Abstract: When measuring the axial output of an explosive element with bottom case by a manganin sensor, a protective medium should be added to the front of the sensor. PMMA and Mylar films are selected to protect the sensor when measuring a No.1 electric detonator. By analyzing the measured waveform hydrodynamically, the following conclusion was obtained: the use of 1 mm PMMA compared better than a 0.05～0.10 mm Mylar film when measuring explosive elements with fragments.