Abstract: An improved bi-polar dual slope analog to digital converter having an automatic zero offset correction circuit using a high gain D.C. amplifier inserted between the output of the integrating amplifier and the input of the comparator amplifier, having both positive and negative reference potentials, and having a delay compensation circuit, for compensating delay produced by circuit elements in the signal path, coupled between the reference potentials and an input of the integrating amplifier.

Abstract: An improved thermocouple circuit condition detector for use in a measuring system requiring simultaneous analog trend recording and analog to digital conversion is disclosed. For analog to digital conversion the circuit testing period must be very short to fit in the time interval between conversions. For analog trend recording there should be no interruption of the analog circuit during the testing period and there should be no analog errors introduced by the testing circuit. All of these requirements are achieved by a novel pulse comparison circuit wherein a pulse by way of a direct path is applied as one input to a differential amplifier while that same pulse by way of the input terminal of the measuring amplifier which is connected to the ungrounded thermocouple lead, is applied to the other input of the differential amplifier. The detector alternately checks for open circuit and short circuit conditions.