water meter

Water meters are instruments that indicate the volume of water has flowed through quantity. They are sometimes incorrectly referred to as a water meter. Most are water meters in commercial use, such as between utilities ( Stadtwerke ) and consumers, are used. In this case, the water meter must be calibrated ( calibration law ).

Water meters should be separated by a primary shut-off from the rest of the water mains so that the meter can be easily replaced.

History

During the industrialization at the beginning of the second half of the 19th century, the first private houses were their own water connections. Carl Wilhelm Siemens developed in 1851 in England a water meter, which indicated directly in contrast to previous designs, the amount of water consumed. In the lead an impeller was used, the speed of which is proportional to the flow. A gear transmission transferred the number of rounds on a counter. The device has been a huge success and was sold from 1858 also in Germany.

Types

Flügelradwasserzähler

For the measurement of small to medium amounts of water for nominal flow rates up to 15 m³ / h impeller flowmeters are used. Here still a distinction with regard to the measurement principles single beam and multibeam.

• In flat water meters is usually to single-jet: the flow of the impeller tangentially.
• When the domestic water meters is usually to multi-jet meters: the flow of the impeller is symmetrical from the outer surface of the measuring chamber. Thus, the amount of water acts uniformly on the impeller, thereby providing increased measurement stability and accuracy is ensured.

Volume counter

Flow meter is available with fixed or movable measuring chamber partitions, eg disc meters or rotary-piston meter.

Flow meter with turbines

As bulk water meters ( Woltmann meter ) used for nominal flow rates from 15 m³ / h.

Composite water meter

Compound water meters are a combination of bulk water meters as a main meter and a secondary meter for smaller flows. A Federumschaltventil automatically at high flow rates to the bulk water meters, so then both counters run parallel. At low flow rates, however, only the off timer is running. This design finds application where both small to medium flows, but occasionally large flows occur (industry, swimming pools, buildings with fire extinguishing systems ).

Display

This is indicated by the number and roles (for the low-order digits ) even by small hands with a decimal scale. After the procedure, the measured value shall be displayed in cubic meters ( black numerals ) that are fractions of a cubic meter are indicated by red numbers or pointers. Water meter can be equipped with contactors that emit eg see 1, 10 or 100 liters a pulse to an additional electronic counter for further processing. This technique is used for consumption data acquisition in building automation or for dosing additives. Some water meters have a digital counter with LCD and long-life battery. This technique, however, has not been enforced over the simple mechanical display.

Accuracy and load

The load (flow rate per hour) is divided and an upper region (Q2 = Qtrenn to Q4 = Qmax) in a lower range (Q1 = Q2 = Qmin to Qtrenn ). The nominal load Q3 = Qnom = half the value of Q4 = Qmax is indicated on the counter, such as Qn 2,5 m³ / h Normal domestic water meter (Qn = 2.5 m³ / h, class B ) have a minimum charge Qmin of 50 l / h, a cutoff Qtrenn of 200 l / h and a maximum load Qmax of 5000 l / h Since 2012 they are in accordance with rules of the DVGW ( German Association of Gas and Water Industry Association) as Qn 2.5 for 1 to 30 units, Qn 6 for 31-200 residential units and Qn 10 suitable for 200 to 600 units. In the lower region, the counter must be an error in the calibration is less than ± 5 % have, at the top of a maximum of ± 2%. In operation, the error can eg increase by erosion or deposition. The allowable error limit is twice the maximum permissible error.

Calibration, calibration validity period, in-service testing

The calibration year to recognize the so-called main temple ( seal ). On the one hand, the year is stamped, on the other hand, the identification number of the station or the Bureau of Standards. The verification period for cold water meters shall be six years, in Austria there are five years, due to the dimensional and Verification Act (§ 15 /5 ( a ) ), that is, a calibrated in 2010 meter shall to the end of 2016 ( Austria: end of 2015 ) remain in the network; for hot water meters it is five years. The water supply companies can (even several times ie if any) let out a sample test at a nationally recognized testing laboratory, the calibration validity period for a used in your area meter type (make, size) of a calibration year for three years longer.

If doubts about the measurement accuracy of a calibrated meter consist, you can make a request for in-service testing at a nationally recognized testing laboratory or the office of weights (after consultation with the water companies ). There, the counter is individually tested and issued with a test certificate. In practice, about 90 % of the tested meters are not objectionable.

Water meter and tenancy

If not all the apartments are equipped with a water meter in a house, the settlement after the living space can be. A landlord can use for utility billing and the data of a non approved water meter, if he can demonstrate that the information is correct.