Non-contact dc voltage measuring device with oscillating sensor

Abstract

The present invention relates to a non-contact DC voltage measurement device with an oscillating sensor. Systems and methods are provided for measuring the direct current (DC) voltage of an insulated conductor (e.g., an insulated wire) without requiring an electrical connection between the conductor and a test electrode or probe. A non-contact DC voltage measurement device can include a conductive sensor that is mechanically oscillated. The insulated conductor to be measured serves as a first conductive element or electrode of a coupling capacitor, and the vibrating conductive sensor serves as a second conductive element or electrode of the coupling capacitor. The oscillation of the conductive sensor provides a time-varying capacitance value for the coupling capacitor. The measurement device detects the current flowing through the coupling capacitor and uses the detected current and the time-varying capacitance to determine the DC voltage in the insulated conductor. The determined DC voltage can be output to a display or transmitted to an external system via a wired or wireless connection.

Description

[0001] This application is a divisional application. The parent application is entitled "Non-contact DC voltage measuring device with oscillation sensor", filed on May 10, 2019, with application number 201910389076.0. Technical Field

[0002] This disclosure relates generally to the measurement of electrical characteristics, and more specifically, to the non-contact measurement of direct current (DC) voltage. Background Technology

[0003] A voltmeter is an instrument used to measure voltage in a circuit. An instrument that measures more than one electrical characteristic is called a multimeter or digital multimeter (DMM) and is used to measure many parameters typically required for service, troubleshooting, and maintenance applications. These parameters typically include alternating current (AC) voltage and current, direct current (DC) voltage and current, and resistance or continuity. Other parameters, such as power characteristics, frequency, capacitance, and temperature, can also be measured to meet the requirements of specific applications.

[0004] For conventional voltmeters or multimeters used to measure DC voltage, at least one measuring electrode or probe needs to be in electrical contact with a conductor. This typically requires cutting a portion of the insulation from the insulated wire or providing a measuring terminal beforehand. In addition to requiring exposed wire or terminal for electrical contact, the step of touching the voltmeter probe to a stripped wire or terminal can be quite dangerous due to the risk of electric shock.

[0005] Therefore, there is a need for a DC voltage measuring device that provides convenient and accurate voltage measurement without requiring electrical contact with the circuit under test. Summary of the Invention

[0006] An apparatus for measuring a direct current (AC) voltage in an insulated conductor can be summarized as comprising: a housing; a conductive sensor physically coupled to the housing, the conductive sensor being selectively positioned close to the insulated conductor without electrical contact with the insulated conductor, wherein the conductive sensor is capacitively coupled to the insulated conductor; a conductive internal grounding protection element at least partially surrounding and electrically isolating the conductive sensor, the size and dimensions of the internal grounding protection element being designed to protect the conductive sensor from stray currents; a conductive reference shield surrounding at least a portion of the housing and electrically insulated from the internal grounding protection element, the size and dimensions of the conductive reference shield being designed to reduce the current between the internal grounding protection element and an external ground terminal; and a mechanical oscillator operatively coupled to the conductive sensor, wherein, in operation, the mechanical oscillator causes the conductive sensor to... Mechanical oscillation is performed based on the mechanical oscillation amplitude and frequency, such that the distance between the conductive sensor and the insulating conductor varies periodically according to the mechanical oscillation amplitude and frequency; a common-mode reference voltage source generates an alternating current (AC) reference voltage with a reference frequency during operation, electrically coupled between an internal grounding protection element and a conductive reference shield; a sensor signal measurement subsystem electrically coupled to the conductive sensor, wherein the sensor signal measurement subsystem generates a sensor current signal indicating the current conducted through the conductive sensor during operation; and a control circuit communicatively coupled to the sensor signal measurement subsystem, wherein during operation, the control circuit: receives the sensor current signal from the sensor signal measurement subsystem; and determines the DC voltage in the insulating conductor based at least in part on the received sensor current signal. The control circuit may determine the DC voltage in the insulating conductor based at least in part on the received sensor current signal, the mechanical oscillation frequency, the AC reference voltage, and the reference frequency. The mechanical oscillator may include a piezoelectric mechanical oscillator. The mechanical oscillator may include a microelectromechanical (MEMS) mechanical oscillator.

[0007] The control circuitry, in operation, converts the received sensor current signal into a digital signal and processes the digital signal to obtain a frequency domain representation of the sensor current signal. The control circuitry may implement a Fast Fourier Transform (FFT) to obtain the frequency domain representation of the sensor current signal. A common-mode reference voltage source may generate an AC reference voltage in phase with the window of the FFT implemented by the control circuitry. The control circuitry may include at least one electronic filter to filter the received sensor current signal. The control circuitry may process the sensor current signal to determine an insulating conductor current component and a reference current component, the insulating conductor current component indicating the current conducted through the conductive sensor due to the voltage in the insulating conductor, and the reference current component indicating the current conducted through the conductive sensor due to the voltage of the common-mode reference voltage source. The control circuitry may determine the frequency of the determined insulating conductor current component of the sensor current signal. In operation, the sensor signal measurement subsystem may receive an input current from the conductive sensor, and the sensor current signal may include a voltage signal indicating the input current received from the conductive sensor. The sensor signal measurement subsystem may include an operational amplifier operating as a current-to-voltage converter.

[0008] A method for operating an apparatus to measure a direct current (DC) voltage in an insulated conductor, the apparatus comprising: a housing; a conductive sensor physically coupled to the housing, the conductive sensor being selectively positioned near the insulated conductor without electrical contact with the conductor; a conductive internal grounding protection element at least partially surrounding and electrically isolated from the conductive sensor, wherein the size and dimensions of the internal grounding protection element are designed to protect the conductive sensor from stray currents; and a conductive reference shield surrounding at least a portion of the housing and electrically insulated from the internal grounding protection element, wherein the size and dimensions of the conductive reference shield are designed to reduce the current between the internal grounding protection element and an external ground terminal, the method being generalizable. The method includes: mechanically oscillating a conductive sensor according to the mechanical oscillation amplitude and frequency, such that the distance between the conductive sensor and the insulating conductor changes periodically according to the mechanical oscillation amplitude and frequency; generating an AC reference voltage source with a reference frequency, the common-mode reference voltage source being electrically coupled between an internal grounding protection element and a conductive reference shield; generating a sensor current signal indicating the current conducted through the conductive sensor by a sensor signal measurement subsystem; receiving the sensor current signal from the sensor signal measurement subsystem by a control circuit; and determining the DC voltage in the insulating conductor by the control circuit based at least in part on the received sensor current signal.

[0009] Generating a sensor current signal may include receiving an input current from a conductive sensor and generating a voltage signal indicating the input current received from the conductive sensor. This sensor current signal may be generated using an operational amplifier operating as a current-to-voltage converter. Mechanically oscillating the conductive sensor may include using a piezoelectric mechanical oscillator to mechanically oscillate the conductive sensor. Mechanically oscillating the conductive sensor may also include using a microelectromechanical (MEMS) mechanical oscillator to mechanically oscillate the conductive sensor.

[0010] Determining the DC voltage in an insulated conductor may include converting a received sensor current signal into a digital signal by at least one processor; and processing the digital signal by at least one processor to obtain a frequency domain representation of the sensor current signal. Processing the digital signal may include implementing a Fast Fourier Transform (FFT) to obtain a frequency domain representation of the sensor current signal. Determining the DC voltage in an insulated conductor may also include electronically filtering the received sensor current signal.

[0011] An apparatus for measuring a direct current (DC) voltage in an insulated conductor can be summarized as comprising: a conductive sensor capable of selectively positioning close to the insulated conductor without electrical contact with it, wherein the conductive sensor is capacitively coupled to the insulated conductor; a mechanical oscillator operably coupled to the conductive sensor, wherein in operation the mechanical oscillator causes the conductive sensor to mechanically oscillate to change the capacitance between the conductive sensor and the insulated conductor relative to time; a conductive internal grounding protection member at least partially surrounding and electrically isolated from the conductive sensor; and a conductive reference shield surrounding at least a portion of a housing and electrically insulated from the internal grounding protection member; in operation A common-mode reference voltage source generating an alternating current (AC) reference voltage with a reference frequency, electrically coupled between an internal grounding protection element and a conductive reference shield; a sensor signal measurement subsystem electrically coupled to a conductive sensor, wherein the sensor signal measurement subsystem generates a sensor current signal indicating the current conducted through the conductive sensor during operation; and control circuitry communicatively coupled to the sensor signal measurement subsystem, wherein during operation, the control circuitry: receives the sensor current signal from the sensor signal measurement subsystem; and determines a DC voltage in an insulating conductor based at least in part on the received sensor current signal. During operation, the control circuitry may determine the DC voltage in the insulating conductor based on the received sensor current signal and on the capacitance change between the conductive sensor and the insulating conductor relative to time. The mechanical oscillator may include at least one of a piezoelectric mechanical oscillator or a microelectromechanical (MEMS) mechanical oscillator. Attached Figure Description

[0012] In the accompanying drawings, the same reference numerals indicate similar elements or actions. The size and relative positions of the elements in the drawings are not necessarily drawn to scale. For example, the shapes and angles of various elements are not necessarily drawn to scale, and some of these elements may be arbitrarily enlarged and positioned to improve the readability of the drawings. Furthermore, the specific shapes of the drawn elements are not necessarily intended to convey any information about the actual shape of the particular element and may be chosen solely for ease of identification in the drawings.

[0013] Figure 1A This is a schematic diagram based on an illustrative specific implementation environment in which an operator can use a non-contact DC voltage measuring device to measure the DC voltage present in an insulated wire without needing to make electrical contact with the wire.

[0014] Figure 1B It is based on a specific implementation of an example. Figure 1A A top view of a non-contact DC voltage measuring device, showing the coupling capacitance formed between the insulated wire and the conductive sensor of the non-contact voltage measuring device.

[0015] Figure 2 This is a schematic diagram of the various internal components of a non-contact DC voltage measuring device according to an exemplary embodiment.

[0016] Figure 3 This is a block diagram illustrating various signal processing components of a non-contact DC voltage measuring device according to an exemplary implementation.

[0017] Figure 4 This is a block diagram of a non-contact DC voltage measurement device that implements an analog electronic filter based on an example of signal and reference signal separation. Detailed Implementation

[0018] One or more specific embodiments of this disclosure relate to systems and methods for measuring DC voltage in insulated conductors or uninsulated bare conductors (e.g., insulated wires) without requiring an electrical connection between the conductor and a test electrode or probe. Generally, non-contact (or “non-contact”) voltage measuring devices are provided that use a vibrating capacitance sensor to measure a DC voltage signal in an insulated conductor relative to a ground terminal. Such devices that do not require an electrical connection are referred to herein as “non-contact.” As used herein, “electrical coupling” includes both direct and indirect electrical coupling unless otherwise stated.

[0019] As an overview, a non-contact DC voltage measurement device may include a non-contact conductive sensor (e.g., a conductive film) that mechanically oscillates or vibrates using a suitable oscillator (e.g., a piezoelectric oscillator, a micromechanical system (MEMS) oscillator). The conductive sensor may be positioned close to the insulating conductor under test, for example, within a few millimeters of the conductor. To obtain a measurement, the insulating conductor under test serves as a first conductive element or electrode of a coupling capacitor, and the vibrating conductive sensor serves as a second conductive element or electrode of the coupling capacitor. The capacitance of the resulting coupling capacitor varies with time due to the vibration of the sensor, as the vibration causes the distance between the sensor and the conductor under test to become variable. This non-contact DC voltage measurement device includes a means for detecting or measuring the AC current flowing through the coupling capacitor due to vibration, referred to herein as the signal current (I0). O The AC signal current is proportional to the time-varying change in the DC voltage across the coupling capacitor and the capacitance of the coupling capacitor caused by vibration of the non-contact conductive sensor. This DC voltage measuring device uses a known reference voltage that generates a reference current and the AC voltage of the vibrating non-contact sensor (e.g., 0 volts or ground) to determine the DC voltage across the coupling capacitor using the detected signal current generated by the vibration.

[0020] The determined DC voltage in the insulated conductor can be output to the user (e.g., via a display) or transmitted to an external system via one or more wired or wireless connections. In addition to DC voltage, the measuring device discussed herein may also include functions for determining other electrical parameters, such as, but not limited to, AC voltage, AC current or DC current, power, phase angle, waveform, thermal characteristics, impedance, etc.

[0021] In the following description, certain specific details are set forth in order to provide a thorough understanding of the various specific embodiments disclosed. However, those skilled in the art will recognize that these embodiments can be implemented without one or more of these specific details, or using other methods, components, materials, etc. In other instances, well-known structures associated with computer systems, server computers, and / or communication networks have not been shown or described in detail to avoid unnecessarily obscuring the description of these embodiments.

[0022] Unless the context otherwise requires, throughout the specification and claims, the word “comprising” is synonymous with “including” and is inclusive or open-ended (i.e., does not exclude additional unreferenced elements or method actions).

[0023] Throughout this specification, references to "an embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment. Therefore, the phrases "in an embodiment" or "in an embodiment" appearing in various places throughout this specification do not necessarily all refer to the same embodiment. Furthermore, in one or more embodiments, a particular feature, structure, or characteristic can be combined in any suitable manner.

[0024] As used in this specification and the appended claims, the singular forms “a” and “the” include plural indicators unless the context clearly indicates otherwise. It should also be noted that the term “or” is generally used to include “and / or” in its sense unless the context clearly indicates otherwise.

[0025] The titles and abstracts provided herein are for convenience only and do not explain the scope or meaning of any particular implementation.

[0026] Figure 1A This is a schematic diagram of environment 100, in which an operator 104 can use the non-contact DC voltage measuring device 102 of this disclosure to measure the DC voltage present in the insulated wire 106 without requiring electrical contact between the non-contact voltage measuring device and the wire 106. Figure 1B yes Figure 1A This is a top view of a non-contact voltage measuring device 102, illustrating various electrical characteristics of the non-contact DC voltage measuring device during operation. The non-contact voltage measuring device 102 includes a housing or body 108, which includes a grip portion or end 110 and a probe portion or end 112 (also referred to herein as a front end) opposite the grip portion. The housing 108 may also include a user interface 114 facilitating user interaction with the non-contact voltage measuring device 102. The user interface 114 may include any number of input elements (e.g., buttons, dials, switches, touch sensors) and any number of output elements (e.g., displays, LEDs, speakers, buzzers). The non-contact voltage measuring device 102 may also include one or more wired and / or wireless communication interfaces (e.g., USB, Wi-Fi). ® Bluetooth ® ), as well as various control or processing circuits (e.g., processors, microcontrollers, DSPs, ASICs, FPGAs, memories).

[0027] In at least some specific implementations, such as Figure 1B As best shown, probe portion 112 may include a recessed portion 116 defined by a first extension 118 and a second extension 120. Recessed portion 116 receives insulated wire 106 (see [reference]). Figure 1AThe insulated wire 106 includes a conductor 122 and an insulator 124 surrounding the conductor 122. When the insulated wire 106 is located within a recess 116 of the non-contact voltage measuring device 102, the recess 116 may include a non-contact conductive sensor or electrode 126 disposed adjacent to the insulator 124 of the insulated wire. The sensor 126 may be positioned inside the housing 108 or in a recessed location to prevent physical and electrical contact between the sensor and other objects. As discussed further below, in operation, the conductive sensor 126 mechanically oscillates during measurement, which allows the measuring device 102 to accurately measure the DC voltage in the insulated conductor 106 under test.

[0028] like Figure 1A As shown, in use, the operator 104 can grasp the grip portion 110 of the housing 108 and position the probe portion 112 close to the insulated wire 106, allowing the non-contact voltage measuring device 102 to accurately measure the DC voltage present in the wire relative to the ground terminal (or another reference node). Although the probe end 112 is shown as having a recessed portion 116, in other embodiments, the probe portion 112 may be configured differently. For example, in at least some embodiments, the probe portion 112 may include a selectively movable clamp, hook, flat or arcuate surface including the sensor, or other types of interfaces that allow the sensor of the non-contact voltage measuring device 102 to be positioned close to the insulated wire 106.

[0029] In some specific implementations, the operator's body may serve as a ground / ground reference. Alternatively, a direct connection via test lead 139 to ground 128 may be used. The non-contact measurement capabilities discussed herein are not limited to applications that measure only relative to ground. An external reference may be capacitively coupled or directly coupled to any other potential. For example, if an external reference is capacitively coupled to another phase in a three-phase system, the phase-to-phase voltage is measured. In general, the concepts discussed herein are not limited to using only body capacitive coupling connected to a reference voltage and any other reference potential for a ground reference.

[0030] As discussed further below, in at least some specific implementations, the non-contact voltage measuring device 102 can utilize the body capacitance (C) between the operator 104 and the grounding terminal 128 during DC voltage measurement. B Although the term "ground terminal" is used for node 128, this node is not necessarily ground / ground terminal, but can be connected to any other reference potential in an electrically isolated manner via capacitive coupling. Measurement device 102 can also be coupled to reference nodes, such as node 128, via conventional electrical coupling (e.g., test leads).

[0031] Figure 2 The same was shown in Figure 1A and Figure 1B The diagram shows a schematic representation of the various internal components of the non-contact voltage measuring device 102. In this example, the conductive sensor 126 of the non-contact voltage measuring device 102 is formed in the form of a plate or film and is positioned close to the insulated wire 106 to be measured, and is capacitively coupled to the conductor 122 of the insulated wire 106, thereby forming a sensor coupling capacitor (C). O It should be understood that the conductive sensor can be other planar shapes (e.g., circular, rectangular, triangular) or non-planar shapes (e.g., V-shaped, U-shaped). The operator 104 operating the non-contact DC voltage measuring device 102 has a capacitance to ground (C). B ).like Figure 1A and Figure 1B As shown, direct conductive grounding coupling via a wire (e.g., test lead 139) can also be used. As discussed further below, this is based on the DC voltage signal (V) in conductor 122. DC ) and the mechanical oscillations caused in sensor 126, in the series-connected coupling capacitor (C O The insulated conductor current component or "signal current" (IC) is generated on the bulk capacitance (CB). O In some specific implementations, the bulk capacitance (C) B It may also include test leads that provide electrical isolation to generate capacitance to ground or any other reference potential.

[0032] DC voltage (V) in wire 122 to be measured DC The non-contact voltage measuring device 102 has a connection to an external ground terminal 128 (e.g., neutral wire). The non-contact voltage measuring device 102 itself also has a capacitance to ground 128, which is primarily composed of the body capacitance (C) when the operator 104 (FIG. 1) holds the non-contact voltage measuring device in their hand. B Composed of: Capacitor C O and C B The two form a conductive loop, and the voltage in this loop generates a signal current (I). O Signal current (I) O The DC voltage signal (V) is capacitively coupled to the conductive sensor 126. DC ) is generated, and through the housing 108 and ground 128 body capacitor (C) of the non-contact DC voltage measuring device. B The loop returns to the external ground terminal 128. Signal current (I) O The voltage level (V) depends on the distance between the conductive sensor 126 of the non-contact voltage measuring device 102 and the insulated wire 106 under test, the specific shape of the conductive sensor 126, and the size of the conductor 122 and the voltage level. DC ).

[0033] To compensate for the direct impact on the signal current (I)O The distance variance and the resulting coupling capacitor (C) O The variance of the non-contact voltage measurement device 102 includes a common-mode reference voltage source 130, which generates a voltage with a frequency (f) consistent with the mechanical oscillation frequency. O Different reference frequencies (f R AC reference voltage (V) R As described below.

[0034] To reduce or avoid stray currents, at least a portion of the non-contact voltage measuring device 102 may be surrounded by a conductive internal grounding protection element or shield 132, which allows most of the current to flow through the coupling capacitor (C) formed with the conductor 122 of the insulated wire 106. O The conductive sensor 126. The internal grounding protection 132 may be formed of any suitable conductive material (e.g., copper) and may be solid (e.g., foil) or have one or more openings (e.g., mesh). The protection 132 surrounding the sensor 126 also reduces stray effects from adjacent wires near the sensor 126 during measurement.

[0035] The non-contact voltage measuring device 102 includes a mechanical oscillator 144 electrically coupled to a conductive sensor 126. In operation, the mechanical oscillator 144 causes the conductive sensor 126 to move according to the mechanical oscillation amplitude and frequency (f). O Mechanical oscillation is performed. The mechanical oscillator 144 causes the conductive sensor 126 to oscillate in the direction of the insulating conductor 106 to be measured, such that the distance (d) between the conductive sensor 126 and the insulating conductor 106 varies periodically according to the amplitude and frequency of the mechanical oscillation. This mechanical oscillation alters the coupling capacitor (C) exposed to the electric field. O Therefore, a value with an oscillation frequency (f) is generated in sensor 126. O ) signal current (I O The current is proportional to the electric field. As described below, the common-mode reference source 130 is used to utilize a frequency different from the oscillation frequency (f). O Injecting a known frequency (f) into the sensor R ) and amplitude (V) R The reference signal is used to generate a reference current I. R Therefore, according to formula (1), independent of the coupling capacitor C... O To determine the unknown DC voltage in the conductor 106 under test, as described below.

[0036] The mechanical oscillator 144 can be any suitable device or component for causing the conductive sensor 126 to mechanically oscillate or vibrate relative to an insulating conductor. Non-limiting examples of mechanical oscillators that can be used include piezoelectric oscillators or micromechanical system (MEMS) oscillators.

[0037] To prevent current from flowing between the internal grounding protection 132 and the external grounding terminal 128, the non-contact voltage measuring device 102 includes a conductive reference shield 134. The reference shield 134 can be formed of any suitable conductive material (e.g., copper) and can be solid (e.g., a sheet of metal, sputtered metal within a plastic housing), flexible (e.g., a foil), or have one or more openings (e.g., a mesh). A common-mode reference voltage source 130 is electrically coupled between the reference shield 134 and the internal grounding protection 132, which generates a reference voltage (V) for the non-contact DC voltage measuring device 102. R ) and reference frequency (f R The common-mode voltage or reference signal. This type of AC reference voltage (V) R ) drive additional reference current (I R ) through coupling capacitor (C O ) and body capacitor (C B ).

[0038] An internal grounding protection element 132 surrounding at least a portion of the conductive sensor 126 protects the conductive sensor from the AC reference voltage (V). R The direct impact of this effect causes a decrease in the reference current (I) between the conductive sensor 126 and the reference shield 134. R Undesirable offset may occur. As described above, the internal grounding protection 132 is the internal electronic ground terminal 138 for the non-contact voltage measuring device 102. In at least some embodiments, the internal grounding protection 132 also surrounds some or all of the electronics of the non-contact voltage measuring device 102 to prevent the AC reference voltage (V) from being applied. R It is coupled into electronic devices.

[0039] As described above, the reference shield 134 is used to inject an AC reference signal into the oscillation and amplitude (V) of the DC voltage. DC The input AC voltage signal (V) generated AC On top of this, and as a secondary function, minimize the capacitance of the protective element 132 to the ground terminal 128. In at least some embodiments, the reference shield 134 surrounds part or all of the housing 108 of the non-contact voltage measuring device 102. In such embodiments, some or all of the electronics refer to a reference common-mode signal, which also generates a reference current (I0) between the conductive sensor 126 and the conductor 122 in the insulated wire 106. RIn at least some specific embodiments, the only gap in the reference shield 134 may be an opening for the conductive sensor 126, which allows the conductive sensor to be positioned close to the insulated wire 106 during operation of the non-contact voltage measuring device 102.

[0040] Internal grounding protection 132 and reference shield 134 provide a housing 108 surrounding the non-contact voltage measuring device 102 (see Figure 1A and Figure 1B The reference shield 134 can be disposed on the outer surface of the housing 108, and the internal grounding protection 132 can be used as an internal shield or protection. The conductive sensor 126 shields the reference shield 134 through the protection 132, so that any reference current is transmitted through the coupling capacitor (C) between the conductive sensor 126 and the conductor under test 122. O The protective element 132 surrounding the sensor 126 also reduces stray effects from adjacent wires near the sensor.

[0041] like Figure 2 As shown, the conductive sensor 126 can be positioned near the insulating conductor 106 under test during measurement. The conductor 122 of the insulating conductor 106 under test is used as a coupling capacitor (C). O The first conductive element or electrode of the coupling capacitor is the vibration conductive sensor 126, which serves as the second conductive element or electrode of the coupling capacitor.

[0042] The non-contact voltage measurement device 102 may include a sensor signal measurement subsystem, for example, in the form of an input amplifier 136 that operates as an inverting current-to-voltage converter. The input amplifier 136 has a non-inverting terminal electrically coupled to an internal ground protection element 132, which serves as an internal ground 138 for the non-contact voltage measurement device 102. The inverting terminal of the input amplifier 136 may be electrically coupled to a conductive sensor 126. A feedback circuit 137 (e.g., a feedback resistor) may also be coupled between the inverting terminal and the output terminal of the input amplifier 136 to provide feedback and appropriate gain for input signal conditioning.

[0043] Input amplifier 136 receives signal current (I) from conductive sensor 126. O ) and reference current (I R The current is received and converted into a sensor current voltage signal that indicates the conductive sensor current at the output terminal of the input amplifier. This sensor current voltage signal can be, for example, an analog voltage. This analog voltage can be fed to a signal processing or control module 140, as discussed further below, which processes the sensor current voltage signal to determine the DC voltage (V) in the conductor 122 of the insulated wire 106. DCThe signal processing module 140 may include any combination of digital and / or analog circuitry, and may include an analog-to-digital converter (ADC), one or more processors, one or more non-transitory processor-readable storage media, etc.

[0044] Figure 3 This is a block diagram of a non-contact DC voltage measuring device 300, showing the various signal processing components of the device. The non-contact DC voltage measuring device 300 may be similar to or identical to the non-contact DC voltage measuring device 102 described above. Therefore, similar or identical components are labeled with the same reference numerals. As shown, the input amplifier 136 converts the input current (I0) from the conductive sensor 126 into signal processing components. O + I R The sensor current and voltage signals are converted into sensor current and voltage signals that indicate the input current. An analog-to-digital converter (ADC) 302 is then used to convert the sensor current and voltage signals into digital form.

[0045] DC voltage (V) in wire 122 DC ) and by constant vibration and reference voltage (V R AC voltage (V) caused by ) AC Related to AC voltage (V) AC It can be determined by equation (1):

[0046]

[0047] Among them (I) O ) is due to the DC voltage (V) in conductor 122 DC The AC signal current passing through the conductive sensor 126 due to mechanical oscillations, (I) R ) is due to the AC reference voltage (V R And through the reference current of the conductive sensor 126, (f O ) is the oscillation frequency of sensor 126, and (f R ) is the AC reference voltage (V R The frequency of ). The DC voltage (V) in conductor 122. DC ) can be obtained by using (V) from equation (1) AC The result is calculated by multiplying by a constant factor k, as shown in equations (1a) and (1b) below:

[0048]

[0049] This factor k is proportional to the mechanical oscillation frequency and the mechanical quantity of the oscillation. This factor k can be determined using a known DC voltage and a calculated V. AC It is determined by a single measurement.

[0050] Signals indexed as "0" or "AC" (e.g., I) O V AC ) and from frequency f O The AC component caused by the oscillation is related to the signal indexed as "DC" and is associated with the oscillating coupling capacitor (C). O The DC voltage (V) that generates a DC electric field within the ) DC The AC parameters have different characteristics than the signal indexed "R," such as frequency, which is related to the common-mode reference voltage source 130. Digital processing circuitry, such as implementing a Fast Fourier Transform (FFT) algorithm 306, can be used to separate signal values ​​with different frequencies. In other implementations, analog electronic filters can also be used to separate the characteristics of the "O" signal (e.g., magnitude, frequency) from those of the "R" signal.

[0051] Current (I) O ) and (I R Due to the coupling capacitor (C) O And respectively depend on the frequency (f) O ) and (f R ). Flow through the coupling capacitor (C) O ) and volume capacitance (C B The current is proportional to the frequency. The oscillation frequency (f) can be measured. O ) and reference frequency (f R ), or they may already be known, since the system generates oscillations and a reference voltage.

[0052] In the input current (I) O + I R After being regulated by input amplifier 136 and digitized by ADC 302, the frequency components of the digital sensor current-voltage signal can be determined by representing the signal in the frequency domain using FFT 306. When the frequency (f) has been measured or otherwise obtained... O ) and (f R When both are used, a frequency window can be determined to calculate the current (I) from the FFT 306. O ) and (I R The basic value of ).

[0053] Current (I) R ) and / or current (I O The value of the measured current (I) can vary depending on the distance between the reference signal sensor or electrode (e.g., electrode 126) and the conductor 122 of the insulated wire 106. Therefore, the system can measure the current (I) R ) and / or current (I O The distance between the reference signal sensor or electrode and conductor 122 is determined by comparing it with the expected current.

[0054] Next, as Figure 3 As shown in box 308, the frequency (f) can be determined or obtained. O ) and (f R To correct the current (I) R ) and (I O The ratio of the fundamental frequency to the fundamental frequency can be used to calculate the DC voltage (V) in wire 122. DC ).

[0055] Coupling capacitor (C) O Typically, the capacitance value can range from about 0.02 pF to 1 pF, depending, for example, on the distance between the insulating conductor 106 and the conductive sensor 126, as well as the specific shape and size of the sensor 126. Bulk capacitance (C) B It may have a capacitance value of approximately 20pF to 200pF.

[0056] From the above formula (1), it can be seen that the AC reference voltage (V) generated by the common-mode reference voltage source 130 R It is not necessary to be located at the AC voltage (V) generated by the vibration in conductor 122. AC To achieve the same range for signal current (I) O ) and reference current (I R A similar current value. By selecting a relatively high reference frequency (f R AC reference voltage (V) R The voltage may be relatively low (e.g., less than 5V).

[0057] Any suitable signal generator can be used to generate a signal with a reference frequency (f). R AC reference voltage (V) R ).exist Figure 3 In the illustrated embodiment, a Σ-Δ digital-to-analog converter (Σ-Δ DAC) 310 is used. The Σ-Δ DAC 310 uses a bitstream to generate a signal with a defined reference frequency (f). R ) and AC reference voltage (V R The Σ-Δ DAC 310 generates a waveform (e.g., a sinusoidal waveform) signal. In at least some specific implementations, the Σ-Δ DAC 310 can generate a waveform in phase with the window of the FFT 306 to reduce jitter. Any other reference voltage generator can be used, such as a PWM that uses less computational power than the Σ-Δ DAC.

[0058] Current flows through the coupling capacitor (C) O The sensor current (I) O ) and the voltage across the coupling capacitor (V DC) and the time-varying capacitance of the coupling capacitor caused by the vibration of the non-contact conductive sensor 126 ( C / t) is proportional. This relationship can be expressed by the following formula (2):

[0059]

[0060] Where k1 is a proportionality constant. The constant k1 may depend on at least one of the following: the physical characteristics of the conductive sensor 126, the physical characteristics of the insulating conductor 106 under test, or the physical characteristics of the space between the conductive sensor and the insulating conductor during measurement. For example, the constant k1 may depend on the specific shape of the conductive sensor 126, the area of ​​the conductive sensor, the dielectric constant of the volume between the conductive sensor and the insulating conductor under test, etc.

[0061] Rearrange the above formula (2), DC voltage (V) DC It can be determined as follows:

[0062]

[0063] Where k2 is a proportionality constant equal to 1 / k1. Time-varying capacitance ( C / t) depends on the mechanical oscillation amplitude, which determines the periodic change in the spacing distance (d) between the conductive sensor 126 and the insulating conductor 106 when the conductive sensor 126 vibrates. Time-varying capacitance ( C / t) also depends on the mechanical oscillation frequency (f) of the conductive sensor 126. O ).

[0064] As a simplified example, the conductive sensor 126 and the conductor under test 106 can be modeled as a parallel-plate capacitor (C) during measurement. O A parallel-plate capacitor has a capacitance (C) defined by the following formula (4):

[0065]

[0066] Where Q is the charge on the parallel plates, V is the voltage across the capacitor, (ε) is the dielectric constant of the capacitor, (A) is the area of ​​the parallel plates, and (d) is the distance between the two plates. Furthermore, the current flowing in the capacitor (I) O It can be defined by the following formula (5):

[0067] .

[0068] Using the above formulas (4) and (5), the current in the capacitor can be defined by the following formula (6):

[0069]

[0070] Equation (5) can then be rearranged to determine the voltage (V) across the capacitor based on the signal current, mechanical oscillation amplitude, and mechanical oscillation frequency. If the distance (d) between the conductor and the sensor is known, equation (6) can be solved. However, the distance (d) may not be known, so it may be necessary to use a reference signal to solve for the coupling capacitance (C). O Equations unrelated to ) are shown above in equations (1), (1a) and (1b).

[0071] During implementation, the measuring device 102 may use one or more mathematical formulas, lookup tables, and / or calibration factors to measure the detected signal current (I0). O Determine the DC voltage (V) in the insulated conductor 106. DC As described above, in at least some specific embodiments, the measuring device 102 is operable to measure one or more other electrical parameters, such as current, power, phase angle, etc.

[0072] The non-contact voltage measurement device 102 may also include one or more interfaces 142 communicatively coupled to the signal processing module 140. The one or more interfaces 142 may include one or more input or output components of a user interface, such as one or more displays, speakers, touchpads, touchscreens, buttons, dials, knobs, wheels, etc. The one or more interfaces 142 may additionally or alternatively include one or more wired or wireless communication interfaces, such as USB interfaces, Bluetooth interfaces, etc. ® Interfaces such as Wi-Fi interfaces are included. Various interfaces 142 allow interaction with non-contact voltage measurement devices 102, such as outputting a defined DC voltage (V). DC This information may be transmitted to the operator 104 of a non-contact voltage measuring device. One or more communication interfaces may be used to transmit data (e.g., measurement data) to or receive data (e.g., control commands) from an external system.

[0073] Figure 4 This is a block diagram of the signal processing section 400 of a non-contact voltage measurement system implementing an electronic filter. The signal processing section 400 receives current (IL) from the current measurement subsystem 401 (e.g., input amplifier 136) and the current (IL) from the conductivity sensor 126. O + I R The sensor current and voltage signals are proportional.

[0074] As mentioned above, the signal current (I) O ) has the same characteristics as the reference current (I) R Different frequencies. In order to convert the signal current (I) to different frequencies. O) and reference current (I R The signal processing section 400 may include a first filter 402, which is used to isolate the signal current (I) from the signal processing section 400. O ) Passes and rejects the reference current (I) R The filtered signal can then be rectified by the first rectifier 404 and digitized by the first ADC 406. The digitized signal can then be fed to the appropriate processor 408 for calculation, as described above. Similarly, in order to convert the reference current (I... R ) and signal current (I O The signal processing section 400 may include a second filter 410, which is used to isolate the reference current (I) from the signal processing section 400. R ) allows and rejects signal current (I) O The filtered signal can then be rectified by the second rectifier 412 and digitized by the second ADC 414. The digitized signal can then be fed to a suitable processor 408 for computation. The first filter 402 and the second filter 410 can be any suitable analog filter and may each include multiple discrete components (e.g., capacitors, inductors).

[0075] The foregoing specific embodiments have illustrated various specific implementations of the apparatus and / or process using block diagrams, schematic diagrams, and examples. Where such block diagrams, schematic diagrams, and examples contain one or more functions and / or operations, those skilled in the art will understand that each function and / or operation within such block diagrams, flowcharts, or examples can be implemented individually and / or collectively by a wide range of hardware, software, firmware, or virtually any combination thereof. In one specific embodiment, this subject matter can be implemented using an application-specific integrated circuit (ASIC). However, those skilled in the art will recognize that the specific embodiments disclosed herein can be equivalently implemented, in whole or in part, in standard integrated circuits as one or more computer programs running on one or more computers (e.g., one or more programs running on one or more computer systems), one or more programs running on one or more controllers (e.g., microcontrollers), one or more programs running on one or more processors (e.g., microprocessors), firmware, or virtually any combination thereof, and that, in light of this disclosure, designing circuitry and / or writing code for the software and / or firmware will be entirely within the skill of those skilled in the art.

[0076] Those skilled in the art will recognize that many of the methods or algorithms described herein may employ additional actions, omit certain actions, and / or be able to perform actions in a different order than specified. For example, in at least some embodiments, the non-contact voltage measurement system may not utilize a processor to execute instructions. For example, the non-contact voltage measurement device may be hardwired to provide some or all of the functionality discussed herein. Additionally, in at least some embodiments, the non-contact voltage measurement device may not utilize a processor to initiate or trigger the different measurements discussed herein. For example, such a non-contact voltage measurement device may rely on one or more individual inputs, such as a user-actuated button that causes a measurement to occur.

[0077] Furthermore, those skilled in the art will understand that the mechanisms described herein can be distributed as various forms of program products, and the exemplary embodiments are equally applicable regardless of the specific type of signal-bearing medium used to actually implement the distribution. Examples of signal-bearing media include, but are not limited to, recordable media such as floppy disks, hard disk drives, CD-ROMs, digital magnetic tapes, and computer memory.

[0078] The various embodiments described above can be combined to provide further embodiments. In view of the specific embodiments described above, these and other changes can be made to these embodiments. Generally, the terminology used in the following claims should not be construed as limiting the claims to the embodiments disclosed in this specification and claims, but should be construed as including all possible embodiments and the full scope of equivalents conferred by these claims. Therefore, the claims are not limited by this disclosure.

Claims

1. An apparatus for measuring direct current (DC) voltage in an insulated conductor, the apparatus comprising: A conductive sensor that can selectively locate near the insulating conductor without making electrical contact with the insulating conductor; An internal grounding protection device is electrically isolated from the conductive sensor. A reference shield, which is electrically insulated from the internal grounding protection component; A mechanical oscillator operatively coupled to the conductive sensor, wherein the mechanical oscillator causes mechanical oscillation of the conductive sensor during operation, such that the distance between the conductive sensor and the insulating conductor varies according to the mechanical oscillation; A common-mode reference voltage source that generates an alternating current (AC) reference voltage during operation, the common-mode reference voltage source being electrically coupled between the internal grounding protection and the reference shield; A sensor signal measurement subsystem electrically coupled to the conductive sensor, wherein the sensor signal measurement subsystem generates a sensor current signal indicating the current conducted through the conductive sensor during operation; and A control circuit, communicatively coupled to the sensor signal measurement subsystem, wherein in operation, the control circuit: Receive the sensor current signal from the sensor signal measurement subsystem; as well as The DC voltage in the insulating conductor is determined at least in part based on the sensor current signal and the frequency of the mechanical oscillator.

2. The device of claim 1, wherein the control circuitry determines the DC voltage in the insulating conductor based at least in part on the sensor current signal, the frequency of the mechanical oscillator, the AC reference voltage, and the reference frequency of the AC reference voltage.

3. The device according to claim 1, wherein the mechanical oscillator comprises a piezoelectric mechanical oscillator.

4. The device according to claim 1, wherein the mechanical oscillator comprises a microelectromechanical oscillator.

5. The device according to claim 2, wherein the control circuit, during operation: Convert the sensor current signal into a digital signal; and The digital signal is processed to obtain a frequency domain representation of the sensor current signal.

6. The device of claim 5, wherein the control circuit implements a Fast Fourier Transform (FFT) to obtain the frequency domain representation of the sensor current signal.

7. The device of claim 6, wherein the common-mode reference voltage source generates the AC reference voltage that is in phase with the window of the FFT implemented by the control circuit.

8. The device of claim 1, wherein the control circuitry includes at least one electronic filter for filtering the sensor current signal.

9. The device of claim 2, wherein the control circuit processes the sensor current signal to determine an insulating conductor current component and a reference current component, the insulating conductor current component indicating the current conducted through the conductive sensor due to the voltage in the insulating conductor, and the reference current component indicating the current conducted through the conductive sensor due to the voltage of the common-mode reference voltage source.

10. The device of claim 9, wherein the control circuit determines the frequency of the insulating conductor current component of the sensor current signal.

11. The device of claim 1, wherein in operation, the sensor signal measurement subsystem receives an input current from the conductive sensor, and the sensor current signal includes a voltage signal indicating the input current received from the conductive sensor.

12. A method of operating an apparatus to measure a direct current (DC) voltage in an insulated conductor, said apparatus comprising: A conductive sensor capable of selectively positioning near an insulating conductor without making electrical contact with the insulating conductor; An internal grounding protection element that at least partially surrounds and is electrically isolated from the conductive sensor; The method includes: a conductive reference shield electrically insulated from the internal grounding protection element; and a conductive reference shield electrically insulated from the internal grounding protection element. The mechanical oscillation caused by the mechanical oscillation causes the distance between the conductive sensor and the insulating conductor to change accordingly. This causes the common-mode reference voltage source to generate an AC reference voltage, which is electrically coupled between the internal grounding protection component and the conductive reference shield. Generate a sensor current signal that indicates the current conducted through the conductive sensor; Receive the sensor current signal; and The DC voltage in the insulating conductor is determined by the control circuit based at least in part on the sensor current signal and the mechanical oscillation frequency of the mechanical oscillation.

13. The method of claim 12, wherein generating the sensor current signal comprises: Receive input current from the conductive sensor; as well as A voltage signal is generated that indicates the input current received from the conductive sensor.

14. The method of claim 12, wherein the sensor current signal is generated using an operational amplifier operating as a current-to-voltage converter.

15. The method of claim 12, wherein mechanically oscillating the conductive sensor comprises using a piezoelectric mechanical oscillator to mechanically oscillate the conductive sensor.

16. The method of claim 12, wherein mechanically oscillating the conductive sensor comprises using a microelectromechanical oscillator to mechanically oscillate the conductive sensor.

17. The method of claim 12, wherein determining the DC voltage in the insulating conductor comprises: The sensor current signal is converted into a digital signal by at least one processor; as well as The digital signal is processed by the at least one processor to obtain a frequency domain representation of the sensor current signal.

18. An apparatus for measuring direct current (DC) voltage in an insulated conductor, the apparatus comprising: A conductive sensor that can selectively locate near the insulating conductor without making electrical contact with the insulating conductor; A mechanical oscillator operatively coupled to the conductive sensor, wherein the mechanical oscillator causes the conductive sensor to mechanically oscillate during operation to change the capacitance between the conductive sensor and the insulating conductor relative to time; An internal grounding protection device is electrically isolated from the conductive sensor. A reference shield, which is electrically insulated from the internal grounding protection component; A common-mode reference voltage source that generates an alternating current (AC) reference voltage during operation, the common-mode reference voltage source being electrically coupled between the internal grounding protection and the reference shield; A sensor signal measurement subsystem electrically coupled to the conductive sensor, wherein the sensor signal measurement subsystem generates a sensor current signal indicating the current conducted through the conductive sensor during operation; and A control circuit, communicatively coupled to the sensor signal measurement subsystem, wherein in operation, the control circuit: Receive the sensor current signal from the sensor signal measurement subsystem; as well as The DC voltage in the insulating conductor is determined at least in part based on the sensor current signal and the frequency of the mechanical oscillator.

19. The device of claim 18, wherein in operation, the control circuitry determines the DC voltage in the insulating conductor based on the sensor current signal and on the capacitance change over time between the conductive sensor and the insulating conductor.

20. The device of claim 18, wherein the mechanical oscillator comprises at least one of a piezoelectric mechanical oscillator or a microelectromechanical oscillator.

Images