Overview
When choosing which instrument to use when
calibrating pressure, two of the more popular
choices are deadweight testers or digital pressure
gauges/calibrators with a pressure comparator.
Each has their advantages and disadvantages,
which are discussed in detail below.
Comparison
The deadweight tester has long been the standard
for pressure calibration. However, advancements
in technology have led to the development of digital
pressure standards worthy of consideration in
lieu of a deadweight tester. Understanding how to
contrast the two technologies is key to selecting
the appropriate solution.
Deadweight testers are systems that physically generate a known pressure. They may also be used as gauges to accurately measure system pressure. These devices
do not require a display, as the combination of the masses is used to determine the output pressure. They operate under the simple formula that pressure
is equal to force applied over a known area. The deadweight tester output is typically very accurate, even at its lower ranges. Industrial deadweights are available
with accuracies to ±0.015% of reading.
By contrast, digital pressure standards must be combined with a pressure source to generate a known pressure. Without the capability of producing pressure, the
digital standards are technically gauges. However, in the market, they may be called calibrators to distinguish them from the lower classes of digital indicators.
These digital devices are typically available in accuracies as a function of their full scale, such as ±0.050% of full scale (FS). However, advancements in technology
have led to some instruments specified as a function of the reading, similar to deadweight testers. Accuracies are available as low as ±0.025% of reading.
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