift of the voltage amplifier using the device and method of the present invention are shown in Table 1:

[0089]

[0090] Table 1

[0091] In Table 1, the first row shows the nominal value of the voltage amplifier to be measured, and the following are the amplification factors A obtained by using the device and method of the present invention at different measurement frequencies (power supply frequency, circuit operating frequency). V and phase shift.

[0092] Moreover, the present invention solves the traceability problem of the amplification factor and phase shift of the voltage amplifier circuit, because the present invention adopts an inductive shunt to provide two equal working currents, which can be traced back to the proportional standard, and the amplification factor and phase shift are calculated by the sampling method. The voltage sampling method can be traced back to the AC voltage standard, so the method of the present invention has traceability. Through uncertainty assessment, the uncertainty of the amplification factor obtained by the present invention is 0.02% (k = 2), and the uncertainty of the phase shift is 0.004° (k = 2), where k is the inclusion factor used in the uncertainty assessment. From these two uncertainties, it can be seen that the accuracy of the amplification factor and phase shift obtained by the present invention is very high.

[0093] In practical applications, the present invention can be used to calibrate the gain and phase shift of the voltage amplifier on the one hand, and on the other hand, the voltage amplifier with calibrated gain and phase shift can be brought into other application circuits to correct or compensate the measurement results. For example, the impedance value corresponding to a large capacitor is small, and the working voltage at both ends is small, which may be as small as 1mV. When the voltage is less than 10mV, direct sampling with a sampling voltmeter has very low accuracy. The sampling voltage of the digital multimeter 3458 must be greater than 0.1V, so the voltage at both ends of the capacitor is first amplified by a voltage amplifier, and then sampled and measured with a digital meter. Therefore, it is necessary to first use the device and method of the present invention to measure the amplitude and phase shift of the voltage amplifier, and then connect the voltage amplifier to the following circuits: Figure 3 In the circuit shown, the measurement of large capacitance is realized.

[0094] The voltage amplifier whose amplitude and phase shift are measured by the present invention can also be used for accurate measurement of a phase lead or lag circuit composed of an operational amplifier, or for simulating a loss standard (the real part of the capacitor corresponds to loss, and the imaginary part corresponds to capacitance) to achieve arbitrary transformation of amplitude and phase angle, or for measuring the real and imaginary parts of impedance.

[0095] The above technical solution is only one implementation mode of the present invention. For those skilled in the art, it is easy to make various types of improvements or modifications based on the application methods and principles disclosed in the present invention, and it is not limited to the method described in the above specific implementation mode of the present invention. Therefore, the method described above is only preferred and does not have a restrictive meaning.

Claims

1. A device for measuring the amplification factor and phase shift of a voltage amplifier, characterized in that: The device for measuring the amplification factor and phase shift of the voltage amplifier comprises: an isolation transformer, an inductive shunt, a comparison circuit, a measurement circuit, a sampling unit, a calculation unit and a power supply; The isolation transformer comprises an input end and two output ends; the input end is connected to the power supply; the two output ends are respectively connected in series in the comparison circuit and the measurement circuit; The inductive shunt comprises a first winding and a second winding; the first winding has a head end connected to a current input end of the comparison loop, and a tail end connected to a current output end of the comparison loop; the second winding has a head end connected to a current output end of the measurement loop, and a tail end connected to a current input end of the measurement loop; The sampling unit is connected to the comparison circuit, the measurement circuit, and the calculation unit respectively; The comparison circuit comprises a second standard resistor R2′ for the comparison circuit, a first standard resistor R1 for the comparison circuit, a first winding of the inductive shunt, and a first output end of the isolation transformer, which are connected in series in sequence, and the four are connected to form a circuit; The measuring circuit comprises a first standard resistor R1′ for the measuring circuit, a second standard resistor R2 for the measuring circuit, a second winding of the inductive shunt, and a second output end of the isolation transformer, which are connected in series in sequence, and the four are connected to form a circuit; The two ends of the voltage amplifier to be measured are respectively connected to the two voltage measuring ends of the second standard resistor R2 of the measurement loop.

2. The device for measuring the amplification factor and phase shift of a voltage amplifier according to claim 1, characterized in that: The turns ratio of the first winding to the second winding is 1:

1.

3. The device for measuring the amplification factor and phase shift of a voltage amplifier according to claim 1, characterized in that: The sampling unit includes a first sampling voltmeter and a second sampling voltmeter; The two ends of the first sampling voltmeter are respectively connected to the two voltage measuring ends of the first standard resistor R1 for the comparison loop; Two ends of the second sampling voltmeter are respectively connected to two voltage measuring ends of the voltage amplifier to be measured.

4. The device for measuring the amplification factor and phase shift of a voltage amplifier according to claim 3, characterized in that: The sampling unit further includes a sampling trigger; The sampling trigger is connected to the external triggering end of the first sampling voltmeter and the second sampling voltmeter respectively; The calculation unit is connected to the sampling trigger, the first sampling voltmeter, and the second sampling voltmeter respectively.

5. The device for measuring the amplification factor and phase shift of a voltage amplifier according to claim 4, characterized in that: The first standard resistor R1 used in the comparison circuit has the same resistance value as the first standard resistor R1′ used in the measurement circuit; The second standard resistor R2′ used in the comparison circuit has the same resistance value as the second standard resistor R2 used in the measurement circuit; The first standard resistor R1 used in the comparison circuit is K times the resistance value of the second standard resistor R2 used in the measurement circuit; The K is equal to the nominal value of the voltage amplifier to be tested.

6. The device for measuring the amplification factor and phase shift of a voltage amplifier according to claim 5, characterized in that: The device includes a lock-in amplifier; The lock-in amplifier comprises a Lock-in terminal, an A terminal and a B terminal; The Lock-in terminal of the lock-in amplifier is connected to the reference winding Ref of the isolation transformer; The A terminal of the lock-in amplifier is connected to the first winding of the inductive shunt; The B terminal of the lock-in amplifier is connected to the second winding of the inductive shunt.

7. A method for measuring the amplification factor and phase shift of a voltage amplifier, characterized in that: The method comprises: (1) Connect the input end of the isolation transformer to the power supply; (2) constructing a comparison loop: connecting the second standard resistor R2′ for the comparison loop, the first standard resistor R1 for the comparison loop, the first winding of the inductive shunt, and the first output end of the isolation transformer in series to form a comparison loop; wherein the head end of the first winding of the inductive shunt is connected to the current input end of the comparison loop, and the tail end of the first winding is connected to the current output end of the comparison loop; (3) constructing a measurement loop: connecting the first standard resistor R1′ for the measurement loop, the second standard resistor R2 for the measurement loop, the second winding of the inductive shunt, and the second output end of the isolation transformer in series to form a measurement loop; wherein the head end of the second winding of the inductive shunt is connected to the current output end of the measurement loop, and the tail end of the second winding is connected to the current input end of the measurement loop; (4) Connecting the voltage amplifier to be tested: Connecting the two ends of the voltage amplifier to be tested to the two voltage measuring ends of the second standard resistor R2 in the measuring loop respectively; (5) Connecting the sampling unit: Connecting the two ends of the first sampling voltmeter to the two voltage measuring ends of the first standard resistor R1 used in the comparison circuit; connecting the two ends of the second sampling voltmeter to the two voltage measuring ends of the voltage amplifier to be measured; (6) Connecting a sampling trigger and a computing unit: connecting the sampling trigger to the external trigger terminals of the first sampling voltmeter and the second sampling voltmeter respectively; connecting the computing unit to the sampling trigger, the first sampling voltmeter, and the second sampling voltmeter respectively; (7) Synchronous sampling to obtain voltage value: synchronously sampling the first sampling voltmeter and the second sampling voltmeter to obtain the voltage value on the first sampling voltmeter The voltage value on the second sampling voltmeter (8) Calculate the amplification factor A of the voltage amplifier to be tested v And phase shift: using the voltage value on the first sampling voltmeter The voltage value on the second sampling voltmeter Get the amplification factor A of the voltage amplifier to be tested v and phase shift.

8. The method according to claim 7, characterized in that: The operation of step (8) includes: using the following formula to calculate the amplification factor A of the voltage amplifier to be tested: v and phase shift Among them, b1 and a1 are The sine and cosine amplitudes, b2 and a2 are The sine and cosine amplitudes.

9. The method according to claim 7, characterized in that: There is also an impedance adjustment step between step (6) and step (7), comprising: (S1) connecting the Lock-in terminal of the lock-in amplifier to the reference winding Ref of the isolation transformer, connecting the A terminal of the lock-in amplifier to the first winding of the inductive shunt, and connecting the B terminal of the lock-in amplifier to the second winding of the inductive shunt; (S2) setting the lock-in amplifier to AB function; (S3) Observe whether the display value of the phase-locked amplifier is 0. If not, connect a resistor in series or in parallel with the first standard resistor R1′ in the measurement loop, and then return to step (S3). If yes, proceed to step (S4); (S4) Disconnect the Lock-in terminal of the phase-locked amplifier from the reference winding Ref of the isolation transformer, disconnect the A terminal of the phase-locked amplifier from the first winding of the inductive shunt, and disconnect the B terminal of the phase-locked amplifier from the second winding of the inductive shunt.

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