A sensor circuit in a computer system measures a frequency of an oscillator circuit and uses the measured frequency to determine an operating condition of the computer system. The accuracy of the operating condition is limited by various sources of noise, including device noise, that introduce error into frequency measurements, limiting the accuracy to which the frequency of the oscillator signal may be measured. To improve the accuracy of the frequency measurement of the oscillator signal, the sensor circuit disables the oscillator between successive measurements, in order to reduce the correlation of error between the successive measurements. The sensor circuit combines the multiple measurement results to determine the frequency of the oscillator signal to a higher degree of accuracy, thereby improving the accuracy to which the operating condition is determined.