Friday, March 14, 2008


I taught a class several years ago that used various means of taking physiological measures. One of the measures taken was lung volume. We had two means of measuring lung volume.

The first was essentially an upside down bucket (it was actually a perfect cylinder) with the lip submerged in water. As you blew into the tube, it would fill the inside of the bucket with air and make the bucket rise in the water. It was well calibrated and there were some pens and a little motor attached to it. So the motor would turn some paper and the pens would mark on the paper as the bucket rose in the water. You ended up with a pattern on a piece of paper which you could use to calculate lung volume because the volume of the cylinder is known.

The second way of measuring lung volume was a little hand held device that you blew into. As you blew it would turn a fan which created an electrical current that was translated into lung volume. You could then read your lung volume on the handy digital readout.

When I asked the students which they thought was more accurate, almost all of them said that the electronic device was more accurate. Now I would certainly agree that the electronic device was more convenient, but the upside down bucket actually captured air and moved objects so that it was easily understood how much air had 'appeared' in the cylinder. Nobody could really explain how the electrical device worked, but they were sure it was more accurate because it gave a digital readout.

Just because a device is electronic and technologically advanced, does not make it better.

1 comment:

Heather said...

I just wanted to let you know that Earl got his bachelor's in Electrical Engineering, and he agrees with you.