There is nothing pseudo scientific about using conductivity to measure moisture in soil. That's how the device works. Did you actually see it measure differently depending on the type of soil? What specifically was the difference? Obviously one has to calibrate these devices against some other observation. But in my mind measurements are always going to be better than common sense, unless of course you employ both.
If I were forced to choose, I would prefer careful observation to common sense any day of the week.
For the record, my plants are in the same kind of mix and I do not vary my water supply, so those are quite relevant assumptions. You can easily test the difference between two mixes or two sources of water using the device, to the extent they actually exist. That's the advantage of being able to rapidly test two things side by side using something that gives you a result in 2 seconds.
