A device for measuring polarization voltage of microphone

Abstract

The present invention discloses a device for measuring polarization voltage of a microphone. In order to solve the problem that the operation of measuring polarization voltage in the prior art is complicated and the accurate value cannot be measured after simplified operation, the device comprises a high-voltage impedance transformation module, a direct current voltmeter, an isolation power supply module and a high-voltage direct current voltage selection module. The extremely high output impedance of the polarization voltage is reduced to an extremely low output impedance through the high-voltage impedance transformation module and then connected to the direct current voltmeter, so that the value of the polarization voltage can be directly measured by using an ordinary direct current voltmeter. The present invention can reduce the difficulty of measuring polarization voltage and the complexity of equipment, improve the measurement accuracy of polarization voltage, and accurately measure the value of polarization voltage.

Description

Technical Field

[0001] The invention relates to the field of metering devices, and in particular to a device for measuring polarization voltage. Background Art

[0002] The measuring amplifier is a wide-range, low-noise instrument with specified time weighting, frequency weighting and voltage indication functions. It is mainly used for engineering measurements in acoustics and vibration, as well as verification and calibration of acoustic and vibration measuring instruments. The measuring amplifier should be able to provide polarization voltage for the microphone. The nominal value of polarization voltage is usually 200V, 28V and 0V. Unlike general voltage signals, polarization voltage has a very high output impedance, usually tens or even hundreds of megohms, and cannot be accurately measured with an ordinary voltmeter. Therefore, in the national metrology technical specifications, an indirect method - compensation method is recommended, that is, the output of the adjustable DC regulated power supply and the output of the measuring amplifier polarization voltage are connected to the two ends of the DC galvanometer respectively, and the output of the DC regulated power supply is also connected to the digital voltmeter. Adjust the output voltage of the adjustable DC regulated power supply to make it close to the nominal value of the polarization voltage, and then carefully adjust the output voltage of the adjustable DC regulated power supply so that the reading of the DC galvanometer is zero. At this time, the indication of the digital voltmeter is the value of the polarization voltage. However, this measurement method requires the use of three instruments, is relatively complicated, and has high requirements on operators. Although the simplified device for detecting polarization voltage in the prior art can complete the detection of polarization voltage with only one device, it cannot accurately measure the value of polarization voltage.

[0003] For example, a "polarization voltage measuring device for a satellite set-top box" disclosed in a Chinese patent document, with a publication number of "CN211293042U", includes a polarization voltage constant circuit, a polarization voltage access switch and a control delay circuit. The input end of the polarization voltage constant circuit is connected to a polarization voltage test interface, and the output end of the polarization voltage constant circuit is respectively connected to two voltage comparison circuits and a polarization voltage access switch. The two voltage comparison circuits are respectively connected to two independent control delay circuits. The polarization voltage access switch is also respectively connected to the two control delay circuits through relays. The two control delay circuits are respectively connected to speakers and indicator lights through independent relays. Although the number of operators and the complexity of operation can be reduced, the detection effect is also reduced at the same time. Only the existence of polarization voltage can be detected, but the accurate value of the polarization voltage cannot be measured. Summary of the invention

[0004] In order to solve the problem in the prior art that the operation of measuring polarization voltage is complicated and accurate values ​​cannot be measured after simplified operation, the present invention provides a device for measuring polarization voltage of a microphone.

[0005] A device for measuring microphone polarization voltage of the present invention comprises:

[0006] High-voltage impedance conversion module: used to receive polarization voltage signals, increase the input impedance of the circuit and reduce the output impedance, and output the signal to the DC voltmeter;

[0007] DC voltmeter: used to measure the voltage signal output by the high-voltage impedance conversion module;

[0008] Isolated power supply module: used to provide ground-isolated positive and negative power supplies for the high-voltage impedance conversion module. The core component of the high-voltage impedance conversion circuit is an ordinary JFET-Input op amp, which is powered by dual power supplies. JFET-Input is selected because this op amp has a very high input impedance, which can reach more than 100GΩ. The input impedance of the circuit is increased by the high-voltage impedance conversion module, and the input impedance of the circuit can be regarded as infinite, eliminating the influence of the high output impedance of the polarization voltage. The isolated power supply provides a higher ground voltage for the op amp of the high-voltage impedance module, so that the op amp can meet the polarization voltage requirement of up to 200V, and the polarization voltage can be accurately measured directly using an ordinary DC voltmeter.

[0009] Preferably, a high-voltage DC voltage selection module is also included, which is used to output different reference voltages to the isolated power supply module.

[0010] Preferably, the high-voltage impedance conversion module includes an operational amplifier, the positive input terminal of the operational amplifier is the input terminal of the polarization voltage, the output terminal of the operational amplifier is connected to the negative input terminal, and the output terminal of the operational amplifier is connected to the input terminal of the DC voltmeter. The output of the operational amplifier is connected to the negative input terminal to form a voltage follower circuit, which further increases the input impedance of the operational amplifier circuit. The voltage follower circuit also has an extremely low output impedance, and the output terminal can be connected to an ordinary DC voltmeter, so that the circuit structure is simple and the component cost is low.

[0011] Preferably, the positive and negative output terminals of the isolation power module are electrically connected to the positive and negative power input terminals of the operational amplifier, and the 0V output terminal of the isolation power module is electrically connected to the capacitor of the power input terminal of the operational amplifier. The reference voltage VREF output by the high-voltage DC voltage selection module 3 is connected to the 0V output terminal of the isolation power module to increase the ground voltage of the output terminal of the isolation power module, which can correspondingly increase the operating voltage of the operational amplifier without changing the voltage difference between the positive and negative power terminals of the operational amplifier.

[0012] Preferably, the high-voltage DC voltage selection module includes a high-voltage DC voltage unit and a voltage selection unit, the high-voltage DC voltage unit is used to output high-voltage DC power to the voltage selection unit, and the voltage selection unit is used to divide the voltage output by the high-voltage DC voltage unit into several gears and output it to the 0V output end of the isolation power supply module.

[0013] Preferably, the voltage selection unit comprises a voltage divider network composed of at least two resistors connected end to end, and the output end of the voltage divider network is connected to the 0V output end of the isolation power supply module through a single-pole multi-throw switch. Through the voltage divider network composed of resistors, the high-voltage DC voltage selection module can output different voltages to adapt to different polarization voltage values.

[0014] Preferably, the high voltage DC voltage selection module comprises:

[0015] MCU unit: used to monitor the output voltage of the high-voltage impedance conversion module and output control signals to the voltage selection unit;

[0016] High-voltage DC voltage unit: outputs high-voltage DC voltage to the voltage selection module;

[0017] Voltage selection unit: receives the control signal of the MCU unit to switch different voltage outputs to the isolated power module.

[0018] Preferably, the voltage selection unit is provided with a relay, a control end of the relay is connected to the output end of the MCU unit for selecting different voltage outputs.

[0019] Preferably, the MCU unit is connected to an LED light for indicating the working status of the circuit.

[0020] Beneficial effects: 1. It can reduce the operational difficulty and equipment complexity of measuring polarization voltage;

[0021] 2. Improve the measurement accuracy of polarization voltage and accurately measure the value of polarization voltage;

[0022] 3. Automatically measure the actual value of polarization voltage and further simplify the measurement operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the connection structure between a high-voltage impedance conversion circuit module and a DC voltmeter of a device for measuring microphone polarization voltage of the present invention;

[0024] Figure 2 It is a schematic diagram of the connection relationship between an isolation power supply module and a high-voltage direct current voltage selection module of a device for measuring the polarization voltage of a microphone according to the present invention;

[0025] Figure 3 It is a circuit principle schematic diagram of a second embodiment of a device for measuring polarization voltage of a microphone according to the present invention;

[0026] In the figure, 1. high voltage impedance transformation module; 2. isolation power supply module; 3. high voltage DC voltage selection module; 31. high voltage DC voltage unit; 32. MCU unit. DETAILED DESCRIPTION

[0027] Embodiment 1: Figure 1~2 As shown, a device for measuring microphone polarization voltage includes a high-voltage impedance transformation module 1, a DC voltmeter, an isolation power supply module 2, and a high-voltage DC voltage selection module 3.

[0028] The high-voltage impedance conversion module 1 is used to receive the polarization voltage signal, increase the input impedance of the circuit and reduce the output impedance, and output the signal to the DC voltmeter; the high-voltage impedance conversion module 1 includes an operational amplifier U2, the positive input end of the operational amplifier U2 is the input end of the polarization voltage, the output end of the operational amplifier U2 is connected to the negative input end, and the output end of the operational amplifier U2 is connected to the input end of the DC voltmeter. The output of the operational amplifier U2 is connected to the negative input end to form a voltage follower circuit, which further increases the input impedance of the operational amplifier circuit. The voltage follower circuit also has an extremely low output impedance, and the output end can be connected to an ordinary DC voltmeter, making the circuit structure simple and the component cost low. The core component of the high-voltage impedance conversion circuit is an ordinary JFET-Input operational amplifier, which is powered by dual power supplies. JFET-Input is selected because this operational amplifier has a very high input impedance, which can reach more than 100GΩ. The input impedance of the circuit is increased by the high-voltage impedance conversion module 1, and the input impedance of the circuit can be regarded as infinite, eliminating the influence of the high output impedance of the polarization voltage.

[0029] The DC voltmeter is used to measure the voltage signal output by the high-voltage impedance transformation module 1 .

[0030] The isolated power supply module 2 is used to provide the positive and negative power supplies isolated from the ground for the high-voltage impedance transformation module 1. The positive and negative power supply output terminals of the isolated power supply module 2 are connected to the power supply input terminal of the operational amplifier U2, and the 0V output terminal of the isolated power supply module 2 is electrically connected to the power supply input terminal of the operational amplifier U2 through capacitors C2 and C3. The reference voltage VREF output by the high-voltage DC voltage selection module 3 is connected to the 0V output terminal of the isolated power supply module 2 to increase the voltage to the ground of the output terminal of the isolated power supply module, which can correspondingly increase the operating voltage of the operational amplifier without changing the voltage difference between the positive and negative power supply terminals of the operational amplifier, so that the operational amplifier can input a polarization voltage of up to 200V, and the polarization voltage can be directly and accurately measured using an ordinary DC voltmeter.

[0031] The high-voltage direct current voltage selection module 3 is used to output different voltages to the isolated power supply module 2. The high-voltage direct current voltage selection module 3 includes a high-voltage direct current voltage unit 31 and a voltage selection unit. The high-voltage direct current voltage unit 31 is used to output high-voltage direct current to the voltage selection unit. The voltage selection unit is used to divide the voltage output by the high-voltage direct current voltage unit 31 into several gears and output them to the 0V output end of the isolated power supply module 2. The voltage selection unit includes a voltage-dividing network composed of at least two resistors connected end to end, and the output end of the voltage-dividing network is connected to the 0V output end of the isolated power supply module 2 through a single-pole multi-throw switch. The nominal value of the polarization voltage is usually 200V, 28V and 0V. In addition, the nominal value of the polarization voltage of some instruments is 60V. In this embodiment, three voltage-dividing resistors are used to divide the voltage into four gears corresponding to four different nominal values ​​of the polarization voltage. Through the voltage-dividing network composed of resistors, the high-voltage direct current voltage selection module 3 can output different voltages and adapt to different polarization voltage values.

[0032] An electromagnetic attractor is also provided at the position where the voltage of the voltage-dividing network is the largest, and the electromagnetic attractor is used to switch the switch to the maximum voltage position when the measuring device turns off the power supply. After a measurement operation is completed, if the operator turns off the power supply of the measuring device, the measuring device will energize the electromagnetic attractor before completely turning off the power supply, so that the electromagnetic attractor closes the switch and switches the position to the maximum output voltage position of the high-voltage DC voltage unit, and finally completely cuts off the power supply to avoid the operator's mistake of measuring a larger polarization voltage with a small voltage position during the next use, causing damage to the device. In this embodiment, an electromagnetic attractor is connected to the other end where the resistor R14 is connected to the resistor R15. The electromagnetic attractor can be a device that can generate magnetism after being energized, such as an electromagnetic solenoid, and the single-pole multi-throw switch should also be made of a material that can be attracted by a magnet and has good conductivity.

[0033] During actual measurement, the polarization voltage is input from the SIN terminal, and a suitable reference voltage VREF is selected according to the nominal value of the polarization voltage. The single-pole multi-throw switch is turned to the corresponding position to provide a larger reference voltage for the operational amplifier U2 so that the operational amplifier can adapt to the polarization voltage. The high-voltage impedance transformation module 1 reduces the output impedance to an extremely low level, and an ordinary DC voltmeter can be used to measure the accurate actual voltage value of the polarization voltage.

[0034] Embodiment 2: Figure 3As shown, in order to cope with the situation of different polarization voltage values ​​in actual use and realize the function of automatically switching the reference voltage value VREF, the following improvements are made relative to the first embodiment: the output end of the high-voltage DC voltage module 3 is connected to a resistor voltage-dividing network, and multiple voltage reference values ​​can be generated by matching the resistance values. In this embodiment, the output end of the high-voltage DC voltage unit 31 is connected to three resistors connected end to end, the output end of the MCU is connected to the control end of two relays, and the wiring terminals of the relays correspond to the wiring terminals of the resistor voltage-dividing network with different voltage values. The output of the operational amplifier U2 is divided by two resistors R17 and R18, and then connected to the ADC input pin of the MCU. The MCU unit 32 monitors the level of the input signal, and then controls the switching of relays K2 and K3 according to the value of the input signal level, and selects the corresponding voltage value as VREF. The MCU unit 32 controls a green LED and a red LED, and lights the green LED when working normally, and lights the red LED when abnormal. The other module designs of this embodiment are the same as those of the first embodiment.

[0035] Working principle: In the default state, the 2nd and 3rd pins of relays K2 and K3 are turned on, and the reference voltage VREF is connected to 28V; if the voltage VS value collected by the ADC at the input end of the MCU is also around 28V, the relay will not switch and the green LED will be lit; if VS - VREF > 5, it means that the external polarization voltage value exceeds 28V, at this time, the MCU controls the 1st and 3rd pins of relay K2 to be turned on, the 2nd and 3rd pins of K3 to be turned on, and VREF is connected to 60V. At this time, if the voltage value VS collected by the MCU is also about 60V, the relay does not switch and the green LED is lit; if VS - VREF > 5, it means that the external polarization voltage value exceeds 60V. At this time, the MCU controls the 1 and 3 pins of the relay K3 to be turned on, and VREF is connected to 200V; again, if the voltage value VS collected by the MCU unit 32 is also about 200V, the relay does not switch and the green LED is lit; if VS - VREF > 5, it means that the external polarization voltage value exceeds 200V. At this time, the MCU lights up the red LED to indicate an abnormality.

Claims

1. A device for measuring microphone polarization voltage, characterized in that: include: The high-voltage impedance conversion module includes an operational amplifier, which is used to receive polarization voltage signals, increase the input impedance of the circuit and reduce the output impedance, and output the signal to a DC voltmeter; A DC voltmeter, used to measure the voltage signal output by the high-voltage impedance conversion module; An isolated power supply module, used to provide ground-isolated positive and negative power supplies for the operational amplifier of the high-voltage impedance conversion module, wherein a 0V output reference terminal of the isolated power supply module is connected to a reference voltage VREF and is also electrically connected to a capacitor at a power input terminal of the operational amplifier; The high-voltage DC voltage selection module is used to output different reference voltages VREF to the isolated power supply module.

2. The device for measuring microphone polarization voltage according to claim 1, characterized in that: The high-voltage impedance conversion module includes an operational amplifier, a positive input terminal of the operational amplifier is an input terminal of a polarization voltage, an output terminal of the operational amplifier is connected to a negative input terminal, and an output terminal of the operational amplifier is connected to an input terminal of a DC voltmeter.

3. The device for measuring microphone polarization voltage according to claim 2, characterized in that: The positive and negative output terminals of the isolated power supply module are electrically connected to the positive and negative power supply input terminals of the operational amplifier.

4. The device for measuring microphone polarization voltage according to claim 1, characterized in that: The high-voltage DC voltage selection module includes a high-voltage DC voltage unit and a voltage selection unit. The high-voltage DC voltage unit is used to output high-voltage DC power to the voltage selection unit, and the voltage selection unit is used to divide the voltage output by the high-voltage DC voltage unit into several gears and output it to the 0V output end of the isolation power supply module.

5. The device for measuring microphone polarization voltage according to claim 4, characterized in that: The voltage selection unit comprises a voltage divider network consisting of at least two resistors connected end to end, and the output end of the voltage divider network is connected to the 0V output end of the isolation power supply module through a single-pole multi-throw switch.

6. The device for measuring microphone polarization voltage according to claim 1, characterized in that: The high voltage DC voltage selection module comprises: MCU unit: used to monitor the output voltage of the high-voltage impedance conversion module and output a control signal to the voltage selection unit; High-voltage DC voltage unit: outputs a high-voltage DC voltage to the voltage selection module; Voltage selection unit: receives the control signal of the MCU unit to switch different voltage outputs to the isolated power module.

7. The device for measuring microphone polarization voltage according to claim 6, characterized in that: The voltage selection unit is provided with a relay, and a control end of the relay is connected to the output end of the MCU unit for selecting different voltage outputs.

8. The device for measuring microphone polarization voltage according to claim 6, characterized in that: The MCU unit is connected to an LED light to indicate the working status of the circuit.

Images