Study on precise frequency measurement based on sound card

Making use of sound card of high cost performance to substitute data acquisition card, and combining with virtual instrument technique and beat method frequency measurement realizes high-precision frequency measurement. But the existence of the sampling rate deviation resulting from sound card crystal oscillator inaccuracy greatly reduces frequency measurement precision, so error mathematics model of frequency measurement is built to improve the measurement precision by use of the precise known sine wave signal and the result of measured frequency of sound card. It is made up of linear and sine wave. Linear parameter is gained by least-squares linear fitting algorithm, and sine wave model parameter is acquired by IEEE-STD-1057 algorithm. The experiment results show that the accuracy can reach 10^-5/s after the amendment model, which has reference value for precise frequency measurement.