Analog-digital converter utilizing multiple ramp integrating techniques

Analog-digital converter comprising an integrator (10) having an analog input signal (I.sub.1, U.sub.1) continuously applied to the input thereof and continuously integrating the signal;

• means applying an auxiliary signal (I.sub.2,I.sub.3,I.sub.c) to the integrator to cause the integrator to simultaneously integrate both the analog input signal and the auxiliary signal;
• a threshold switch (16) connected to the output of the integrator and changing state after the integrated output has reached a predetermined value;
• a pulse generator (17) providing output pulses;
• a first pulse counter (11), a bistable element (18), and a second pulse counter (12);
• the first and second pulse counters (11, 12) being connected in series and to the pulse generator to permanently count pulses of the pulse generator and the first pulse counter (11) being connected to set, at each overflow, the bistable element (18) into one of its stable states;
• and a logic network (23) connected to the threshold switch (16), the pulse generator (17), the second counter (12) and connected to and controlling the bistable element (18) to reset it to its other stable state by the output from the logic network (23), the logic network (23) providing an output when and only when the first pulse is produced by the pulse generator (17) after a change of state of the threshold switch (16) has occurred,
• the bistable element (18), when set upon overflow of the first counter (11), connecting said means applying the auxiliary signal to the integrator to provide an integrated representation of said auxiliary signal to the threshold switch (16) during the time interval said bistable element is in its set state;
• a third pulse counter (13,22,26) connected to said pulse generator and counting pulses from said pulse generator and having control connections with said logic network;
• and
• a pulse count recording means (20) connected to said third pulse counter (13,22,26) and incorporating calculating means for determining from the fluctuation of the least significant digit of said output value produced by said third counter (26) in a succession of said output values, a further decimal place for refinement of the digital value recorded;
• the logic network providing a further output controlling transfer of the count from said third pulse counter (13,22,26) to said pulse count recording means (20) and resetting said third pulse counter (13,22,26) during the time interval corresponding to two successive overflow pulses of the second counter (12) and during simultaneous integration of the analog input signal and said auxiliary signal.