The Primary Difference
A primary standard is desirable because its metrological qualities are such that it doesn't need to be calibrated or verified in order to be believed at its level of uncertainty claims. It can be expected to deliver accurate, reliable readings that satisfy the exacting needs of regulatory requirements, hold up under litigation proceedings and withstand the most taxing requirements of modern industrial process control.
The key to understanding gas flow measurement is in recognizing that there are seven primary units of measure, the SI base units (International System of Units). The SI base units have been quantified and refined worldwide and their precise values are unlikely to change. They include length, time, mass, electric current, thermodynamic temperature, amount of substance and luminous intensity.
Since there's no SI base unit for the direct measurement of gas flow, flow is best determined by measuring the time it takes to positively displace a known volume of gas. Volumetric piston provers, such as Bios products featuring Proven DryCal® Technology, are based on a century-old platform that's still considered by many – including national labs – to be the most desirable method of measuring gas flow, since the results are directly traceable to the SI base units.
Our patented technology is primary because it measures gas flow using the SI base units of length and time in order to derive flow: The interior diameter of our glass flow cell; the length of piston travel within this cell; and the time it takes the piston to travel this known distance. With Proven DryCal Technology products, customers receive accurate, directly traceable primary flow measurements that are fully supported by our leading laboratory accreditation. Pressure and temperature transducers in the flow stream allow conversion of the volumetric flow to standardized conditions. This differs from other gas flow meters and secondary systems that measure gas flow inferentially by measuring gas properties, such as energy transfer or heat transfer.
Bios believes in the Primary Difference, and we've proudly staked our reputation on it.
Find out why.