Multi-sensor configuration for non-contact voltage measurement devices

Abstract

To provide systems and methods for measuring AC voltage of an insulated conductor without requiring a galvanic connection between the conductor and a test electrode or probe.SOLUTION: A system includes a sensor subsystem, an internal ground guard 132 and a reference shield 134. A common mode reference voltage source 130 is electrically coupled between the internal ground guard 132 and the reference shield 134 to generate an AC reference voltage which causes a reference current to pass through the conductive sensor 126. Control circuitry receives a signal indicative of current flowing through the sensor subsystem due to the AC reference voltage and the AC voltage in the insulated conductor 122, and determines the AC voltage in the insulated conductor 122 based at least in part on the received signal. The sensor subsystem includes at least two independent sensors that are used to compensate for conductor position while improving accuracy and dynamic range.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates generally to voltage measurement devices, and more particularly to sensors for voltage measurement devices. [Background technology]

[0002] A voltmeter is an instrument used to measure voltage in an electrical circuit. Instruments that measure more than one electrical property are called multimeters or digital multimeters (DMMs) and operate to measure several parameters commonly required for service, troubleshooting, and maintenance applications. Such parameters typically include alternating current (AC) voltage and current, direct current (DC) voltage and current, and resistance or continuity. Other parameters, such as power quality, frequency, capacitance, and temperature, can also be measured to meet the requirements of a particular application.

[0003] When using a conventional voltmeter or multimeter to measure AC voltage, it is necessary to make galvanic contact of at least two measurement electrodes or probes with a conductor, and in many cases it is necessary to cut off the insulation of an insulated wire or provide a terminal for measurement in advance. Besides requiring an exposed wire or terminal for galvanic contact, the process of applying a voltmeter probe to a stripped wire or terminal can be relatively dangerous due to the risk of shock or electrocution. "Non-contact" voltage measurement devices are sometimes used to detect the presence of alternating current (AC) voltage without requiring galvanic contact with the circuit. When a voltage is detected, the user is alerted by an indication such as a light, a buzzer, or a vibration motor. However, such non-contact voltage detectors only indicate the presence or absence of AC voltage, but do not indicate the actual magnitude (e.g., RMS value) of the AC voltage. [Problem to be solved by the invention]

[0004] Therefore, a need exists for an AC voltage measurement system that provides convenient and accurate voltage measurements without the need for galvanic contact with the circuit being tested. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] U.S. Patent No. 8,330,449 [Patent Document 2] U.S. Patent No. 5,473,244 Summary of the Invention [Means for solving the problem]

[0006] An apparatus for measuring alternating current (AC) in an insulated conductor may be summarized as follows: the apparatus includes a housing and a sensor subsystem physically coupled to the housing, the sensor subsystem comprising: insulationa conductive internal ground guard at least partially surrounding the sensor subsystem and galvanically isolated from the sensor subsystem, the internal ground guard being sized and dimensioned to shield the sensor subsystem from stray currents; a conductive reference shield surrounding at least a portion of the housing and galvanically isolated from the internal ground guard, the conductive reference shield being sized and dimensioned to reduce currents between the internal ground guard and an external ground; and a common mode reference voltage source that, during operation, generates an alternating current (AC) reference voltage having a reference frequency, the common mode reference voltage source generating an AC reference voltage having a reference frequency, the common mode reference voltage source being configured to generate an AC reference voltage having a reference frequency; a common mode reference voltage source, the voltage source electrically coupled between the internal ground guard and the conductive reference shield; an input voltage signal conditioning circuit selectively and alternately couplable to a first sensor portion and a second sensor portion of the sensor subsystem, the input voltage signal conditioning circuit generating, during operation, a sensor current signal indicative of a current conducted through the sensor subsystem due to an input voltage in the insulated conductor under test; a reference signal conditioning circuit selectively and alternately couplable to the first sensor portion and the second sensor portion of the sensor subsystem, the reference signal conditioning circuit generating, during operation, a sensor current signal indicative of a current conducted through the sensor subsystem due to an AC reference voltage detected in the insulated conductor under test; and a control circuit communicatively coupled to the input voltage signal conditioning circuit and the reference signal conditioning circuit, wherein, during operation, the control circuit receives the sensor current signal from each of the input voltage signal conditioning circuit and the reference signal conditioning circuit. , Se and a control circuit that determines an AC voltage in the insulated conductor based at least in part on the sensor current signal, the AC reference voltage, and the reference frequency.

[0007] The first sensor portion may include a first plurality of spaced apart conductive sensors electrically coupled together, and the second sensor portion may include a second plurality of spaced apart conductive sensors electrically coupled together. The first plurality of conductive sensors of the first sensor portion may be interleaved with the second plurality of conductive sensors of the second sensor portion. The input voltage signal conditioning circuit may be selectively and alternately couplable to the first sensor portion and the second sensor portion via a first switch, and the reference signal conditioning circuit may be selectively and alternately couplable to the first sensor portion and the second sensor portion via a second switch. The control circuit may synchronously control the states of the first and second switches during operation to alternately electrically couple the first sensor portion to the reference signal conditioning circuit and the second sensor portion to the input voltage signal conditioning circuit, and electrically couple the second sensor portion to the reference signal conditioning circuit and the first sensor portion to the input voltage signal conditioning circuit. The control circuit may synchronously control the states of the first and second switches during operation with a 50 percent duty cycle. The control circuitry can determine, during operation, which of the first and second sensor portions produces a maximum sensor current signal and can determine an AC voltage in the insulated conductor based at least in part on the determination of which of the first and second sensor portions produces a maximum sensor current signal. The control circuitry can determine, during operation, which of the first and second sensor portions produces a maximum sensor current signal, can ignore the sensor current signal obtained from the one of the first and second sensor portions that produces the minimum sensor current signal, and can determine an AC voltage in the insulated conductor based at least in part on the sensor current signal obtained from the one of the first and second sensor portions that produces the maximum sensor current signal. The control circuitry can determine, during operation, which of the first and second sensor portions produces a maximum sensor current signal and can ignore the sensor current signal obtained from the one of the first and second sensor portions that produces the minimum sensor current signal and can determine an AC voltage in the insulated conductor based at least in part on the sensor current signal obtained from the one of the first and second sensor portions that produces the maximum sensor current signal. , Se A weighted combination of the sensor current signals can be determined, and , Se Based at least in part on the weighted combination of the sensor current signals, an AC voltage in the insulated conductor can be determined. SThe weighted combination of the sensor current signals may include at least one of a linear weighted combination or an exponential weighted combination. Each of the input voltage signal conditioning circuit and the reference signal conditioning circuit may include at least one of an amplifier, a filter, or an analog-to-digital converter. The input voltage signal conditioning circuit may be optimized to condition or process an input voltage signal, and the reference signal conditioning circuit may be optimized to condition or process an AC reference voltage signal. The sensor subsystem and the conductive internal ground guard may each be non-planar. The control circuit may take a first measurement when the common mode reference voltage source is disabled, may take a second measurement when the common mode reference voltage source is enabled, and may determine an AC voltage in the insulated conductor based at least in part on the first and second measurements, the AC reference voltage, and the reference frequency.

[0008] A method of operating an apparatus for measuring alternating current (AC) voltage in an insulated conductor may be summarized as follows: the apparatus includes a housing and a sensor subsystem physically coupled to the housing, the sensor subsystem comprising: insulationa sensor subsystem selectively positionable proximate to the insulated conductor without galvanically contacting the conductor, the sensor subsystem capacitively coupling to the insulated conductor, the sensor subsystem including a first sensor portion and a second sensor portion independent of the first sensor portion; a conductive internal ground guard at least partially surrounding the sensor subsystem and galvanically isolated from the sensor subsystem, the internal ground guard sized and dimensioned to shield the sensor subsystem from stray currents; and a conductive reference shield surrounding at least a portion of the housing and galvanically isolated from the internal ground guard, the conductive reference shield sized and dimensioned to reduce current flow between the internal ground guard and an external ground, the method comprising: generating an alternating current (AC) reference voltage having a reference frequency, the common mode reference voltage source being electrically coupled between the internal ground guard and the conductive reference shield; generating a sensor current signal indicative of a current conducted through the sensor subsystem due to an input voltage detected at the insulated conductor under test via an input voltage signal conditioning circuit alternately electrically coupleable to the first and second sensor portions of the sensor subsystem; generating a sensor current signal indicative of a current conducted through the sensor subsystem due to an AC reference voltage detected at the insulated conductor under test via a reference current signal conditioning circuit alternately electrically coupleable to the first and second sensor portions of the sensor subsystem; receiving, by a control circuit, the sensor current signal from each of the input voltage signal conditioning circuit and the reference signal conditioning circuit; , Se and determining an AC voltage in the insulated conductor based at least in part on the sensor current signal, the AC reference voltage, and the reference frequency.

[0009] An apparatus for measuring alternating current (AC) in an insulated conductor may be summarized as follows: the apparatus includes a first sensor portion including a first plurality of conductive sensors; a second sensor portion independent of the first sensor portion, the second sensor portion including a second plurality of conductive sensors; an input voltage signal conditioning circuit that, during operation, generates a sensor current signal indicative of a current conducted through at least one of the first sensor portion and the second sensor portion due to an input voltage in the insulated conductor under test; and an input voltage signal conditioning circuit that, during operation, generates a sensor current signal indicative of a current conducted through at least one of the first sensor portion and the second sensor portion due to an AC reference voltage generated by the apparatus and detected in the insulated conductor under test. 1. Sensors at least one of the first sensor portion and the second sensor portion a reference signal conditioning circuit that generates a sensor current signal indicative of a current conducted through the input voltage signal conditioning circuit; a first controllable switch that operates to alternatively couple each of the first sensor portion and the second sensor portion to the input voltage signal conditioning circuit; and a second controllable switch that operates to alternatively couple each of the first sensor portion and the second sensor portion to the reference signal conditioning circuit.

[0010] The apparatus may further include a control circuit communicatively coupled to the input voltage signal conditioning circuit, the reference signal conditioning circuit, the first controllable switch, and the second controllable switch, wherein during operation, the control circuit controls the first controllable switch to alternately couple the first sensor portion to the input voltage signal conditioning circuit and the second sensor portion to the input voltage signal conditioning circuit, controls the second controllable switch to alternately couple the first sensor portion to the reference signal conditioning circuit and the second sensor portion to the reference signal conditioning circuit, and receives a sensor current signal from each of the input voltage signal conditioning circuit and the reference signal conditioning circuit. , Seand determining an AC voltage in the insulated conductor based at least in part on the sensor current signal. The control circuit can synchronously control states of the first and second controllable switches with a 50 percent duty cycle during operation. The first sensor portion can include a first plurality of spaced apart conductive sensors electrically coupled together and the second sensor portion can include a second plurality of spaced apart conductive sensors electrically coupled together. The first plurality of conductive sensors of the first sensor portion can be interleaved with the second plurality of conductive sensors of the second sensor portion. [Brief description of the drawings]

[0011] In the drawings, similar elements or functions are identified by the same reference numbers. The dimensions and relative positions of elements in the drawings are not necessarily drawn to scale. For example, the shapes of the various elements and angles are not necessarily drawn to scale, and some of these elements may be arbitrarily enlarged and positioned to improve the clarity of the drawings. It is noted that the particular shapes of the elements as shown are not necessarily intended to convey any information regarding the actual shape of the particular elements, but may simply be selected for ease of recognition in the drawings.

[0012] [Figure 1A] FIG. 1A is a pictorial diagram of an environment in which an operator can use a non-contact voltage measurement device including a reference signal type voltage sensor, according to one illustrated embodiment, to measure AC voltage present in an insulated electrical wire without requiring galvanic contact with the wire. [Figure 1B] FIG. 1B is a top view of the non-contact voltage measurement device of FIG. 1A showing the coupling capacitance formed between the insulated wire and a conductive sensor of the non-contact voltage measurement device, the insulated conductor current components, and the human body capacitance between the non-contact voltage measurement device and an operator, according to one illustrated embodiment. [Diagram 2] FIG. 2 is a schematic diagram of various internal components of a non-contact voltage measurement device, according to one illustrated embodiment. [Diagram 3]FIG. 3 is a block diagram illustrating various signal processing components of a non-contact voltage measurement device, according to one illustrated embodiment. [Figure 4] FIG. 4 is a schematic diagram of a non-contact voltage measurement device implementing a Fast Fourier Transform (FFT), according to one illustrated embodiment. [Diagram 5] FIG. 5 is a schematic diagram of a sensor subsystem including a first sensor array portion having a first plurality of sensor elements and a second sensor array portion having a second plurality of sensor elements, where the first plurality of sensor elements are interleaved with the second plurality of sensor elements, according to one illustrated embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] One or more embodiments of the present disclosure are directed to systems and methods for measuring alternating current (AC) voltages of insulated or blank non-insulated conductors (e.g., insulated wires) without the need for a galvanic connection between the conductor and a test electrode or probe. In general, a non-galvanic contact (or "non-contact") voltage measurement system is provided, which measures the AC voltage signal in the insulated conductor relative to ground using a capacitive sensor. Such systems that do not require a galvanic connection are referred to herein as "non-contact." As used herein, "electrically coupled" includes both direct and indirect electrical coupling, unless otherwise specified. As discussed further below with reference to FIG. 5, in at least some embodiments, two independent sensors are used to provide improved measurements with compensation for the position of the conductor under test, and the signal path is split directly at the sensor input into a reference signal and an input signal by using signal separation methods such as filters, synchronous rectification, or other modulation methods. As discussed further below, this splitting can be used to, for example, independently optimize the sensitivity / range of the reference and input signals to improve performance / accuracy and reduce noise.

[0014] In the following description, certain specific details are set forth to provide a thorough understanding of various disclosed embodiments. However, those skilled in the art will understand that the embodiments can be practiced without one or more of these specific details, or with other methods, components, materials, etc. In other cases, well-known structures related to computer systems, server computers, and / or communication networks have not been shown or described in detail to avoid unnecessarily obscuring the description of the embodiments.

[0015] Unless the context requires otherwise, throughout the following specification and claims, the term "comprising" is synonymous with the term "including" and is inclusive and therefore non-exclusive (i.e., does not exclude additional, unrecited elements or method acts).

[0016] References throughout this specification to "one implementation" or "an implementation" mean that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment. Thus, the appearances of the phrases "in one implementation" or "in an implementation" in various places throughout this specification do not necessarily all refer to the same embodiment. However, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0017] As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the content clearly dictates otherwise. It should also be noted that the term "or" is used generally in its sense to include "and / or" unless the context clearly dictates otherwise.

[0018] The headings and abstracts provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.

[0019] The following discussion provides examples of systems and methods for measuring alternating current (AC) voltages of insulation (e.g., insulated wire) or blank non-insulated conductors (e.g., bus bars) without requiring a galvanic connection between the conductor and a test electrode or probe. The embodiments disclosed in this section may be referred to herein as "referenced signal type voltage sensors" or systems. Generally, a non-galvanic contact (or "non-contact") voltage measurement device is provided, where the system measures the AC voltage signal in the insulated conductor relative to ground using a capacitive sensor. Such systems that do not require a galvanic connection are referred to herein as "non-contact." As used herein, "electrically coupled" includes both direct and indirect electrical coupling, unless otherwise specified.

[0020] FIG. 1A is a pictorial diagram of an environment 100 in which a non-contact voltage measurement device 102, including a reference signal type voltage sensor or system, can be used by an operator 104 to measure an AC voltage present in an insulated electrical wire 106 without requiring galvanic contact between the non-contact voltage measurement device and the electrical wire 106. FIG. 1B is a top view of the non-contact voltage measurement device 102 of FIG. 1A illustrating various electrical characteristics of the non-contact voltage measurement device during operation. The non-contact voltage measurement device 102 includes a housing or body 108 that includes a gripping portion or end 110 and a probe portion or end 112, also referred to herein as a front end, opposite the gripping portion. The housing 108 can also include a user interface 114 to facilitate user interaction with the non-contact voltage measurement device 102. The user interface 114 can include any number of inputs (e.g., buttons, dials, switches, touch sensors) and any number of outputs (e.g., displays, LEDs, speakers, buzzers). The non-contact voltage measurement device 102 may also include one or more wired and / or wireless communication interfaces (eg, USB, Wi-Fi®, Bluetooth®).

[0021] In at least some embodiments, as best shown in FIG. 1B, the probe portion 112 can include a recessed portion 116 defined by a first extension portion 118 and a second extension portion 120. The recessed portion 116 receives the insulated wire 106 (see FIG. 1A). The insulated wire 106 includes a conductor 122 and an insulator 124 surrounding the conductor 122. The recessed portion 116 can include a sensor or electrode 126 that rests proximate to the insulator 124 of the insulated wire 106 when the insulated wire is positioned within the recessed portion 116 of the non-contact voltage measurement device 102. Although not shown for clarity, the sensor 126 can be disposed within the housing 108 to prevent physical and electrical contact between the sensor and other objects.

[0022] As shown in FIG. 1A, during use, an operator 104 can grasp the gripping portion 110 of the housing 108 and place the probe portion 112 in proximity to the insulated electrical wire 106 such that the non-contact voltage measurement device 102 can accurately measure the AC voltage present in the wire relative to earth ground (or another reference node). Although the probe end 112 is shown as having a recessed portion 116, in other embodiments, the probe portion 112 can be configured differently. For example, in at least some embodiments, the probe portion 112 can include a movable clamp, hook, selectively flat or arcuate surface including a sensor, or other type of interface that allows the sensor of the non-contact voltage measurement device 102 to be positioned in proximity to the insulated electrical wire 106. Examples of various probe portions and sensors are discussed below with reference to FIG. 5.

[0023] It may only be in some embodiments that the operator's body acts as the earth / ground reference. Alternatively, a direct connection to earth 128 via test lead 139 can be used. The non-contact measurement features discussed herein are not limited to applications where measurements are made relative to earth. The external reference can be capacitively or directly coupled to any other potential. For example, if the external reference is capacitively coupled to another phase of a three-phase system, the phase-to-phase voltage is measured. In general, the concepts discussed herein are not limited to references relative to earth using a body capacitively connected to a reference voltage and any other reference potential.

[0024] As discussed further below, in at least some embodiments, the non-contact voltage measurement device 102 detects the human body capacitance ( B ) can be used. Although the term ground is used for node 128, the node is not necessarily earth / ground but can be connected in a galvanically isolated manner to any other reference potential by capacitive coupling.

[0025] The particular systems and methods used by the non-contact voltage measurement device 102 to measure AC voltages are discussed below with reference to FIGS.

[0026] 2 shows a schematic diagram of various internal components of the non-contact voltage measurement device 102, which is also shown in FIGS. 1A and 1B. In this embodiment, the conductive sensor 126 of the non-contact voltage measurement device 102 is substantially "V-shaped" and is positioned proximate to the insulated wire 106 under test and capacitively couples with the conductor 122 of the insulated wire 106, forming a sensor coupling capacitor (C O The operator 104 who handles the non-contact voltage measuring device 102 forms a human body capacitance (C B ) to ground. Alternatively, a direct conductive ground coupling through a wire (e.g., test lead 139) can be used as shown in FIGS. 1A and 1B. Thus, as shown in FIGS. 1B and 2, the AC voltage signal (V O) is the insulated conductor current component or "signal current" (I O ) in series with a coupling capacitor (C O ) and human body capacity (C B ) in some embodiments. B ) may also include galvanically isolated test leads that create a capacitance to ground or any other reference potential.

[0027] The AC voltage (V O ) has a connection to an external ground 128 (e.g., neutral). The non-contact voltage measurement device 102 itself also has a capacitance to ground 128, which is primarily the human body capacitance ( B ) Capacity C O and C B A conductive loop is created by both the O ) is generated. O ) is the AC voltage signal (V O ) to the housing 108 of the non-contact voltage measurement device and to ground 128. B ) back to external ground 128. O ) depends on the distance between the conductive sensor 126 of the non-contact voltage measurement device 102 and the insulated wire 106 under test, the particular shape of the conductive sensor 126, and the size and voltage level (V O ) depends on

[0028] Signal current (I O ) and the associated coupling capacitance (C O To compensate for variations in the signal voltage frequency (f O ) and a different reference frequency (f R ) with an AC reference voltage (V R )

[0029] To reduce or avoid stray currents, at least a portion of the non-contact voltage measurement device 102 may be surrounded by a conductive internal grounded guard or screen 132, which directs most of the current through the conductive sensor 126, which is coupled to a coupling capacitor (C O ) is formed by the conductor 122 of the insulated wire 106. The internal ground guard 132 may be formed from any suitable conductive material (e.g., copper) and may be solid (e.g., foil) or may have one or more openings (e.g., mesh).

[0030] Additionally, to avoid current flow between the internal ground guard 132 and the external ground 128, the non-contact voltage measurement device 102 includes a conductive reference shield 134. The reference shield 134 may be formed from any suitable conductive material (e.g., copper) and may be solid (e.g., sheet metal), sputtered metal inside a plastic housing, flexible (e.g., foil), or have one or more openings (e.g., mesh). A common mode reference voltage source 130 is electrically coupled between the reference shield 134 and the internal ground guard 132, thereby providing a reference voltage (V R ) and the reference frequency (f R ) and a common-mode voltage or reference signal having such an AC reference voltage (V R ) provides an additional reference current (I R ) is the coupling capacitor (C O ) and human body capacitor (C B )

[0031] An internal ground guard 132 that surrounds at least a portion of the conductive sensor 126 provides a reference current (I R ) which causes an unwanted offset in the AC reference voltage (V R ) as described above, the internal ground guard 132 is the internal electronic ground 138 of the non-contact voltage measurement device 102. In at least some embodiments, the internal ground guard 132 also provides a reference AC voltage (VR ) to enclose some or all of the electronics of the non-contact voltage measurement device 102.

[0032] As described above, the reference shield 134 couples the reference signal to the input AC voltage signal (V O ) and as a second function, minimizes the guard 132 to earth ground 128 capacitance. In at least some embodiments, the reference shield 134 surrounds some or all of the housing 108 of the non-contact voltage measurement device 102. In such embodiments, some or all of the electronics are referenced to a reference common mode signal, which is a reference current (I R ), in at least some 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 in close proximity to the insulated wire 106 during operation of the non-contact voltage measurement device 102.

[0033] The internal ground guard 132 and the reference shield 134 can provide a dual layer screen around the housing 108 (see FIGS. 1A and 1B) of the non-contact voltage measurement device 102. The reference shield 134 can be located on the exterior surface 108 of the housing, and the internal ground guard 132 can function as an internal shield or guard. The conductive sensor 126 is shielded by the guard 132 to the reference shield 134, so that any reference current is coupled to the coupling capacitor (C O ) is generated between the conductive sensor 126 and the conductor 122 under test. The guard 132 around the sensor 126 also reduces the effects of stray electrical wires adjacent to the sensor.

[0034] 2, the non-contact voltage measurement device 102 can include 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 the internal ground guard 132 that serves as an internal ground 138 of the non-contact voltage measurement device 102. The inverting terminal of the input amplifier 136 can be electrically coupled to the conductive sensor 126. A feedback circuit 137 (e.g., a feedback resistor) can also be coupled between the inverting terminal and an output terminal of the input amplifier 136 to provide feedback and appropriate gain to condition the input signal.

[0035] The input amplifier 136 receives the signal current (I O ) and reference current (I R ) from the conductive sensor 126 and converts the received current into a sensor current voltage signal indicative of the conductive sensor current at the output terminals of the input amplifier. For example, the sensor current voltage signal may be an analog voltage. The analog voltage may be fed to a signal processing module 140, which processes the sensor current voltage signal to convert it into an AC voltage (V O ). The signal processing module 140 may include any combination of digital and / or analog circuitry.

[0036] The non-contact voltage measurement device 102 also measures the determined AC voltage (V O ) or communicate via an interface to an operator 104 of the non-contact voltage measurement device.

[0037] 3 is a block diagram of a non-contact voltage measurement device 300 showing various signal processing components of the non-contact voltage measurement device. FIG 4 is a more detailed diagram of the non-contact voltage measurement device 300 of FIG 3.

[0038] The non-contact voltage measurement device 300 may be similar or identical to the non-contact voltage measurement device 102 discussed above. Thus, similar or identical components are labeled with the same reference numbers. As shown, the input amplifier 136 receives the input current (I O +I R ) into a sensor current voltage signal indicative of the input current. The sensor current voltage signal is converted to digital form using an analog-to-digital converter (ADC) 302.

[0039] AC voltage of wire 122 (V O ) is calculated by the AC reference voltage (V R )

number

[0040] AC voltage (V O ) have different characteristics, such as frequency, than signals having an index "R" associated with the common mode reference voltage source 130. In the embodiment of FIG. 4, digital processing, such as a circuit implementing a Fast Fourier Transform (FFT) algorithm 306, can be used to separate the magnitudes of the signals at different frequencies. In other embodiments, analog electronic filters can be used to separate the "O" signal characteristics (e.g., magnitude, frequency) from the "R" signal characteristics.

[0041] Current (I O ) and (I R ) is the coupling capacitor (CO ) for frequency (f O ) and (f R ) depends on the coupling capacitor (C O ) and the human body capacitance (C B ) is proportional to frequency and therefore the AC voltage in the conductor 122 under test (V O ) frequency (f O ) is the reference frequency (f R ) and signal frequency (f O ) or that the reference frequency is known since it is generated by the system.

[0042] Input current (I O +I R After the frequency (f) is conditioned by the input amplifier 136 and digitized by the ADC 302, the frequency content of the digital sensor current / voltage signal can be determined by representing the signal in the frequency domain using an FFT 306. O ) and (f R ) are measured, the current (I O ) and (I R ) from the FFT 306, the frequency bins can be determined.

[0043] Current (I R ) and / or current (I O ) can vary as a function of the distance between a reference signal sensor or electrode (e.g., electrode 126) of the insulated wire 106 and the conductor 122. Thus, the system can measure the magnitude of the measured current (I R ) and / or current (I O ) can be compared to the expected respective current to determine the distance between the reference signal sensor or electrode and the conductor 122.

[0044] Next, as indicated by block 308 in FIG. R,1 and I O,1 and the specified current (I R ) and (I O) of the fundamental harmonic at the determined frequency (f O ) and (f R ) and this factor can be used to correct for the harmonics (V O ) into the electrical line 122, the original measured fundamental or RMS voltage can be calculated, which is done by calculating the square root of the sum of the squared harmonics, and can be shown to the user on the display 312.

[0045] Coupling capacitor (C O ) may generally have a capacitance value in the range of, for example, about 0.02 pF to 1 pF, depending on the distance between the insulated conductor 106 and the conductive sensor 126, as well as the particular shape and dimensions of the sensor 126. B ) may have a capacitance value of, for example, about 20 pF to 200 pF.

[0046] From the above equation (1), the AC reference voltage (V R ) is the signal current (I O ) and reference current (I R ) to achieve a similar current magnitude with respect to the AC voltage (V O ) does not have to be in the same range as the reference frequency (f R ) to select the AC reference voltage (V R ) can be relatively low (e.g., less than 5 V). As an example, the reference frequency (f R ) can be chosen to be 3 kHz, which is the 60 Hz signal frequency (f O ) with a typical 120VRMS AC voltage (V O ) is 50 times higher than the AC reference voltage (V R ) is the signal current (I O ) is the same as the reference current (I R ) can be chosen to be only 2.4V (i.e., 120V divided by 50) to generate the reference frequency (f R ) to the signal frequency (f O) is set to N times the AC reference voltage (V R ) but similar uncertainties are expressed as I R and I O currents (I R ) and (I O ) in the wire 122 to generate an AC voltage (V O ) to have a value that is (1 / N) times larger than the

[0047] Any suitable signal generator may be used to generate a reference frequency (f R ) with an AC reference voltage (V R ) can be generated. In the embodiment shown in FIG. 3, a sigma-delta digital-to-analog converter (Σ-ΔDAC) 310 is used. The Σ-ΔDAC 310 uses the bitstream to generate a defined reference frequency (f R ) and AC reference voltage (V R ) to create a waveform (e.g., a sinusoidal waveform) signal. In at least some embodiments, the Σ-Δ DAC 310 can generate a waveform that is in phase with the window of the FFT 306 to reduce jitter. Any other reference voltage generator, such as a PWM, that may use lower computing power than the Σ-Δ DAC may be used.

[0048] In at least some embodiments, the ADC 302 may have a resolution of 14 bits. In operation, the ADC 302 generates 2x100 ms of ... n The output from the input amplifier 136 may be sampled at a sampling frequency of 10.24 kHz for a nominal 50 Hz signal to provide 10 samples (1024) (10 Hz bins for the FFT 306). For a 60 Hz input signal, the sampling frequency may be, for example, 12.288 kHz to obtain the same number of samples per cycle. The sampling frequency of the ADC 302 is set equal to the reference frequency (f R ) full cycles. For example, the input signal frequency can be in the range of 40 to 70 Hz.O ) depending on the measured frequency of the AC voltage (V O ) bins can be determined using an FFT 306, and a Hanning window function can be used for further calculations to suppress phase shift jitter caused by incomplete signal cycles captured within the aggregation interval.

[0049] In one example, the common mode reference voltage source 130 has a reference frequency (f R ) with an AC reference voltage (V R ) which is between the 40th and 41st harmonics for a 60 Hz signal and between the 48th and 49th harmonics for a 50 Hz signal. The expected AC voltage (V O ) is not a harmonic of the reference frequency (f R ) with an AC reference voltage (V R ) to provide an AC voltage (V O ) is the reference current (I R ) is less likely to affect the measurements.

[0050] In at least some embodiments, the reference frequency (f R ) is the AC voltage in the conductor 122 under test (V O ) is selected to be the frequency that is least likely to be affected by harmonics of the reference current (I R ) exceeds a limit, which may indicate that the conductor 122 is approaching the conductive sensor 126 under test. Measurements (e.g., 100 ms measurements) can be taken with the common mode reference voltage source 130 switched off to detect signal harmonics at several (e.g., three, five) candidate reference frequencies. The AC voltage (V O) Determine the amplitude of the signal harmonics in at that number of candidate reference frequencies and determine which candidate reference frequencies are O) can be identified that is likely to be least affected by signal harmonics of the reference frequency (f R ) can be set to the identified candidate reference frequency. This switching of the reference frequency can avoid or reduce the effect on the effective reference frequency element in the signal spectrum, which may increase the measured reference signal and reduce accuracy, which may result in unstable results. Other frequencies with the same characteristics other than 2419 Hz include, for example, 2344 Hz and 2679 Hz.

[0051] FIG. 5 is a schematic diagram of a sensor subsystem 400 including a sensor array 402. The sensor array 402 can be positioned and operated similarly to the sensor array 126 shown in FIG. 1B and FIG. 2 discussed above. The sensor array 402 can be planar (as shown) or non-planar (e.g., U-shaped, V-shaped). The sensor array 402 includes a first independent sensor array portion having a first plurality of sensor elements 404 ("first sensor portion"). The sensor array 402 also includes a second independent sensor array portion having a second plurality of sensor elements 406 ("second sensor portion"). In at least some embodiments, each of the plurality of sensor elements is elongated in a rectangular shape. In the illustrated example, the sensor elements of the first plurality of sensor elements 404 are interleaved with the sensor elements of the second plurality of sensor elements 406.

[0052] Each of the first plurality of sensor elements 404 is coupled to a node V1, which receives a switch control signal (f synch) 416. Similarly, each of the second plurality of sensor elements 406 is coupled to a node V2 that is alternately coupled to the input voltage signal conditioning circuit 408 and the reference current signal conditioning circuit 410 via switches 412 and 414, respectively. The input voltage signal conditioning circuit 408 couples the processed signal current I O , and the reference current signal conditioning circuit 410 may include processing circuitry configured for the reference current I R The input voltage signal conditioning circuit 408 and the reference current signal conditioning circuit 410 can each include processing circuitry similar to that discussed above (e.g., amplifiers, filters, ADCs, etc.), each specifically configured to measure the voltage input signal and the reference current signal.

[0053] Each of the first and second plurality of sensor elements 404 and 406 can be identically shaped to separate the signal and reference currents prior to the signal conditioning circuitry. This configuration allows for different filters and amplification to be used for the signal and reference currents to optimize signal quality and range for both signals.

[0054] To compensate for any position-dependent imbalance, especially at the edges, the switch control 416 can operate with a 50% duty cycle to alternately couple the first plurality of sensors 404 to the signal current amplifier 408 and the reference current amplifier 410, and alternately couple the second plurality of sensors 406 to the signal current amplifier 408 and the reference current amplifier 410. This has the effect of averaging out local geometric imbalances.

[0055] In at least some embodiments, the signal magnitude of each of the first and second plurality of sensors 404 and 406 is 50% of the signal magnitude compared to a single larger sensor. However, because the signal current and the reference current are processed separately, the signal conditioning circuitry (e.g., gain, frequency) can be advantageously optimized for each specific current.

[0056] In at least some embodiments, the switching frequency (f synch ) can be synchronized to the measurement interval (e.g., 100 ms) to ensure that a full cycle is averaged. For example, the switching frequency is R Or one may choose to switch through a full cycle above twice the reference frequency and at multiples of the reference frequency.

[0057] In at least some embodiments, the first set of sensor elements 404 and the second set of sensor elements 406 are "polled" and the set of sensor elements with the largest signal (e.g., reference current signal, input voltage signal) is used for processing. In at least some embodiments, signals from the two sets are both used equally. In at least some embodiments, a weighted combination of the two sets 404 and 406 may be used linearly or exponentially, or may be otherwise weighted based on the magnitude of each of the signals from the first and second sets of sensor elements.

[0058] As mentioned above, the advantage of directly separating the input voltage signal and the reference current signal is that the accuracy and dynamic range are improved. The gain and frequency bandwidth can be optimized in each of the split signal paths for the low frequency input voltage signal (e.g., 50-60 Hz) and the higher frequency reference current signal (e.g., 2.5 kHz). This feature also reduces noise effects and also reduces the dynamic range required for the ADC. In addition, physically switching the sensor strips as discussed above introduces position effects (on both sides) independent of the position of the conductor under test.

[0059] In at least some embodiments, three or more sensors or sensor arrays can be used to further compensate for the position of the conductor under test (e.g., XY, XYZ). One exemplary application is in a non-contact voltage measurement device that utilizes a hard jaw current clamp, where the position of the conductor under test can be anywhere within the jaws.

[0060] In at least some embodiments of the voltage measurement device disclosed herein, a reference voltage (V R ) is the signal voltage (V O ) caused by the high frequency components of the measured reference current (I R ) can have multiple frequencies to reduce the effect of signal harmonics or interharmonics on the signal voltage (V). For example, a reference voltage source (e.g., voltage source 130 in FIG. 2) can be switched off periodically and FFT frequency bins around the multiple reference frequencies can be analyzed and checked for relative limits. The lowest value is the signal voltage (V O ) or other influencing factors. R ) can be used to define

[0061] In at least some embodiments, switching off the reference voltage source may not necessarily create a gap in the measurement stream. For example, O ) may still be measured when the reference voltage source is switched off, and the reference current (I R ) can be used to estimate the reference current over the interval that the reference voltage source switches off.

[0062] In addition to the reference frequency switching discussed above, other specialized signal characteristics of the reference signal can be used, examples include amplitude or frequency modulation, synchronous or pseudo-stochastic switching, quadrature modulation, phase switching, etc.

[0063] As an example of using a modulated signal, the reference signal may be a modulation frequency f m In at least some embodiments, the modulation frequency f m can be chosen to be exactly an integer number of FFT bins. For example, for an FFT interval of 100 ms, such frequencies are 10 Hz, 20 Hz, 30 Hz, etc. The carrier or reference frequency (f R ) is noiseless, this results in two symmetrical sidebands, one on each side of the reference frequency.

[0064] If both sidebands do not have the same magnitude, then the reference signal (e.g., the signal voltage (V O ) has been jammed. This is a relatively simple identification process that does not require switching off the reference voltage source. If the reference signal is found to be jammed, the system can shift the reference frequency by Δf and check the sidebands again for symmetry until the appropriate (unjammed) reference frequency is identified.

[0065] To further speed up the process, in at least some embodiments, multiple reference frequencies can be used simultaneously. This frequency mixing can be created, for example, by either a predefined table and bit streaming (e.g., ΣΔDAC bit streaming) or analog summation of low-pass filtered outputs of pulse width modulators (PWMs). If PWMs are used, a pair of PWMs can provide the reference frequency and the modulation frequency, and multiple pairs of PWMs can be used to provide multiple reference frequencies and multiple corresponding modulation frequencies.

[0066] In the foregoing detailed description, various embodiments of the devices and / or processes have been described using block diagrams, schematic diagrams, and examples. To the extent that such block diagrams, schematic diagrams, and examples include one or more functions and / or operations, it will be appreciated by those skilled in the art that each function and / or operation within such block diagrams, flow diagrams, or examples can be individually and / or collectively implemented by a wide range of hardware, software, firmware, or substantially any combination thereof. In one embodiment, the subject matter of the present invention may be implemented via an application specific integrated circuit (ASIC). However, those skilled in the art will recognize that the embodiments disclosed herein can be equivalently implemented, in whole or in part, as one or more computer programs running on one or more computers (e.g., as one or more programs running on one or more computer systems), as one or more programs running on one or more controllers (e.g., microcontrollers), as one or more programs running on one or more processors (e.g., microprocessors), as firmware, or substantially any combination thereof, within a standard integrated circuit, and that the circuit design and / or code writing for the software and / or firmware is well within the knowledge of one of ordinary skill in the art in light of the present disclosure.

[0067] Those skilled in the art will appreciate that many of the methods or algorithms described herein may employ additional acts, may omit certain acts, and / or may perform acts in an order other than that specified.

[0068] Moreover, those skilled in the art will recognize that the mechanisms taught herein can be distributed as a program product in a variety of forms, and the exemplary embodiments apply equally regardless of the particular type of signal-bearing medium used to actually effect the distribution, including, but not limited to, the following: floppy disks, hard disk drives, CD-ROMs, digital tape, and recordable forms of media such as computer memory.

[0069] The various embodiments described above may be combined to provide further embodiments, and aspects of the embodiments may be modified, as necessary, to employ systems, circuits, and concepts from the various patents, applications, and publications to provide still further embodiments.

[0070] These and other modifications to the embodiments can be made in light of the above description. Generally, the terms used in the following claims should not be construed to limit the claims to the specific embodiments disclosed in the specification and claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Thus, the claims are not limited by the disclosure.

Claims

1. 1. An apparatus for measuring alternating current (AC) voltage in an insulated conductor, the apparatus comprising: Housing and a sensor subsystem physically coupled to the housing, the sensor subsystem positionable proximate to the insulated conductor, the sensor subsystem comprising a first sensor portion and a second sensor portion separate from the first sensor portion, the sensor subsystem configured to capacitively couple the first sensor portion and the second sensor portion to the insulated conductor; a conductive internal ground guard at least partially surrounding and insulated from the sensor subsystem, the conductive internal ground guard operative to shield the sensor subsystem from stray currents; a conductive reference shield surrounding at least a portion of the housing and insulated from the conductive internal ground guard, the conductive reference shield operative to reduce current between the conductive internal ground guard and an external ground; a common mode reference voltage source that, during operation, generates an alternating current (AC) reference voltage having a reference frequency, the common mode reference voltage source being electrically coupled between the conductive internal ground guard and the conductive reference shield; an input voltage signal conditioning circuit alternately couplable to the first sensor portion and the second sensor portion of the sensor subsystem, the input voltage signal conditioning circuit generating, during operation, a sensor current signal indicative of current conducted through the sensor subsystem due to an input voltage in the insulated conductor under test; a reference signal conditioning circuit alternately couplable to the first sensor portion and the second sensor portion of the sensor subsystem, the reference signal conditioning circuit generating, during operation, a sensor current signal indicative of current conducted through the sensor subsystem due to the AC reference voltage detected in the insulated conductor under test; a control circuit communicatively connected to the input voltage signal conditioning circuit and the reference signal conditioning circuit, wherein during operation, the control circuit: receiving a sensor current signal from each of the input voltage signal conditioning circuit and the reference signal conditioning circuit; determining which of the first sensor portion and the second sensor portion produces a maximum sensor current signal; and a control circuit that determines the AC voltage in the insulated conductor based on the determination which of the first sensor portion and the second sensor portion produces the maximum sensor current signal.

2. 10. The apparatus of claim 1, wherein the first sensor portion comprises a first plurality of spaced apart conductive sensors electrically coupled together and the second sensor portion comprises a second plurality of spaced apart conductive sensors electrically coupled together.

3. The apparatus of claim 2 , wherein the first plurality of conductive sensors of the first sensor portion are interleaved with the second plurality of conductive sensors of the second sensor portion.

4. 2. The apparatus of claim 1, wherein the input voltage signal conditioning circuit is alternately couplable to the first sensor portion and the second sensor portion via a first switch, and the reference signal conditioning circuit is alternately couplable to the first sensor portion and the second sensor portion via a second switch.

5. The control circuit, during operation, synchronously controls the states of the first and second switches to alternately: electrically coupling the first sensor portion to the reference signal conditioning circuit and electrically coupling the second sensor portion to the input voltage signal conditioning circuit; and The apparatus of claim 4 , wherein the second sensor portion is electrically coupled to the reference signal conditioning circuit and the first sensor portion is electrically coupled to the input voltage signal conditioning circuit.

6. 6. The apparatus of claim 5, wherein the control circuit, during operation, synchronously controls the states of the first and second switches with a 50 percent duty cycle.

7. The control circuit, during operation, The apparatus of claim 1 , further comprising: determining the AC voltage in the insulated conductor based on at least the AC reference voltage and the reference frequency.

8. The control circuit, during operation, disregarding the sensor current signals obtained from the first sensor portion and the second sensor portion determined not to produce a maximum sensor current signal; 2. The apparatus of claim 1, further comprising: determining the AC voltage in the insulated conductor based on the sensor current signals obtained from the first sensor portion and the second sensor portion determined to produce the maximum sensor current signal.

9. 1. An apparatus for measuring alternating current (AC) voltage in an insulated conductor, the apparatus comprising: Housing and a sensor subsystem physically coupled to the housing, the sensor subsystem positionable proximate to the insulated conductor, the sensor subsystem comprising a first sensor portion and a second sensor portion separate from the first sensor portion, the sensor subsystem configured to capacitively couple the first sensor portion and the second sensor portion to the insulated conductor; a conductive internal ground guard at least partially surrounding and insulated from the sensor subsystem, the conductive internal ground guard operative to shield the sensor subsystem from stray currents; a conductive reference shield surrounding at least a portion of the housing and insulated from the conductive internal ground guard, the conductive reference shield operative to reduce current between the conductive internal ground guard and an external ground; a common mode reference voltage source that, during operation, generates an alternating current (AC) reference voltage having a reference frequency, the common mode reference voltage source being electrically coupled between the conductive internal ground guard and the conductive reference shield; an input voltage signal conditioning circuit alternately couplable to the first sensor portion and the second sensor portion of the sensor subsystem, the input voltage signal conditioning circuit generating, during operation, a sensor current signal indicative of current conducted through the sensor subsystem due to an input voltage in the insulated conductor under test; a reference signal conditioning circuit alternately couplable to the first sensor portion and the second sensor portion of the sensor subsystem, the reference signal conditioning circuit generating, during operation, a sensor current signal indicative of current conducted through the sensor subsystem due to the AC reference voltage detected in the insulated conductor under test; a control circuit communicatively connected to the input voltage signal conditioning circuit and the reference signal conditioning circuit, wherein during operation, the control circuit: receiving a sensor current signal from each of the input voltage signal conditioning circuit and the reference signal conditioning circuit; determining a weighted combination of the sensor current signals received from the input voltage signal conditioning circuit and the reference signal conditioning circuit; and a control circuit that determines the AC voltage in the insulated conductor based on the weighted combination of the sensor current signals.

10. The apparatus of claim 9 , wherein the weighted combination of the sensor current signals comprises at least one of a linear weighted combination or an exponential weighted combination.

11. 2. The apparatus of claim 1, wherein the input voltage signal conditioning circuitry and the reference signal conditioning circuitry each include at least one of an amplifier, a filter, or an analog-to-digital converter.

12. The apparatus of claim 1 , wherein the sensor subsystem and the conductive internal ground guard each have a non-planar shape.

13. 2. The apparatus of claim 1 , wherein the control circuit takes a first measurement when the common mode reference voltage source is switched off and a second measurement when the common mode reference voltage source is switched on, and determines the AC voltage in the insulated conductor based on at least the first and second measurements.

14. 11. A method of operating an apparatus to measure an alternating current (AC) voltage of an insulated conductor, the apparatus comprising: a housing; a sensor subsystem physically coupled to the housing, the sensor subsystem positionable proximate to the insulated conductor, the sensor subsystem comprising a first sensor portion and a second sensor portion independent of the first sensor portion, the sensor subsystem configured to capacitively couple the first sensor portion and the second sensor portion to the insulated conductor; a conductive internal ground guard at least partially surrounding the sensor subsystem and insulated from the sensor subsystem, the conductive internal ground guard operative to shield the sensor subsystem from stray currents; and a conductive reference shield surrounding at least a portion of the housing and insulated from the conductive internal ground guard, the conductive reference shield operative to reduce current between the conductive internal ground guard and an external ground, the method comprising: causing a common mode reference voltage source to generate an alternating current (AC) reference voltage having a reference frequency, the common mode reference voltage source being electrically coupled between the conductive internal ground guard and the conductive reference shield; generating, via an input voltage signal conditioning circuit alternately electrically coupleable to the first sensor portion and the second sensor portion of the sensor subsystem, a sensor current signal indicative of a current conducted through the sensor subsystem due to an input voltage detected in the insulated conductor under test; generating, via a reference signal conditioning circuit alternately electrically coupleable to the first sensor portion and the second sensor portion of the sensor subsystem, a sensor current signal indicative of a current conducted through the sensor subsystem due to the AC reference voltage detected in the insulated conductor under test; receiving, by a control circuit, the sensor current signal from each of the input voltage signal conditioning circuit and the reference signal conditioning circuit; determining which of the first sensor portion and the second sensor portion produces a maximum sensor current signal; and determining the AC voltage in the insulated conductor based on the determination which of the first sensor portion and the second sensor portion produces the maximum sensor current signal.

15. 1. An apparatus for measuring alternating current (AC) voltage in an insulated conductor, the apparatus comprising: a first sensor portion comprising a first plurality of conductive sensors; a second sensor portion separate from the first sensor portion, the second sensor portion including a second plurality of conductive sensors; an input voltage signal conditioning circuit that generates, during operation, a sensor current signal indicative of a current produced in at least one of the first sensor portion and the second sensor portion due to an input voltage in the insulated conductor under test; a reference signal conditioning circuit that, during operation, generates an AC reference voltage of the device and generates a sensor current signal indicative of a current generated in at least one of the first sensor portion and the second sensor portion due to the AC reference voltage sensed in the insulated conductor under test; a first controllable switch operative to alternately couple each of the first sensor portion and the second sensor portion to the input voltage signal conditioning circuit; a second controllable switch operative to alternately couple each of the first sensor portion and the second sensor portion to the reference signal conditioning circuit; a control circuit communicatively connected to the input voltage signal conditioning circuit, the reference signal conditioning circuit, the first controllable switch, and the second controllable switch, wherein during operation, the control circuit: Controlling the first controllable switch to alternately couple the first sensor portion to the input voltage signal conditioning circuit and the second sensor portion to the input voltage signal conditioning circuit; controlling the second controllable switch to alternately couple the first sensor portion to the reference signal conditioning circuit and to alternately couple the second sensor portion to the reference signal conditioning circuit; receiving a sensor current signal from each of the input voltage signal conditioning circuit and the reference signal conditioning circuit; determining which of the first sensor portion and the second sensor portion produces a maximum sensor current signal; and a control circuit that determines the AC voltage in the insulated conductor based on the determination which of the first sensor portion and the second sensor portion produces the maximum sensor current signal.

16. 16. The apparatus of claim 15, wherein the first sensor portion comprises a first plurality of spaced apart conductive sensors electrically coupled together and the second sensor portion comprises a second plurality of spaced apart conductive sensors electrically coupled together.

17. 17. The apparatus of claim 16, wherein the first plurality of conductive sensors of the first sensor portion are interleaved with the second plurality of conductive sensors of the second sensor portion.

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