The flow rate measurement of the Portasonic® PRO is accurate to within 1%, under ideal conditions that is verified independently by an external ISO 17025 laboratory. Excepting the following caveats, the calculated pressure is always accurate to within ±5%. This accuracy holds for clean pipes, free of internal corrosion and residue build-up. It is also valid for temperatures between 10°C and 30°C. Temperatures outside of these bounds will, for the most part, still yield results of a similar accuracy, but these are as yet unverified. Finally, some graded liquids are listed under a general name, for example, crude oil. These take median values for the liquid properties, which will not necessarily be accurate for all grades.