A Thousand and One Pressure Gauges
While visiting a friend in Seattle this past fall, I went camping in the beautiful Cascades of Washington. Because it was decided on a whim, we did not have the needed outdoor gear on hand, and so the trunk of our car carried with us a rather hodgepodge collection of equipment we managed to borrow from friends, including a beat up tent that was missing an unfortunate number of stakes. This, of course, was not realized until we were setting up in our little corner of the middle of nowhere at the black, cold hour of our late arrival. Liking to think of myself as a roll-with-the-punches sort of person, this discovery didn’t worry me, and I decided to use a few sturdy sticks to double for the missing stakes. What was quickly realized, though, was that compared to the appropriately designed stakes which slid into the cold, hard earth with ease, the wider, stumpy sticks did not budge. This is because the area of the sticks’ points was wider than that of the sophisticatedly svelte metal stakes. Thankfully, with a lot of grunting, we managed to shove the sticks deep enough into the ground and were eventually able to fashion our shabby, little tent into a respectable, if not entirely comfortable, sleeping quarters.
This seemingly insignificant hiccup is at the heart of what pressure means and what pressure measurements do. Pressure is, by definition, the force per unit of area applied against the surface of another object; to put it in mathematical terms, P=F/A. The sticks I attempted to use as stakes had wider surface areas at their points, therefore they did not effectively make the needed impression against the competing surface (the cold, hard ground of a mountain side). Adversely, the stakes pushed against and broke through the surface of the ground with ease; this is because the smaller surface area of their points concentrated the force of my pushing into a smaller area. The sticks had a greater surface area, thus less pressure; the surface of the stakes, though, was much smaller, ergo more pressure could be channeled and used appropriately.
This is pressure at its most basic and practical. Pressure is all around us, and pressure gauges are being applied for anything from the tires of my car, to the fuel being channeled in pipelines, to the atmospheric pressures of the earth. From air and water pressure gauges, high and low pressure gauges to digital and mechanical pressure gauges—these are all tools helping us stay safe in our homes, vehicles and workplaces.