Test & measurement
MEASUREMENT FIDELITY THE CORNERSTONE OF PRECISION IN INDUSTRIAL PERFORMANCE
M
easurement fidelity is the cornerstone of accurate data collection, essential for industries ranging from aerospace to automotive engineering.
Fidelity of a system is defined as the ability of the system to reproduce the output in the same form as the input. It is the degree to which a measurement system indicates changes in the measured quantity without any dynamic error.
It is about how well a device can present the real- world phenomenon it is measuring.
Pressure scanners are available that use a native differential pressure sensor which senses a live reference and surface pressure measurement simulta- neously and its output is a direct, uncalculated function of both of these influences. Similarly, a pair of abso- lute-mode sensors can be used where one is reacting to changes only in the local barometric pressure while the other reacts to changes in the surface pressure, an arithmetic sum is then applied between these sensors to create the differential measurement.
In the native differential sensor, the accuracy of the measurement is generally around the 0.06 per cent level, so on a 100mbar range a measurement accuracy of
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0.06mbar can be safely attributed. If a pair of absolute mode sensors is used, typically, these will have a meas- urement range of 1200mbar with an accuracy of around 0.1 per cent. This means that each sensor typically yields a measurement performance of around 1.2mbar, and when two sensors are used to produce a combined measurement, this can reach 2.4mbar in this case. When comparing the technologies, it can be seen that for the same effective range, the native differential measurement can be up to almost 50 times more accurate than the absolute derived measurement. This is before we take under consideration the resolution of the same measurement, which is also at a higher level in the differential device, and before we get even further up the measurement chain to components like A/D converters which vary between 16 and 24-bit in the current market, which can impact overall measure- ment fidelity in the instruments.
Add in temperature compensation, engineering data conversion and, in some cases IEEE1588 PTP level data synchronisation, and overall measurement performance can be significantly impacted. All of this and some meas- urement systems can exceed 1,500 channels, that is a lot of data to collect, read and output, accurately.
ALL PRESSURE SCANNERS ARE NOT THE SAME!
Enter EvoScann and Scanivalve pressure scanners, available from Evolution Measurement, exemplars of precision in measurement technology. Providing true differential measurement in the majority of scan- ners, these systems stand out for their commitment to achieving unparalleled measurement fidelity. The integration of high-speed, high-resolution ADCs further enhances measurement fidelity. These converters boast remarkable sampling rates and resolution, allowing for the capture of intricate signal details with exceptional precision. As a result, EvoScann and Scanivalve pressure scanners can distinguish minute variations in pressure (down to as low as 0.00008Pa change), providing insights with remarkable granularity.
This level of detail is invaluable in applications where even slight deviations can have significant implications, such as in aerodynamics testing or combustion analysis.
Evolution Measurement
www.evolutionmeasurement.com January 2025 Instrumentation Monthly
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