How accurate are the flow meters?

Precision varies from product to product and, for each flow meter, it is defined within the reference flow rate range. As a general rule, subject to verification on the product datasheet, we can summarize the accuracy of the flowmeters that we manufacture as follows:
Electronic flowmeters with oval gears +/- 0.5% (e.g. K200 – K900)
Electronic turbine flowmeters +/- 1% (e.g. Turbinox)
Mechanical flowmeters with oval gears +/- 1% (e.g. KM)
Mechanical nutating-disc flowmeters +/- 0.5% (e.g. K33, K44)