News

13 October 2005 , by Karin Björkin
« Tillbaka till nyhetsarkiv

A reliable robust system to remotely monitor water levels in dams and lakes. This was the order from power companies Fortum, Graninge and VB Kraft to Stockholm-based company BSAB.

The solution was a simple but sophisticated system that measures water levels and the status of dam gates at regular intervals and then sends these values using Mobitex to the power companies. 

”The system we developed consists of a pipe with a sensor that goes into the water and measures water pressure, which gives the current water level,” explains Stefan Sundlin, Product Manager and Systems Sales Manager at BSAB. “Other sensors ascertain the status of dam gates. There is also a data unit and a Mobitex modem that sends on the measured values.

The measurement system has a high level of reliability and is energy-efficient. It works for the most part anywhere, due to the robust Mobitex network. Power is provided by ten normal alkaline batteries, connected in series, which only need to be changed once a year.

“The batteries work in temperatures of as low as minus 40 degrees and would actually last at least five years, although the power companies change them once a year to be on the safe side,” explains Stefan.

Often in sleep mode

The secret behind the energy-efficient design is that, for most of the time, the system is in sleep mode.  A ”ten-year alarm” goes off on the machine once during every 24-hour period, which then receives instructions sent via Mobitex. These instructions can involve the machine ”waking up” from between one to four times over the following 24-hour period, collect measurement data and send them on before returning to sleep mode. Normally, only one measurement is needed every day but, when there is the possibility for floods in the autumn and spring, several values are required per day.

“Only small amounts of data are transferred so it goes very fast,” says Stefan. ”The transmissions only take a few seconds and then the machine returns to sleep mode which means that the batteries last a long time.”

Coverage in areas where nothing else works

The data unit, Mobitex modem and batteries are kept together in an inconspicuous metal container attached to a steel pipe. An antenna above this connects the Mobitex unit with the outside world. The system is completely self-sufficient and easy to install, even in locations that are not easy to reach.

“Laying electricity cables would be too expensive and the solar power panels that were used previously were often stolen, “explains Stefan. “So this design is perfect for the power companies.”

The power companies’ dams and regulated lakes are often located off the beaten track, something which puts the wireless communication system to the test.

“The Mobitex network offers coverage in areas where nothing else works and the wavelength used can also penetrate forest areas. The Mobitex unit is also constructed using modern electronic components that are very durable.”

Just keeps on going

BSAB also supply the software used to manage and process the reported values. Several potential customers have shown an interest in the technology and, so far, experiences have been very positive.

“The power companies have been using the system for many years now and it has worked without any problems,“ says Stefan. “It just keeps on going.”

(Article taken from Multicom Magazine nr 3/2005)