The device, which will be installed on your existing analog meter, is battery-powered and turns on for a fraction of a second a day, for a total of less than two minutes a year.
Please help explain to me the meaning of the bold phrase in the above sentence.
Many thanks!!!
It means that the device switches itself on (activates itself) for a fraction of a second every day (e.g. for a third of a second, a quarter of a second, or whatever). If you add together all those fractions of a second over 365 days of the year, the total is less than two minutes.