: he influence of measuring instruments on the recorded wave forms of explosion pressures has been investigated in a closed spherical vessel of 8 litres capacity.
    It is intended by this study to compare the explosion pressure waves recorded by some common measuring methods and to distinguish whether any difference exists between those recordings.
    One measuring system consists of a pressure transducer, amplifier and recorder, and experiments were carried out using two types of transducers (i.e., strain gauge transducers and piezo-electric transducer), three types of amplifiers and two types of recorders (i.e., electro-magnetic oscillographs and memoriscopes). Flammable gas used was that of hydrogen and air, and the concentrations of the mixture were about 30 and 50 volume % hydrogen in air.
    The results are shown in terms of the ratio of average pressure measured by one system to that by another system under various conditions. Comparisons are made about three magnitudes of explosion pressures; i.e., about 6, 8 and 10 kg/cm². Summarized results are tabulated by giving the degree of difference from one most common measuring system, which consists of strain gauge transducer, dynamic strain amplifier and electro-magnetic oscillograph, and this combination is nominated as a "standard system".
    From the results, it is shown that the differences are relatively small under practical experimental conditions and that the numerical differences in the magnitude of explosion pressures from the standard system are less than 3 % for 50 % gas mixture.
    For 30 % hydrogen-air mixture, the difference is more large with the system using a memoriscope for rather higher explosion pressures. This may be attributed to the following up characteristic of the memoriscope to faster explosion phenomena. Comparisons are also given for wave forms, and the frequency responsibilities of the instruments are discussed.