One Data Acquisition System
As the phenomenon is very fast (a few milliseconds), HBK’s QuantumX MX840 8-channel amplifier with a maximum sample frequency of 19,200 Hz for all channels. Both the pressure transducers and the load cells were connected and recorded with the QuantumX controlled with catman software.
The ability to connect the six pressure transducers and the two load cells in the same data acquisition system and sample at a very high speed was crucial in order to compare the results obtained from both.
To verify the results, a comparison between the results of the pressure transducers and the load cells was made, integrating on the vertical section the pressure distribution determined with the P8AP.
The preliminary results showed a good agreement between the results of the pressure transducers and the load cells at low sample frequency. Increasing the sample frequency the agreement diminishes. Some sensors were positioned in a wet/dry zone in which the presence of a mixture of air and water during the impact, and the geometry of the P8AP, can lead to problems during measurement resulting from the compressibility of the air.
In order to solve the problem, the opening of the sensors was filled with glycerin and a vacuum was generated to avoid any vibration of the vacuum membrane and any loss of glycerin.
One of the next steps in the experimental campaign will be to improve the resolution in terms of pressure sensors through the acquisition of eight more sensors and another QuantumX MX840.