Design of High Power and Ultra-Low Frequency Signal Source

The cased hole resistivity logging technique requires high power, ultra-low frequency signal sources. Based on the characteristics of the signal, the direct digital synthesis technique was applied to produce the sine logging exciting signal, series devices of low power and low voltage were also used to produce the signals of high power and high voltage, and power tracing technique was used to lower the dissipation of power devices, and to improve the circuit working efficiency. The results show that the output frequency of signal source is 0.01~15 Hz, frequency resolution 0.004 Hz, frequency stability ± 2.5 × 10^-5 per half hour, output voltage scale ± 300 V, output current ¿ 6 A, output power 900 W. And the signal source parameters meet the logging experiment demands of 3,000 m cable.