Analog to digital converter

DETAILED DESCRIPTION An object of the present invention is to provide an improved analog to digital converter for converting an analog input signal into a digital count representative of the magnitude of the analog input signal.
In accomplishing this and other objects, there has been provided, in accordance with the present invention, an analog to digital converter comprising integrating means having an input and an output, means for applying an electrical signal to be converted to the input of the integrating means, switch means for selectively applying a positive and a negative reference signal opposing the input signal to the input of the integrating means, the integrating means being responsive to the application of the input signal and the second signal to produce an output signal at the output of the integrating means which ramps up and down between the positive and negative limits of the reference signal, level detection means responsive to two different levels of the integrator output signal to cause an output signal from the detection means to switch alternately between a first and a second state when the two levels are reached alternately by the output signal from the integrator means, flip-flop means responsive to a start edge of input signals applied thereto and having a signal input and a clock input, the signal input being connected to an output of the detector means, fixed frequency clock signal generating means arranged to supply clock signals to the clock input of the flip-flop means, AND gate means arranged to receive an output signal from the clock means and an output signal from one side of the flip-flop means, circuit means for connecting an output signal from the other side of said flip-flop means as an energizing signal to said switch means, and counter means arranged to count output signals from the AND gate means.