Two weeks ago I described the general trends we saw when analysing the force-displacement data from breaking Pringles that had been left unsealed for a varying number of days. I stated that the feature that showed most correlation with the age and hence the crispness was the amount of force peaks after the major force drop. We have since produced a graph showing this trend. The graph is displayed below, we used the standard error derived from the three sets of measurements at each age for the error bars.
To be absolutely sure that we found a trend we decided to redo the measurements under different conditions.
In my last post I outlined our measuring equipment. We have since attached microphones to the equipment and have measured and recorded data for crisps. We started off looking at normal potato crisps, however, we soon realised that they were all different and it was impossible to get fair samples that only differed in age. We therefore, resorted to Pringles as they all have the same shape, texture and thickness.
We did measurements of singe Pringles to get a clear profile of the breaking but also did measurements with three Pringles stacked on top of each other to simulate a more realistic texture.
Our measuring instrument is a guillotine like device that we can use to break chips. For now we practiced with dry spaghetti as they are less messy and easily accessible. The two sensors we use are a load cell at the tooth of our guillotine to measure the force and a potentiometer to measure the displacement change as we move down. We filter the signal from the load cell using a self-made instrumentational amplifier and measure the voltages with an oscilloscope.
The photo of the oscilloscope output below shows a typical measurement outcome when breaking the spaghetti. The blue channel is proportional to the displacement while the yellow channel represents the force on the spaghetti.