Design of a precise current source with adjustable frequency for AC-FSM

AC-FSM is a new technology of external monitoring the internal corrosion for oil and gas pipelines. The current source stability of the FSM equipment is one of the important factors affecting the monitoring accuracy. According to the equipment requirements, a precision current source with adjustable frequency is designed. With C8051MCU as the control core, DAC conversion and differential amplifier are used to control the frequency and the current amount. The experiment shows that the output of excitation power supply has good consistency, the changing range was less than 0.3 %. When the temperature changes, under the condition of low frequency 5Hz, the change of current is less than 0.5 %, under the condition of high frequency 102Hz, the change of current is less than 0.4 %, which avoids the influence of temperature drift. This equipment is suitable for the long period operation of oil and gas pipelines in the field.