Calibrating a flow meter means first testing the meter for its unique deviation from reality, then altering the meter or program in some way to negate that unique offset. Each meter has its own flaws, quirks, and strengths well within the standards to adjust for in specific applications, and calibration tests are designed to identify these for adjustment later.
At first a two-by-two hypothesis matrix is used to determine if the meter reads a true positive, false alarm, covert failure, or true negative based on an assumption of how the meter will read. If it is assumed the meter is accurate and tests to read accurately the result is a true positive. A meter suspected to be inaccurate that reads inaccurately is a true negative. Other variations produce covert failures or false alarms. Balance between false alarms and covert failures is the key in flow meter calibration.
The perfect flow meter — zero calibrations, zero proving, no zeroing and zero worries with powerful diagnostics that can verify meter accuracy and give advance warning of changes — does not yet exist. Coriolis may arguably be the closest technology
because it is largely insensitive to fluid properties. It is predicted that within 10 years, on-board meter verification diagnostics will be a standard expectation in Coriolis technology.
Click here for the full article by Tom O’Banion.