CXG-101 type magnetic tube adopts new controllable power supply and excitation control, the magnetic field strength of digital display, the magnetic field strength stepless linear adjustment, and the key components are greatly improved, which is more reasonable in structure, convenient operation, accurate measurement, reliable operation. In order to ensure the accuracy of the measurement, the magnetic field intensity of each magnetic tube is calibrated. Fully meet the requirements of experimental equipment for the test method of magnetite powder for coal preparation (GB/T18711-2002 seventh).