An analog-to-digitial converter of the dual slope type wherein simultaneous integration of two input signals is achieved to provide a digital output substantially immune to disturbances affecting both signals. First and second dual slope converter circuits are employed, each receiving a respective analog signal. During conversion of the first signal, integration of the second signal is accomplished such that a digital output signal is provided representing the integrated instantaneous ratio of the two input signals and which is substantially free of disturbances affectng both of signals which may be introduced during a conversion cycle.