At Interkama+: Battery-powered Magmeter Lasts for 15 Years

21 April 2009

When magnetic flowmeters were introduced back in the 1960s, their power consumption was something of an industry joke. They required so much electricity to operate the measuring coils, technicians referred to them as “water heaters.”

Times have changed, and design engineers have learned to work with more modest power budgets. It has come to this: at Interkama, Krohne unveiled what surely must be the world’s lowest power mag flowmeter: the Waterflux 3070. The consumption is so low, with two batteries and a sampling rate of 1/15 Hz it can run standalone for up to 15 years. This, says Krohne, is less electricity than a conventional electromagnetic flowmeter by a factor of 5,000 times.

It is designed to be used in remote locations, where no power is possible. It may be hard to think of a place like that in present day Europe, but there is a need for remote instruments communicating with GSM, especially in the water industry. Solar power systems set up as power supplies for remote measuring stations incur additional installation costs and are often vulnerable to vandalism and theft, say water industry spokesmen. Thus, the Waterflux may be equipped with an optional data logger and GSM module that transmits stored data once a day by an SMS message.

The secret to the instrument’s low power consumption is the unusually shaped measuring tube. On the outside it looks like an ordinary straight pipe, and is available in diameters up to 600mm. Inside, however, the tube has a smooth, conical shape that tapers down to a rectangular cross section (see photo below). The smaller cross section means the electrodes can be placed closer together and thus consume less power. The arrangement of the induction coils around the rectangular cross section produces a strong homogenous magnetic field, allowing measurement to be independent of flow profile. This also makes the extremely short inlet (three pipe diameters and outlet (one diameter) runs possible. The highly precise measurement (±0.2% of measured value ±1.5mm/s) makes it suitable for custody transfer.

The data logger can be programmed to only send measurement data or even to emit alarms in the event of specific operating states or flow values (right down to idling) which, for example, can be a sign of leaks or unexpected over-consumption. The module saves all flow data including peak values and low flows; the user thus obtains a precise flow value profile of the measuring station.

The data logger with GSM module for the Waterflux features its own battery which can deliver power for about 8 years. Up to four water meters can be connected at the same time.

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