A system for measuring low levels of electrical energy

Claim 1

A sensing apparatus comprising a condition responsive source means adapted to generate a low energy electrical output signal proportional to a sensed variable condition, an energy storage means coupled to said condition responsive means and adapted to accumulate energy received therefrom, output circuit means coupled to said energy storage means, electrical switch means connected between said source means and said energy storage means, switch control means operatively coupled to said switch means and adapted to automatically and repetitively produce alternating energy storing periods of uniform duration wherein energy at relatively low power levels provided by said condition responsive means is accumulated by said energy storage means and energy discharge periods of substantially shorter duration than said energy storing periods, said energy accumulated by said energy storage means being substantially instantaneously discharged into said output circuit means during said discharge periods at power levels substantially greater than said relatively low power levels, measuring means coupled to said output circuit means and adapted to receive and measure during said energy discharge periods the energy received from said energy storage means, condition control means for controlling the variable condition sensed by said condition responsive source means, said condition control means being operatively coupled to said measuring means and responsive to the level of energy received thereby from said energy storage means.