We had an inquiry today about whether or not our Marine Barograph app would read and record pressures accurate to a few tenths of a mb on a per second basis and plot then showing sub mb precision. The answer is yes it will, but the question caught my attention. I have known for a long time that pressure oscillates on a small scale at all times, but this never effects our weather work, which looks for solid trends of over a few tenths of a mb—in a sense for just this reason, namely we do not want small oscillations interfering with our reading, no matter where they come from.
When we look at a plot of the pressure on a fine scale we see these oscillations, but when you look at just one plot the tendency is to consider this electronic noise. You might think you are just looking at the limits of the sensor and its circuits. But that is actually not the case at all. These oscillations are real.
Below we see three old cell phones with our app loaded into them, converting them in a sense to about a $800 electronic barograph. Any iPhone model 6 or newer includes a pressure sensor—you may have one sitting around in a drawer.