)The process of obtaining a sequence of instantaneous values of a function at regular or intermittent intervals.
The frequency, in samples-per-second, at which analog signals are sampled and then digitized. The inverse of the sampling interval (See NYQUIST FREQUENCY).
The time between samples in a sampled data system;
where:
Shannon's sampling theorem states that for a bandlimited signal, slightly more than two samples per period of the bandlimiting frequency are required to completely reconstruct the continuous signal from its samples. In sampled data systems, the sampling rate must be greater than two times the highest frequency present in the data, to be analyzed without aliasing.
See CALIBRATION FACTOR.
SINGLE DEGREE OF FREEDOM (See DEGREES OF FREEDOM).
The maximum responses of a series of uniformly damped single-degree-of-freedom (SDOF) systems to an applied transient waveform, plotted as a function of the natural frequencies of the SDOF systems.
Primary SRS Maximum responses are determined during the application of the non-zero input waveform.
Residual SRS Maximum responses are determined during the period after the input waveform has been removed.
Maximum (Maximax) SRS Maximum responses are determined from the maximum values of both the primary and the residual SRS.
Acceleration SRS Maximum responses are measured in acceleration units.
Velocity SRS Maximum responses are measured in velocity units.
Displacement SRS Maximum responses are measured in displacement units.
A secondary response separated by a notch from the main or desired response. Usually refers to a filter spectral shape, particularly in digital filters that have complex structure (many notches and peaks) in the filter transition band (See FILTER, DIGITAL).
Process of extracting information about a signal's behavior in the time domain and/or frequency domain. Describes the entire process of filtering, sampling, digitizing, computation, and display of results in a meaningful format (See TIME DOMAIN, FREQUENCY DOMAIN).
A measure of signal quality. Typically, the ratio of voltage or power of a desired signal to the undesired noise component measured in corresponding units.
The method whereby a physical process or device is identified in terms of the frequency characteristics of the signal it generates.
In data acquisition systems, the technique of using separate sample and hold amplifiers for each channel. This allows simultaneous sampling on all channels, thereby eliminating any skew due to use of a multiplexer (See SKEW).
See DEGREES OF FREEDOM.
Difference between sample times of sampled data in different channels of a data acquisition device. This results from multiplexing a single sample and hold amplifier among the channels (e.g., if 10 channels are scanned in 5 ms, there is a 0.5 ms skew between channels). Can also be due to head misalignment in a tape recorder.
The third moment of the probability density function of a random variable. It is a measure of the asymmetry of the function about its mean. A Gaussian distribution has zero skewness.
The general process of removing noise from data. Typically, it is performed by filtering a signal (provided that noise components are different in frequency than the desired signal).
See AVERAGE, STABLE.
A condition of a random process identified by the invariance of its statistical
moments with time; if only the first two moments (mean and mean square) do
not change, then the random process is weakly stationary; if all moments vary,
the process is nonstationary. The 
moment of a random process 
is defined as the expected value of .
See ERROR, STATISTICAL.
A random process where the current value of the process cannot be deterministically related to the past values.
The analysis of the loads and motions of the physical structure of a mechanical system. The analysis includes both dynamic and static analysis, although in the context of this document the dynamic analysis is emphasized.
See FINITE ELEMENT MODELING.
A trigger pulse which is used to synchronize two or more processes.
The process of modeling a dynamic system and experimentally determining values of parameters in the mathematical model which best describe the behavior of the system.