Water-Meter Calibration: Differences between the Traditional and the EHS Methods

The differences in calibration between the EHS and the traditional methods:

• with traditional “calibration”, the flow rates are measured just up to Qn (nominal flow rate which is e.g. 1,5 m3/h for ½” design), whereby with EHS, the water-meter parameters are measured within the entire possible range (Qmin, Transition flow-rate, Q max), thus incl. Qmax (maximum overload flow rate = 2x Qn which is e.g. 3 m3/h for ½” design)
• no pressure resistance measurement is done with traditional “calibration” while the pressure resistance measurement is done pursuant to EHS, even up to 1,6 multiple of the nominal pressure (in case of the BONEGA^® water-meters it is up to 1600 kPa); during this test and after having been pressurized, the water-meter (on a special stand) must not show any pressure drop over a period of one minute at least
• with the traditional calibration, the permitted measurement deviation can be +/- 2%, while pursuant to EHS (in case that all measured values are either plus or minus), the error tolerance can be only 50% of the permitted deviation, i.e. only up to 1%
• it is suitable to use the photometric measurement according to pulse number – the advantage consists in reading accuracy that can be – in contrary to the traditional one – in thousandths of liter

Selection of one calibration facility

Our exclusive and sole contractual calibration facility is Brněnské vodárny a kanalizace a.s., which has received the following accreditations:

• as the sole one in the Czech Republic – the accreditation pursuant to ČSN EN ISO/ IEC 17025 for water-meter calibration

• authorization for verification of the indicated meters, the verification seal has the license number K57

• It complies with the requirements as to ISO 9002

• It complies with the requirements as to EHS