Gas flow calibration is evolving: While the Bell Prover remains a primary standard, Critical Venturi or Sonic Nozzle technology is increasingly dominating industrial applications. Offering continuous, pressure-independent calibration with minimal maintenance and an impressive turndown ratio of up to 4,000:1, Sonic Nozzles outperform traditional systems in flexibility and cost-efficiency. Despite the lack of primary standard status, critical nozzles achieve comparable measurement accuracy through precise calibration traceable to primary standards and high long-term stability.

For modern, cost-conscious calibration processes, Sonic Nozzles provide an efficient and future-proof alternative—unless regulations explicitly require a primary standard.