| 摘要 |
<p>PURPOSE:To detect an AC magnetic field within a short time, by calculating the standard deviation delta of the detection signal of a magnetic sensor and bringing the number N of times calculated from n=(sigma/Be)<2> corresponding to necessary magnetic field detection accuracy Be to the min. number of times and integrating the detection signal of the magnetic sensor. CONSTITUTION:An AC current is allowed to flow to an embedded pipe 1 from a predetermined AC power supply 4 through a transmitting part 2 to generate an AC magnetic field 5 around the pipe 1. The magnitude of said magnetic field 5 is detected by a magnetic sensor 6 and the detection signal is processed by a data processing part 7 to display the position of the pipe 1 on a display part 8. An integrating part 9 is provided between the sensor 6 and the processing part 7 and integrates the detection signal of the sensor 6 plural times in synchronous relation to the magnetic field on the basis of the synchronous signal 10 synchronous to the current sent from the transmitting part 2 to remove a noise magnetic field component. At first, the magnetic field 5 is detected plural times without integration to calculate the standard deviation delta of the detection signal of the sensor 6 and the integrating number (n) of times are calculated from said deviation and the necessary detection accuracy Be of the magnetic field 5 according to n=(delta/Be)<2> and made min. to integrate the detection signal of the sensor 6. By this method, the magnetic field 5 can be detected while at least the necessary detection accuracy is satisfied.</p> |
