Abstract: On the basis of Hall effect measurement of magnetic field in excitation

solenoid，the experimentalcontent of magnetic field measurement was expanded in this article by placing an iron tube

coaxially in solenoid. Ex-perimental result showed that the intact iron tube in excitation solenoid hac almost

zero internal magnetic field. However，if the iron tube had material defects，an obvious magnetic

leakage signal could be measured at the corre- sponding axis position. This extended experiment

not only strengthens the experimental training of magnetic field measurement，but also enriches the basic experimental techniques of magnetic shielding and defect magnetic flux leakage detection.

Key words: magnetic flux leakage detection, magnetic induction, iron tube