Abstract: A transformer testing device (10) comprises outputs (31-33) for detachably connecting the transformer testing device to windings of multiple phases of a transformer (50). The transformer testing device (10) further comprises a plurality of sources (21-23), each of which is designed to generate a test signal. The transformer testing device (10) also comprises a switching matrix (40) that is connected between the plurality of sources (21-23) and the outputs (31-33).

Abstract: A detection method and system are provided to detect an arc fault signal in a (HF) high frequency signal monitored on a power line. The HF signal is monitored on the power line over a predefined time period such as a half-cycle of a base frequency, and is partitioned into a plurality of smaller time-segmented signal segments over the period. For each signal segment, a first filter is applied to a signal spectrum of the signal segment to produce a filtered signal spectrum having one or more frequency intervals associated with power line communication filtered from the signal spectrum. HF signal content is checked in the filtered signal spectrum, and a binary value is assigned to the signal segment based upon a presence or absence of HF signal content. Thereafter, an arc fault event is determined based on the accumulated binary values of the signal segments.

Abstract: A measurement circuit may include a transistor having a first terminal, a second terminal, and a third terminal, wherein the first terminal is coupled to a first reference voltage. The measurement circuit may further include a first operational amplifier including a first input coupled to the second terminal of the transistor and an output coupled to the third terminal of the transistor. The first operational amplifier may further include a second input configured to receive a second reference voltage. The measurement circuit may also include a first unity-gain voltage follower including a second operational amplifier having a first input coupled to the first input of the first operational amplifier. Methods of measuring a threshold voltage, semiconductor devices, and electronic systems are also described.

Abstract: An aging test method for a light emitting device is provided. The aging test method includes: collecting, in an aging process applied to the light emitting device, an initial value of a first characteristic parameter of the light emitting device and an initial test time point; collecting a current value of the first characteristic parameter and a current test time point (step S1); generating a feature line according to the initial value, the current value, the initial test time point, and the current test time point, and calculating a slope of the feature line; determining whether the slope of the feature line is greater than or equal to a predetermined threshold and less than 0, and returning to the step S1 if a result of the determination is NO; and terminating the aging process applied to the light emitting device if the result of the determination is YES.

Abstract: The present invention relates to a test system for testing a device under test, comprising a signal generating unit being connectable to an input node of the device under test and being adapted to generate a test signal to be applied to the input node of the device under test, wherein the test signal comprises a plurality of frequency peaks at different frequencies. A receiving unit is connectable to an output node of the device under test and is adapted to receive a response signal from the device under test in response to the test signal. An analyzing unit for analyzing the device under test is adapted to determine at least one of a gain value and a phase value based on the test signal generated by the signal generating unit and the response signal received by the receiving unit.

Abstract: A test circuit includes a test pad supplied with a test signal causing the test circuit to be transitioned to a test mode, and further includes a first p channel MOS transistor having a source connected to the test pad, and a gate applied with a prescribed reference voltage, a first n channel MOS transistor having a drain connected to a drain of the first p channel MOS transistor, and a source grounded via a first current limiting element, and a control circuit which has an input terminal connected to the drain of the first n channel MOS transistor, and an output terminal connected to a gate of the first n Tr, and controls the first n channel MOS transistor from an on state to an off state when the test signal becomes a prescribed voltage or more.

Abstract: An automated test equipment (ATE) system comprises a system controller, wherein the system controller is communicatively coupled to a tester processor and an FPGA. The FPGA is communicatively coupled to the tester processor, wherein the FPGA is configured to internally generate commands and data transparently from the tester processor for testing a DUT. Further, the system comprises a demultiplexer positioned between the DUT and the FPGA, wherein, responsive to a determination that the DUT is operating in a high speed mode, the demultiplexer is configured to channel data traffic from the DUT to a Serializer/Deserializer (SerDes) receiver on the FPGA, and further wherein, responsive to a determination that the DUT is operating in a low speed mode, the demultiplexer is configured to channel data traffic from the DUT to input buffers on the FPGA with switchable on/off input terminations.

Abstract: The present disclosure provides a testing method and a testing system. The testing method is performed by at least one processor and includes the following operations: converting a circuit data of a scan test to a program, in which the program is configured to observe an untested part of a circuitry that is unable to be tested in the scan test; generating a waveform data associated with the untested part; generating a look-up table according to the program and a netlist file, in which the netlist file indicates the circuitry; and testing the untested part of the circuitry according to the waveform data and the look-up table.

Abstract: A test mode set circuit includes: a first test mode set block suitable for setting entry into a first test mode based on a clock signal and first data outputted from a non-volatile memory during a first period of a boot-up operation; and a second test mode set block suitable for setting entry into a second test mode based on the first data and second data outputted from the non-volatile memory during a second period of the boot-up operation, or setting entry into the second test mode based on a set signal generated by a combination of a command and an address during a normal operation.

Abstract: The present invention discloses a method and an apparatus for processing data of a multifunctional automobile charger by using a microprocessor. A main program module, an ignition current detection module, a charging current detection module, an internal battery constant current charging detection module, an internal battery temperature detection module, an output current detection module, a wireless charging failure detection module, a module for Bluetooth communication with a mobile phone and so on are loaded in a single chip microcomputer. Instructions of the modules are executed by a processor. The present invention provides an ignition function for an automobile, can communicate with a mobile phone, and is convenient to use.

Abstract: Certain embodiments provide battery system including: a battery; a current measurement unit configured to measure a current charged to or discharged from the battery; a voltage measurement unit configured to measure an output voltage of the battery; a function creation unit configured to create a function representing a depth-of-discharge characteristic of the battery on the basis of the measured current and output voltage; and a remaining capacity calculation unit configured to calculate a remaining capacity corresponding to the output voltage of the battery using the created function.

Abstract: A battery system monitor includes cell measurement circuits (CMCs) that each measure a voltage at or current through a pair of terminals of a respective associated battery module from among a plurality of plurality of battery modules in a battery system. Wireless communication transceivers (WCTs), each associated with a different CMC, transmit voltage or current measurement information of the associated CMC across a wireless communication link. A controller receives the voltage or current measurement information from the wireless communication transceivers for monitoring the state of operation of the battery system. Battery system monitoring is improved through synchronization of clocks in different CMCs or WCTs to enable synchronous sampling of multiple battery modules, through systems for determining relative positions of battery modules in a series coupling of battery modules between terminals of the battery system, and through improvements to the reliability of wireless communication.

Abstract: Example implementations relate to performance tests of capacitors. In some examples, a controller may comprise a processing resource to measure a change in voltage of a capacitor of a circuit in response to the controller entering a test mode, determine, based on the measured change in the voltage and an impedance of the circuit, a capacitance of the capacitor, compare the determined capacitance of the capacitor to a predetermined capacitance value, and determine, based on the comparison, a performance of the capacitor.

Abstract: A test system for testing electrical connections, especially soldered connections, between electronic components and a circuit board to be tested, characterized in that the test system has a communication interface, which by contacting the circuit board enables a data exchange with a data memory or a communication module of the circuit board to be tested, wherein the communication interface is arranged within a housing of the test system freely movably in at least two spatial directions, preferably three spatial directions.

Abstract: A linearity compensation circuit is disclosed for improving the linearity of a sensing signal. The linearity compensation circuit may include a compensator that is capable of receiving a sensing signal from a sensor and generating a compensation signal based on the sensing signal. The linearity compensation circuit may also include an output circuit that is capable of combining the compensation signal and the sensing signal to generate a compensated signal that exhibits an improved linearity. Also disclosed is a sensing apparatus which includes a sensor and the linearity compensation circuit. The sensing apparatus may thus be able to generate a sensing signal that is linear over a wider dynamic range.

Abstract: Systems and methods are disclosed for automatically calibrating a magnetometer during user activity. A portable device associated with a user provides magnetic field measurements during user activity, which are converted to a frequency domain and frequency component(s) that correspond to the user activity are distinguished. A criterion is defined for the distinguished frequency components such that magnetometer bias is estimated by satisfying a condition for the criterion. Accordingly, the estimated magnetometer bias may be applied to the obtained magnetic field measurements. The calibrated magnetic field measurements may be used for any suitable purposes, including for building a magnetic fingerprint map using crowdsourcing techniques.

Abstract: A measuring apparatus that measures a measurement target amount generated from a measurement target, includes an additional amount generating section, a sensor, and a deriving section. The additional amount generating section generates an additional amount to be added to the measurement target amount. The sensor measures a composite amount of the measurement target amount added with the additional amount. The deriving section derives the measurement target amount from an output of the sensor. The additional amount is a pulse. The pulse has an amplitude higher than the absolute value of the maximum of the measurement target amount. The maximum of the pulse is zero. The pulse has a frequency high enough to ignore the 1/f noise. The deriving section detects the output value of the sensor to derive the measurement target amount.

Abstract: A circuit has a magnetic sensor that produces an uncompensated magnetic sensor output signal. A temperature sensor produces an ambient temperature signal. A compensation circuit is connected to the magnetic sensor and the temperature sensor. The compensation circuit is configured to add a computed temperature compensation signal to the uncompensated magnetic sensor output signal to produce a magnetic sensor temperature compensated output signal that reduces thermally induced variation of the uncompensated magnetic sensor output signal.

Abstract: An electromagnetic sensing device with a package substrate, a first die mounted on the package substrate, and a second die mounted on the package substrate. The first die includes a first integrated circuit and a first magnetic core formed above the first integrated circuit. The first magnetic core has a first sensing axis parallel to a planar surface of the package substrate. The second die includes a second integrated circuit and a second magnetic core formed above the second integrated circuit. The second magnetic core has a second sensing axis orthogonal to the planar surface of the package substrate.

Abstract: Methods and apparatus for a sensor having non-ratiometric fault trip level setting. In embodiments, a sensor has a sensing element with a fixed gain. A signal processing module receives the fault trip level setting and maintains the fault trip level setting constant during changes in the supply voltage.

Abstract: A method for estimating a coil sensitivity map for a magnetic resonance (MR) image includes providing a matrix A of sliding blocks of a 3D image of coil calibration data, calculating a left singular matrix V? from a singular value decomposition of A corresponding to ? leading singular values, calculating P=V?V?H, calculating a matrix that is an inverse Fourier transform of a zero-padded matrix P, and solving MHcr=(Sr)Hcr for cr, where cr is a vector of coil sensitivity maps for all coils at spatial location r, and M = ( ( 1 1 … 1 0 0 … 0 … … … 0 0 … 0 ) ? ( 0 0 … 0 1 1 … 1 … … … 0 0 … 0 ) ? ? … ? ? ( 0 0 … 0 0 0 … 0 … … … 1 1 … 1 ) ) .

Abstract: A rotor contains a sample. A turbine cap is fitted into an opening of one end of the rotor, and a bottom cap is fitted into an opening of the other end of the rotor. A recess portion is formed in the turbine cap, and a recess portion is formed in the bottom cap. Insert members having a negative linear expansion coefficient are disposed in the recess portions.

Abstract: Technologies relating to a magnetic resonance spectrometer are disclosed. The magnetic resonance spectrometer may include a doped nanostructured crystal. By nanostructuring the surface of the crystal, the sensor-sample contact area of the crystal can be increased. As a result of the increased sensor-sample contact area, the output fluorescence signal emitted from the crystal is also increased, with corresponding reductions in measurement acquisition time and requisite sample volumes.

Abstract: In a method, device and digital receiver for transmitting signals in magnetic resonance imaging, M channels of digital signals are received over M receiving channels from a digital matrix processor. One receiving channel corresponds to one channel of digital signal and the M channels of digital signals include one channel of main signal and (M?1) channels of high-order signals. The M channels of digital signals are combined into N channels of combined signals, wherein the main signal and at least one channel of high-order signal are combined into one channel of combined signal, or at least two channels of high-order signals are combined into one channel of combined signal. N and M are both positive integers, N is less than M, and M is greater than or equal to 2.

Abstract: A method is provided for magnetic resonance (MR) imaging near metal, including acquiring an image at a first magnetic field from a subject that includes a metal object, acquiring an image at a second magnetic field, and combining the images to provide a corrected image with reduced metal distortion. An MR imaging system for measuring near metal is also provided including a superconducting magnet to provide a magnetic field, a power supply for a current to ramp the magnetic field, a cryocooler in contact with the superconducting magnet, a magnetic field controller programmed to ramp the main magnetic field by adjusting the current generated by the power supply, a radio frequency system for transmitting and receiving signals, and a data aquisition and processing system to receive the MR signals, generate image data sets and combine the image data sets to provide a corrected image having a reduced metal distortion.

Abstract: Disclosed herein are systems and methods involving the use of magnetic resonance imaging and optogenetic neural stimulation. Aspects of the disclosure include modifying a target neural cell population in a first region of a brain to express light-responsive molecules. Using a light pulse, the light-responsive molecules in the target neural cell population are stimulated. Multiple regions of the brain are scanned via magnetic resonance imaging. The scans allow for observation of a neural reaction in response to the stimulation in at least one of the multiple regions of the brain.

Abstract: A medical image diagnosis supporting apparatus includes a quantitative value reception unit that receives data of kinds of quantitative values obtained in advance at points in a region of a subject; a variable conversion unit that calculates kinds of intermediate information values dependent on the kinds of quantitative values at each of the points using the kinds of quantitative values at each of the points and kinds of variable conversion functions; and a diagnosis image calculation unit that calculates a diagnosis image for the region. The diagnosis image calculation unit sets a pixel value at each of the points in accordance with a combination of kinds of intermediate information values obtained at each of the points by the variable conversion unit or a combination of intermediate information values and kinds of quantitative values at the point and generates the diagnosis image.

Abstract: A signal error calibrating method is disclosed herein and includes following steps: filtering an error voltage in a sensor by a low pass filter in a calibration mode; converting the offset voltage to be a digital offset signal by an analog digital signal converter; converting the digital offset signal to be an offset calibrating signal by a digital analog signal converter; transmitting the offset calibrating signal to an input end of the sensor so as to offset an error voltage at the input end of the sensor. After calibrating the error voltage, the analog digital converter in the error calibrating circuit can be used for the need of signal output and the low pass filter is turned off at the same time.

Abstract: A method for dynamically compensating for the offset error of an acquisition system includes a current sensor to measure or estimate the current passing through an actuator of a electrical apparatus that is electrically supplied by an AC voltage, the acquisition system having a predetermined offset value, the method includes determining a plurality of periodic temporal operating ranges of the actuator in order to dynamically apply a compensation sequence for the offset error of the acquisition system, executing the compensation sequence during any one among the plurality of determined temporal operating ranges, the synchronization between the any one of the determined temporal operating ranges of the actuator and the execution of the compensation sequence being performed using a synchronization system including a synchronization module designed to identify reference times from the AC supply voltage of the sector.

Abstract: A point stick module has a sensing device, a rank unit and a signal processing device. The sensing device outputs multiple sensing signals in response to operations done by a user. The rank unit provides a rank signal to represent a rank of the sensing device. The signal processing device is coupled to the sensing device and the rank unit to receive the multiple sensing signals and the rank signal, wherein the signal processing device selects a parameter according to the rank signal.

Abstract: The present disclosure relates to generating a measurement sensor profiling summary in relation to a measurement sensor of an electrical measurement system, the measurement sensor being suitable for measuring an electrical property. The profiling summary is generated by obtaining a plurality of profiling results each comprising an estimate of a transfer function of a measurement sensor of the electrical measurement system and a corresponding certainty value indicative of the accuracy of the estimate of the transfer function, wherein the plurality of profiling results are based on estimates of the transfer function of the measurement sensor and corresponding certainty values that were determined by a monitor module of the electrical measurement system during a profiling period of time; and generating a profiling summary based on at least one of the plurality of profiling results.

Abstract: An apparatus that includes a phased array configured to monitor a broad bandwidth with low rate ADC achieving sub-Nyquist rate sampling with 100 percent duty cycle. The phased array includes a plurality of phased array elements. Each of the phased array elements are inserted with a non-uniform true time delay to enable simultaneous measurement of an AOA and a frequency of an incident RF signal.

Abstract: An apparatus for providing marine information is provided including a user interface, a processor, and a memory including computer program code. The memory and the computer program code are configured to, with the processor, cause the apparatus to generate a sonar image based on sonar return data received from an underwater environment, determine a location associated with the sonar return data based on location data received from one or more position sensors, and render a nautical chart on a display. The computer program code is further configured to cause the apparatus to receive a user input on the user interface directed to a portion of the display in which the nautical chart is presented, and modify presentation of the nautical chart such that the portion of the display presents the sonar image in response to receiving the user input.

Abstract: A source of a sound is located by two or more computing devices (e.g., A/V recording and communication devices) using microphones and radio frequency communication among the computing devices. The location of the source is determined based on at least a time difference between a time that a notification from a first computing device regarding the sound arrives at a second computing device, and a time of detecting the sound at the second computing device. Additional data may be collected and/or other actions may be taken in response to locating the source of the sound.

Abstract: The present invention relates to a method for locating sources emitting electromagnetic pulses, each source belonging to a carrier platform, the method comprising the following steps: receiving, by a detector, for each source to be located, at least one same emitted pulse, received directly and received by reflection on the carrier platform of another source, measuring the arrival direction, the arrival date and at least one invariant characteristic of each received pulse. The method further comprises the following steps: grouping together a first pair of pulses and a second pair of pulses, calculating the difference of dates of arrival between the pulses of each pair, determining the direction and the distance of each source from the detector from calculated differences of dates of arrival of the pulses of each pair.

Abstract: An illustrative example method of tracking a detected object comprises determining that a tracked object is near a host vehicle, determining an estimated velocity of the tracked object, and classifying the tracked object as frozen relative to stationary ground when the estimated velocity is below a preselected object threshold and a speed of the host vehicle is below a preselected host threshold.

Abstract: A method for a device for determining the location of a mobile transmitting device using a two phase time difference of arrival method and to a system using such a device are presented. There is a first radio node for calculating a location of a third radio node, for receiving, from the third radio node, a first ranging signal and for calculating, based on the first ranging signal, a first ranging parameter. The first radio node receives, from a second radio node, a second ranging signal, transmits to the second radio node a third ranging signal, calculates a phase offset between the first and second radio nodes based on the second and third ranging signals, and calculates a distance between the first and third radio nodes based on the phase offset between the first and second radio nodes based on the first ranging parameter.

Abstract: In one embodiment, a method includes accessing an operational status of a vehicle that is coupled to a radar antenna array, accessing sensor data that includes a count of and a location of a plurality of objects within a vicinity of the vehicle, accessing signal strength data associated with one or more base station antennas located within the vicinity of the vehicle, and determining to switch at least some of a plurality of radar resources of the radar antenna array from an object detection mode to a data transfer mode. The determination is based on the operational status, the sensor data, or the signal strength data.

Abstract: Disclosed is a method and apparatus for detecting an object using a radar in a vehicle, wherein object detection is performed by generating a transmission signal using a code sequence, receiving an echo signal reflected from an object, and detecting the object based on the echo signal and the code sequence.

Abstract: A three-dimensional (3D) sensor device achieves accurate distance measurements in the presence of multipath illumination interference (MPII) by estimating the effect of indirect illumination on a given pixel's optical signal measurement and correcting the signal measurement to remove the estimated contribution from indirect illumination. After generating an initial point cloud image of a scene, the sensor device identifies target objects and background objects within the scene, where the background objects are potential sources of indirect illumination. The sensor device estimates the total amount of indirect illumination directed to a point on the target object by the background objects and received at a pixel corresponding to the point, and corrects the measured signal at the pixel to remove the contribution of this estimated indirect illumination.

Abstract: An angle-resolving FMCW radar sensor, including multiple antenna elements in positions in a direction in which the radar sensor is angle-resolving and forming at least three transmitter arrays and at least one receiver array, and a control/evaluation device for an operating mode in which transmitter arrays periodically transmit signals whose frequency is modulated according to modulation ramps, and in which radar echoes of transmitted signals are received in by multiple antenna elements of the receiver array, and the located object angle is determined based on amplitude and/or phase relationships between radar echoes which correspond to different combinations of transmitter and receiver arrays. A measuring cycle of the radar sensor includes at least two periods in which in each case at least two combinations of transmitter and receiver arrays are alternated, and the combinations of transmitter and receiver arrays involved are different from one another for the at least two periods.

Abstract: A method of mitigating vibration in a radar system on a moving platform includes obtaining received signals resulting from reflections of transmitted signals by one or more objects in a field of view of the radar system. The received signals are a three-dimensional data cube. The method also includes processing the received signals to obtain a first three-dimensional map and second three-dimensional map, estimating the vibration based on performing a first detection using the second three-dimensional map, and cancelling the vibration from the first three-dimensional map to obtain a corrected first three-dimensional map. A corrected second three-dimensional map is obtained by further processing the corrected first three-dimensional map; and a second detection is performed using the corrected second three-dimensional map.

Abstract: A sensor assembly includes a first body that rotates a sensor component about an axis, and a second body coupled to the first body to form a separation gap. The separation gap extends radially inward from a gap inlet to a sealed barrier of the second body. The separation gap may be configured with a set of air guide structural features, to induce formation of eddies from air intake received through the gap inlet, as air from the air intake moves inward towards the sealed barrier.

Abstract: A lidar system includes a light source to generate a frequency modulated continuous wave (FMCW) signal, and a waveguide splitter to split the FMCW signal into an output signal and a local oscillator (LO) signal. A transmit coupler provides the output signal for transmission. A receive lens obtains a received signal resulting from reflection of the output signal by a target. A waveguide coupler combines the received signal and the LO signal into a first combined signal and a second combined signal. A first phase modulator and second phase modulator respectively adjust a phase of the first combined signal and the second combined signal to provide a first phase modulated signal and a second phase modulated signal to a first photodetector and a second photodetector. A processor processes a first electrical signal and a second electrical signal from the first and second photodetectors to obtain information about the target.

Abstract: A chip-scale lidar system includes a first light source to output a first signal, and a second light source to output a second signal. A transmit beam coupler provides an output signal for transmission that includes a portion of the first signal and a portion of the second signal, and receive beam coupler obtains a received signal resulting from reflection of the output signal by a target. The system includes a first and second set of photodetectors to obtain a first and second set of electrical currents from a first and second set of combined signals including a first and second portion of the received signal. A processor obtains Doppler information about the target from the second set of electrical currents and obtains range information about the target from the first set of electrical currents and the second set of electrical currents.

Abstract: Aspects of the present disclosure relate to systems and methods for time-of-flight ranging. An example time-of-flight system includes a transmitter including a plurality of light emitters for transmitting focused light, the plurality of light emitters including a first group of light emitters for transmitting focused light with a first field of transmission and a second group of light emitters for transmitting focused light with a second field of transmission. The first field of transmission at a depth from the transmitter is larger than the second field of transmission at the depth from the transmitter. The time-of-flight system also includes a receiver to receive reflections of the transmitted light.

Abstract: A lidar system can be used to measure a distance to one or more objects in a target region, such as by transmitting light towards the target and then receiving light reflected or scattered from the target. Received light can be stored as charge on storage elements such as capacitors, where received light can be stored on different storage elements depending on a time of arrival of the received light. A reduction in the number of storage elements can be achieved by providing one or more groups of storage elements, where each group of storage elements can correspond to a digit of a time of flight, where the time of flight can be round trip travel time of a light beam travelling from the lidar system to the target region and then back to the lidar system. Each group of storage elements can be arranged in a binary tree of a decimal tree configuration.

Abstract: A method includes generating a transmit beam in different intervals of time and directing the transmit beam towards an area or object of interest. The method also includes receiving a receive beam that includes the transmit beam as reflected from the area or object of interest. The method further includes generating local oscillator (LO) laser light. The transmit beam and the LO laser light are frequency-shifted such that the transmit beam has a higher frequency than the LO laser light in a first subset of the intervals and a lower frequency than the LO laser light in a second subset of the intervals. In addition, the method includes processing the LO laser light and the receive beam to identify information about the area or object of interest.

Abstract: An ultrasound imaging system with pixel oriented processing is provided in which a method of producing a Doppler velocity image is accomplished by emitting unfocused acoustic signals into a medium over substantially an entire field; receiving scattered and reflected ultrasonic signals on a transducer array in response to the emission; processing the received ultrasonic signals to extract information to construct a Doppler velocity signal corresponding to at least one point in the medium; and generating on a display device the Doppler velocity image from the processed Doppler velocity signal. Acquisition sequences and signal processing algorithms are described that provide improved quantification of fluid flow parameters, including improved discrimination between regions of blood flow and tissue. Very high frame rate Spectral Doppler and Vector Doppler acquisition modes for real-time and post-acquisition visualization over a large field of view are described.

Abstract: An electronic device includes a first portion, a second portion, and a joint moveably coupling the first and second portions for angular adjustment between the first and second portions. A speaker is fixed on the first portion at a first known distance from the joint, and a microphone is fixed on the second portion at a second known distance from the joint. An angle sensing machine is configured to emit a known sound from the speaker, detect the known sound at the microphone, and measure a transmission time of the known sound from speaker to microphone. Based on the transmission time, a current angle of the first portion relative to the second portion is calculated.