Multislope converter and conversion technique

A method of converting a test signal into a digital indication of the test signal, said method comprising the steps of:

• (a) integrating the test signal for a run-up interval of known duration T;
• (b) integrating a discharging signal of regulable known magnitude and polarity to produce an integrator output signal varying in time linearly with the time integral of the test signal and linearly with the time integral of the discharging signal;
• (c) repetitively executing polarity tests of the output signal during the run-up interval and during a run-down interval subsequent to the run-up interval, said polarity tests defining a plurality of frames between successive polarity tests;
• (d) regulating the magnitude and polarity of the discharging signal in each frame during the run-up interval to have opposite polarity to that of the output signal at the most recent preceding polarity test;
• (e) regulating the magnitude and polarity of the discharging signal during the run-down interval to have opposite polarity to that of the output signal at the most recent preceding polarity test;
• (f) determining, from the known magnitude and polarity of the discharging signal as a function of time, the time integral of the discharging signal over the interval extending from the start of the run-up interval to the end of the run-down interval;
• and
• (g) producing the digital indication from the time integral of the discharging signal and the duration T of the run-up interval.

A method of converting a test signal into a digital indication of the test signal, said method comprising the steps of:

• (a) integrating the test signal for a run-up interval of duration T;
• (b) integrating a discharging signal of regulable known magnitude and polarity to produce a time integral of the discharging signal equal in magnitude to and of opposite polarity to the time integral of the discharging signal;
• (c) regulating the magnitude of the discharging signal to sequentially assume the values M.sub.k for k=1, . . . , N where N is an integer greater than two, where the k-th value is assumed for an integral multiple n.sub.k of a basic period of duration t.sub.d, and where the k-th value M.sub.k equals B.sup.N-k M.sub.N whereby successive values enable successively more sensitive base B places of digital conversion;
• (d) determining the time integral of the discharging signal;
• and
• (e) producing the digital indication using the time integral of the discharging signal and the duration T of the run-up interval.

A multislope analog to digital converter for producing a digital indication of an input test signal, said converter comprising:

• an integrator having an input and an output to produce at its output an integrator output signal varying linearly in time with the time integral of signals applied at its input;
• a first voltage source;
• a pair of resistors of substantially equal resistance R;
• a pair of switches connected in parallel to the first voltage source, each of which switchably connects the first voltage source to the integrator input through one of the resistors of resistance R;
• a plurality of resistors;
• a plurality of switches connecting said plurality of resistors from the first voltage source to the input of the integrator in a configuration which in response to control signals to the switches can produce a total configuration resistance from the first voltage source to the input of the integrator equal to B.sup.k R for k=0, . . . , n-1 for some integer base B and for some integer n>1;
• polarity means responsive to the integrator output signal for producing a polarity signal representing the polarity of the integrator output signal;
• a clock to provide a clock signal;
• a central processing unit coupled to the discharging means and responsive to the clock signal and to the polarity signal to periodically test the polarity signal and to supply control signals to the pair of switches and to the plurality of switches to produce a controllable discharging signal from the first voltage source to the input of the integrator;
• input switching means responsive to a signal from the central processing unit for applying the input test signal to the integrator for an interval of duration T;
• and
• calculating means coupled to the central processing unit for producing a digital value for the test signal from T and the magnitude and polarity of the discharging signal as a function of time.