Abstract: An instrument for linearizing a non-linear analog output produced from a sensor such as a thermocouple to obtain a true measurement of the parameter or engineering units of interests. The full range of the non-linear analog output is divided into segments and within each segment the second slope or the rate of change of the first slope of the analog output is predetermined and stored. In carrying out measurements, the magnitude of the analog output sensed is converted to constant frequency pulses. When measurements are carried out, within a given segment the corresponding second slope data is employed to modify the frequency of the constant frequency pulses to obtain output pulses for accumulation. These output pulses have a frequency which at any given moment is representative of the first slope of the analog output and which changes at a rate representative of the rate of change of the first slope of the analog output.