As automated processes revolutionize the world of metrology, there's a growing debate that manual deadweight testers are troublesome and in need of updates. Heavy external mass loading, separate environmental calculations, and slower calibration time may justify these concerns. If pressure controllers can accurately measure pressure in seconds, why would we still want to use deadweight testers? In this blog, we'll explore deadweight testers' role and impact on metrology.

What are deadweight testers?

Deadweight testers calibrate pressure-measuring instruments by applying calibrated masses over a piston area. The medium under the piston is increased in pressure to ‘float’ the piston. The goal is to establish an equilibrium between the known reference pressure and the DUT (Device Under Test).  Due to their SI unit-based measuring principle and lack of electrical components, deadweight testers are regarded as one of the most precise and traceable pressure-measuring instruments available. They are most beneficial to industries requiring higher accuracies and traceability. For instance, deadweight testers with portable and durable designs would be perfect for quality assurance processes such as power plants and maintenance facilities.

What are primary standards?

The International Vocabulary of Metrology defines primary standards as measurement standards that establish their quantity value and measurement uncertainty using a primary measurement procedure. In other words, a primary instrument is used as a standard reference to calibrate DUTs. Deadweight testers are the first to come to mind when referring to primary pressure standards. However, it's important to remember that some industries define primary pressure standards differently.

Advantages

There are many advantages to using a deadweight tester for calibration. They use mass and a stable piston and cylinder system to create pressure, providing consistent and traceable results. Various options are also available to accommodate different DUTs, environments, and pressure ranges. One can choose pneumatic or hydraulic deadweight testers, as well as digital or manual ones. The deadweight tester calibration covers low, mid, and high-pressure levels.

Disadvantages

Of course, some drawbacks must be addressed. Deadweight testers can not compete with fast pressure controllers, such as the CPC3050. While the precision is unmatched, they're not ideal for industries prioritizing speed over higher accuracies. Factors such as gravity, the piston's temperature, and barometric pressure can also affect the pressure calculations. These environmental conditions need to be factored into the equation. Finally, more labor is involved than automated processes, such as spinning the masses and waiting for stabilization, all for only one reading.

But how do they compare to automated calibration instruments like pressure controllers?