The ALD500AU/ALD500A/ALD500 are integrating dual slope analog processors, designed to operate on 5V power supplies for building precision analog-to-digital converters. The ALD500AU/ALD500A/ ALD500 feature specifications suitable for 18 bit/17 bit/16 bit resolution conversion, respectively. Together with three capacitors, one resistor, a precision voltage reference, and a digital controller, a precision Analog to Digital converter with auto zero can be implemented. The digital controller can be implemented by an external microcontroller, under either hardware (fixed logic) or software control. For ultra high resolution applications, up to 23 bit conversion can be implemented with an appropriate digital controller and software. The ALD500 series of analog processors accept differential inputs and the external digital controller first counts the number of pulses at a fixed clock rate that a capacitor requires to integrate against an unknown analog input voltage, then counts the number of pulses required to deintegrate the capacitor against a known reference voltage. This unknown analog voltage can then be converted by the microcontroller to a digital word, which is translated into a high resolution number, representing an accurate reading. This reading, when ratioed against the reference voltage, yields an accurate, absolute voltage measurement reading.