Check what the percentage refers to
Percent of reading and percent of full scale use different reference quantities and cannot be compared directly. Look for additional fixed terms, minimum-flow conditions and fluid restrictions. Accuracy, repeatability, resolution and system uncertainty also describe different things.
Why zero stability matters at low flow
Coriolis data sheets often express zero stability in mass-flow units. At low flow, this term can become a larger proportion of the measured flow. Some manufacturers specify a low-flow calculation, but it must not be transferred to another model without verification. Turndown alone does not establish error throughout the operating range.
Compare two operating points
For illustration only, a 0.5 kg/h error term represents 0.5% of 100 kg/h and 5% of 10 kg/h. This is a ratio calculation, not a meter performance claim, and it does not replace the manufacturer's complete error model. Differences between calibration and field conditions also require assessment.
- Request performance at minimum, normal and maximum flow.
- Distinguish meter performance, installation effects and reference-instrument uncertainty.
Ask for evidence that supports comparison
Request performance definitions, applicable flow ranges, zero stability, fluid and temperature/pressure conditions, and calibration or verification information. For batching or commercial measurement, review the complete measurement chain and totalisation requirements. A display reading zero once is not evidence that zero stability meets a specification.
