Crystal Instruments Corporation

Chrystal Instruments Corporation

Sentek Dynamics Inc.

James Q Zhuge

Zhengge Tang

Weijie Zhao

Lei Chen

Andrew P Snyder

Yihao Liu

Michael Nichols

Aakash Umesh Mange

Hongjian Gao

A measurement system has a data acquisition architecture in one or more channels with storage in multiple sensor ranges. At least one sensor channel provides an analog measurement input signal, which is split into first and second amplifier-ADC paths, where a first path has relatively higher gain and smaller range than a second path. The digitized data is subject to cross-channel calibration that can serve as a trigger for the transfer of the two data streams into nonvolatile memory. The incoming data are temporarily stored for a specified period in a circular buffer, so that the trigger can also facilitate transfer of pre-trigger data from the buffer into the memory. A processor determines the presence or absence of any clipping of the higher-gain/smaller-range data and selects analysis of that smaller range data if no clipping is detected, but of the larger range data if clipping is detected.

Data recording based on dual ADC architecture

Sensors outside of a control loop are used in a single axis electrodynamic shaker where an armature exerts variable amounts of vibration with a single degree of freedom on a test unit affixed to a support table. The sensors are remote from the test unit, such as laser sensors measuring movement of the test unit. Typically an array of such shakers move a support table having an affixed test unit. A controller uses inputs from the remote sensors to signal warnings of overturning moments of the support table that can damage the armatures or to shut down.

Safety apparatus for one degree of freedom electrodynamic shaker

A distributed data acquisition system comprising multiple, physically unconnected, data acquisition units that can be in wireless communication with a remote host, timestamps measurement data with sub-microsecond time base accuracy of sampling clock relative to an absolute timeframe. Each unit has a GPS receiver for deriving an absolute time. An analog-to-digital converter samples measurement data using a sampling clock. A hardware logic circuit, such as a field programmable gate array, associates batches of the measurement data with corresponding timestamps representing the current absolute time. A time offset bias may be compensated by a comparison of timestamps with nominal time based on start time and nominal sampling rate. Additionally, the sampling clock may be synchronized using time pulses from the GPS receiver. An initial start of ADC sampling by all data acquisition units may be also synchronized.

Sampling synchronization through GPS signals

For cross-channel spectral analysis of measurement data from multiple recording units with independent sampling clocks, a processing method corrects phase mismatch between the data received over the different channels. Blocks of sampled measurement data are buffered in a hardware logic circuit and timestamps are associated with successive blocks through a hardware interrupt to a GPS receiver of each recording unit. For each first channel data block, the block's starting point, a closest point in time in a data block of the second channel, and the starting point of that second channel data block are determined, using GPS timestamps associated with those data blocks, nominal sampling rate and block size. Phase correction based on the time offset between starting points of the pairs of data blocks and the interval between starting points of successive blocks is applied in the frequency domain after a time-to-frequency domain transformation. Multiple frames of phase-corrected spectra may then be averaged. Only a subset of samples in each data block need be used based upon a specified overlap ratio.

Cross spectrum analysis for time stamped signals

A method uses a distributed data acquisition system with multiple, physically unconnected, data acquisition units, that can be in wireless communication with a remote host, to timestamp measurement data with sub-microsecond time base accuracy of sampling clock relative to an absolute timeframe. A current absolute time is derived from messages received from a satellite radio beacon positioning system (GPS). Measurement data is sampled by each unit at a specified sampling rate. Using hardware logic, batches of sampled data are associated with corresponding timestamps representing the absolute time at which the data was sampled. Data and timestamps may be transmitted to the host. A time offset bias is compensated by comparing timestamps against a nominal time based on start time and nominal sampling rate. The sampling clock rate may be disciplined using time pulses from the GPS receiver. An initial start of data sampling by all units can also be synchronized.

A vibration testing system for structures visually displays vibration analysis information in the form of a graphic animation using a 3D model of the object. While only a subset of the surface points of the object model correspond to sensors on the structure, an interpolation feature of the system allows deformation information for all points of the model to be estimated. Interpolation weights can be calculated in advance to allow for real-time display of a test. Color can be used to enhance visualization of vibration amplitudes. The visualization can be performed offline after a vibration test has been completed to show modal analysis results or can be done in real-time using either blocks or RMS data obtained while the vibration testing is still on-going. This is especially useful for adjusting test parameters, such as the excitation location, amplitude or both, for more effective testing.

Vibration visualization with real-time and interpolation features

A modal vibration analysis system and corresponding method is provided. Exciters are coupled to a structure under test for generating vibrations in the structure. Sensors are coupled to the structure at multiple locations for sensing vibrations generated in response to the excitations. A controller provides drive signals to the exciters such that the sensor signals have a target output spectrum with specified characteristics in multiple designated frequency domains of the spectrum, characterized by a random phase for each frequency. Modal analysis processes digitized sensor signals with a Fast Fourier Transform conducted at two or more specified data sampling rates to synthesize a spectrum containing data points with finer frequency resolution for lower frequency range, and regular frequency resolution for higher frequency range. From the multi-resolution spectra, natural frequencies and damping coefficients are determined at each mode, and a mode shape at each natural frequency is computed.

Modal vibration analysis system

A plurality of measurement devices have analog sensors that measure the dynamic signals of physical events, sample the data into digital format with time synchronized clocks and generate time stamped Ethernet messages that are sent to a remote host. The remote host has a master clock that evaluates decoded time stamped messages from the measurement devices and sends back a message with a time correction error signal relative to the master clock. This feedback signal is used by the measurement devices to correct a local clock for data sampling and new message generation. Eight wire cable and associated connectors are used to handle three channels of traffic, with four wires dedicated to Ethernet messages as one channel, another two wires dedicated to reset and other commands as a second channel and another two wires to transmit power from the host to the measurement devices as a third channel.

Synchronized measurement device using local area network with ethernet messaging

A shaker test apparatus is provided along with a method of collecting and processing images, wherein a shaker table is driving the device under test by a vibration controller at a known vibration frequency and period, wherein a device under test obtains a steady-state vibration characteristic of that excitation frequency when mounted on the shaker table. While the device under test is being excited, a trigger signal controller triggers a camera to capture a series of still image frames at a regular sampling frequency that is less than the vibration frequency (under-sampling), and a timer associated with the camera records a timestamp of an image capture time for each image frame. A computer processor uses the timestamps to remap the order of the image frames, shifting each frame's capture time backwards by a specified multiple of vibration periods in order to correctly represent a single vibration period beginning with an earliest captured image.

Vibration image acquisition and processing

In a data acquisition instrument with dual A/D converters in each measurement channel, phase corrections between the paths are computed using a locally generated calibration signal. The calibration signal goes through dual paths simultaneously and is stitched into a single signal for analysis by a processor running a Fourier transform where phase differences are easily identified and used to establish a phase correction signal applied to a single master clock supplying clock signals to both paths. A switch allows the calibration signal to be applied to each channel or to no channels when actual data is being collected.

Cross-path phase calibration for high dynamic range data acquisition

A control method for a mechanical vibration system independently modifies the higher and lower frequency components of the drive signal satisfying a target profile in a manner that limits displacement in the driven vibration. In particular, phases of the lower frequency components in a preliminary drive spectrum are independently adjusted so that peaks of the respective components are non-simultaneous and distributed in time to avoid contributing constructively. For example, the lower frequency components may be applied as a filter to a narrow-band time waveform, such as one with a swept frequency, to obtain the lower-frequency time waveform. The higher frequency components are randomized in their phase, transformed into the time domain, and recombined with the lower frequency part to obtain the drive signal.

Mechanical vibration system and control method with limited displacement

The present invention utilizes multiple A/D (analog-to-digital) paths and cross-path calibration to provide accurate and reliable measurements for each input channel in a data acquisition system. When the system and method are applied, user and automated methods of selecting among a number of alternative input range settings can be reduced, or even eliminated. That is, there is a significant reduction or complete elimination of input range settings in a measurement system. For each measurement channel of interest, the input signal is directed to at least two paths, e.g., Path A and Path B. The first path measures the full range (e.g., +/&#x2212;10 volts), while the second path includes a high-gain amplifier. Each path includes an analog-to-digital converter (ADC), so that there is a one-to-one correspondence between the number of paths and the number of ADCs, which sample the input signal simultaneously.

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Palo Alto, CA, United States of America

James Q Zhuge