You guys know I am a digital kind of guy who likes things with readouts, etc. so I have given this issue a lot of thought. I read the extensive and sometimes contentious thread on another forum discussing a magazine article by Mark Duginske (nationally recognized woodworker and author of an outstanding bandsaw book). Duginkse eventually weighed -in. He teamed up with a professional engineer to do testing of after-market bandsaw tension gauges. They determined most, if not all, were not accurate, reliable, nor repeatable, certainly not enough to justify their cost. Even DIY gauges using calipers, strain gauges, etc. were not reliable. If I remember they tested the Carter (mechanical), Lenox, and Iturra gauges. Their bottom line- the bandsaw manufacturers' marks are as good as anything. I tend to agree, but asked about the Carter electronic load-cell based digital systems ($150/$200) where the load cell is placed under the foot of the tensioning rod. I didn't get a satisfactory answer.
But, after thinking more about it, I had an epiphany. What is bandsaw tension, how is it determined and why is it needed? My take is it is not needed for anything but gross initial setting and short-term repeatability then it is up to the woodworker to tweak it. Think about it- where does a manufacturer's recommended tension setting, if there is one, come from? Trial and error through testing by a bunch of woodworkers testing that blade on bandsaws. They are combining an objective tension readout of some sort with a purely subjective determination of where a blade works best. There is no other way to do it!
So, if the only way to determine the best (tension) setting is by human trial and error, the results can vary. On top of that, any setting may change depending on blade age, temper and sharpness, as well as the thickness and hardness of the material being cut. I firmly believe there is no magic bullet. My recommendation is to experiment and learn your bandsaw. Learn what works and doesn't work for a particular blade. Once you find the tension where a particular blade cuts well make a mark on the saw. For a new blade you can't go wrong starting out with the manufacturers' marks. If your saw doesn't have marks try the vibration method.
Like anyone, I would love to be able install a blade and dial in a precise tension published for the blade, have the blade will work perfectly, and make me a better woodworker. Ain't gonna happen.