The initiator under test is activated by a pre-set pulse current from the launcher. After initiation, the pressure profile generated by the initiator into a defined closed volume is scanned. Pressure measurement is provided by piezoelectric pressure sensor with charge preamplifier from Kistler.
System is based on PC measuring technology. Firing current and pressure waveforms are measured with two 14-bit AD-14 measurement cards having sampling rate of up to 250 kSa/s and pre-trigger.
The measurement flows in series. At the beginning of the series, the operator selects the type of measurement. Each type of measurement corresponds to the setting of other parameters: test temperature, magnitude and length of current pulse, etc. The program allows to define new types of measurements and to change the parameters of existing ones.
Self-test follows. After each launch, the window with the most important values is evaluated and displayed. A number of important points (eg. maximum pressure, time to reach a certain pressure, etc.) are subtracted from the measured courses. The operator is also informed about climatic conditions in the firing range (temperature, humidity). By pressing the softkey he can see the table, which contains calculated values from the tests performed so far. From the graphs it is possible to read individual values using the cursors …
The figure shows a snapshot of the evaluation window with typical current and pressure waveforms. The bottom graph also contains a tolerance field (shown by a dashed line) that defines the limit values for the pressure curve – according to these values the program determines whether the product complies or not.
After measuring the whole series, the measured values are archived. Test results are documented in a log file and archived on an optical disc. Even at this stage, the program offers a number of options – evaluation of just measured or archived data, measurement protocol of the whole series or individual pieces, etc. Typical protocol is shown in the figure.
The program also supports activities such as pressure sensor calibration, current firing impulse control or tolerance field setting. The program emphasizes the flexibility of changing various parameters, as measurement conditions and evaluation criteria change frequently.
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