Woltmann counter

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Woltmann counter

Woltmann meter are water meter for nominal flow rates (Q n) of 15 m³ / h to 1,500 m³ / h, which operate on the principle Woltmann. This is the principle of measuring currents using hydrometric blades, described by the German hydraulic engineer Reinhard Woltman in 1790. Typical pipe diameters range from nominal sizes DN 50 to DN 500.


The flow through the wing, made of helically twisted blades, is parallel to its axis. The pipe cross-section is carried out in the Woltmann meter without any significant constriction. This results in very little pressure loss. Since the impeller is driven by the dynamic action of the water (kinetic energy = speed energy), we also speak of speed counters here. The rotary movement can be transmitted to the overhead counter via a worm gear or the so-called “dry” counter is driven by the turbine wheel running in the water via a magnetic coupling.


  • WP: turbine meter with parallel pipe axis (small pressure loss)
  • WS: Turbine meter with vertical pipe axis (greater pressure loss, but less sensitive to influences from preceding pipe bends)
  • Models with approval for cold or hot water


The following information is used for the design and type identification:

  • Qmax: Largest flow rate, only permitted for a short time, i. H. about 15 minutes a day.
  • Qn: nominal flow rate = 1/3 - 1/2 of Qmax. This value also serves to identify the counter.
  • Qmin: smallest flow from which the meter must comply with the error limits.
  • Qt: Transitional flow rate (also called separation limit), transition point from the smaller to the larger permissible display error.
  • h WZ: pressure loss in the water meter.
  • MAP (maximum admissible working pressure) Pressure level of the water meter, max. permissible operating pressure in bar
  • PN (16) flange size related to the nominal diameter (DN)


The display is usually made by means of number rollers and (for the lower-order digits) also by small pointers with a decimal scale. According to the regulation, the measured value must be displayed in cubic meters (black digits), the fractions of a cubic meter are displayed by red digits or pointers.

Encoder device

The Woltmann meters can also be provided with encoder devices such as:

  • electromechanical contactors, which give an electrical pulse after certain quantities flow through and thus z. B. on or off the water supply via a valve or an electr. Remote counter or an electr. Operate the quantity recorder or the pulse printer.
  • electronic pulse generators with downstream transducer for flow measurement or registration. The count then also becomes a flow measurement.
  • Combinations of both, e.g. B. an electromechanical remote transmission of the meter reading through built-up contactor and remote measurement and registration of the flow by means of an infrared transmitter.


Large water meter Qn 600 m³ / h

Typical applications can be found in the pipe network of water suppliers, with large customers and in industry.

See also


Individual evidence

  1. Dictionary ( Memento from February 3, 2015 in the Internet Archive )