The science of measurement is called metrology, and it is primarily concerned with the establishment of measurement units, the realization of measurement standards and the transfer of these standards to industry by means of calibration.
Dynamic vs. Static Measurement
Most linear measurement is static. It is performed on something that is stable and unchanging, at least over a short period of time. Dynamic measurement, by comparison, is the continuous monitoring of a changing quantity. However, the most imporant distinguishing feature of this type of measurement is the speed of response of the measurement system compared to the speed at which the measured signal is changing.
A measurement is considered to be dynamic when the value of the physical quantity being measured varies over time, and where this variation may have a significant effect on the measurement result. Lower accuracy and a higher degree of uncertainty than with static measurement are associated with dynamic measurement. Sensitivity may vary with amplitude & frequency.
This type of measurement is common in many applications, including thermometers, vehicular acceleration, and the calibration of high speed electronic devices, to name but a few. It is carried out by shock sensors and accelerometers that have been specifically created to provide diagnostic information and accurate measurements across a broad range of industries.
Dynamic Error
A dynamic measurement system is ideally designed so that its output signal is proportional to the input signal. However, this can often only be achieved for output signals with a low-frequency spectrum. For input signals with large bandwidth, the output signal of the measurement system is, in most cases, no longer proportional to its input signal.
A dynamic error occurs when the output signal of the measurement system is taken as a time-dependent estimate of the value of the measurement (acceleration, force, pressure, angular acceleration and torque). To compensate for this, a digital filter needs to be used to process the output of the measuring system.
When designing a compensation filter, the dynamic behavior of the measurement system needs to be characterized. In other words, the measurement system has to be identified. The determination of measurement uncertainty plays a key role in metrology.
Watson Industries manufactures a range of accelerometers for accurate dynamic measurements. Go to website for more information.
