Abstract: In a dual slope analog to digital converter, the input amplifier has an input selectively connectable to an unknown analog source or a known opposite polarity analog source. The output of the amplifier is directly or indirectly connectable to its other input to change the gain of the output. A microprocessor controls the converter to sequentially connect the unknown analog source, instantaneously change the output connection to change gain where appropriate, and connect the known analog source.

Abstract: Determining the value of resistance directly, but inversely, based on conductance measurements, rather than directly, based on resistance measurements, is disclosed. A voltage drop of one polarity across a referenced resistance controls the charge rate of the capacitor of an integrator of a dual slope analog-to-digital converter for a known period of time. Thereafter the capacitor is discharged to a predetermined level (e.g., zero) for a measured period of time at a rate determined by a voltage drop of opposite polarity across an unknown resistance. The measured period of time is directly related to the conductance value of the unknown resistance and inversely related to the resistance value. The time measurement is stored in latches, which control a digital display.