Abstract: An analog-to-digital converter which is supervised by a microprocessor and includes means for digitally compensating for initial gain and offset errors and gain and offset drift errors due to temperature variations. An analog input voltage is applied to a first analog-to-digital converter, the output of which is both stored in the microprocessor and applied to a linear digital-to-analog converter. The output of the linear converter is summed with the original analog input voltage and the difference applied to the conversion apparatus as an unknown input signal. This process is continued to achieve a desired resolution. The output of a differential temperature sensor is similarly processed to determine the proper amount of compensation for gain and offset drift. The microprocessor provides both control and computation capabilities.

Abstract: A digital to analog conversion system includes a memory for storing a plurality of correction codes corresponding to corrections required to compensate for inaccuracy in output currents of a main digital to analog converter (DAC) contained in the digital to analog conversion system. A plurality of the logic inputs applied to the inputs of the main DAC are also applied to the address inputs of the memory. A trim DAC having its inputs coupled to the data outputs of the memory converts the correction code stored in the addressed location of the memory into a correction current which is utilized externally of the main DAC to modify the net amount of output current available from the main DAC to compensate for inaccuracy of the unmodified output current. An output signal from a temperature sensor is connected to a digital number which is also applied to a plurality of the address inputs.

Abstract: A system for automatically calibrating a main digital to analog converter (DAC) includes first and second adjustment DAC's, an offset DAC, a difference amplifier, an analog to digital converter (ADC), a microprocessor, and an analog switch. To calibrate the offset of the main DAC, the microprocessor causes "zeros" to be applied to the digital inputs of the main DAC and the offset DAC. The output of the offset DAC is coupled to an input of the difference amplifier. The microprocessor causes a ground voltage to be applied to the second input of the difference amplifier via the analog switch. The output of the difference amplifier is inputted to the ADC, which produces a first word. The first word is stored by the microprocessor. The analog switch is activated to apply the analog output voltage of the main DAC to the second input of the difference amplifier. The ADC produces a second word which is compared to the first word.