I can't watch the full vid, I'm afraid it becomes obvious in the first 20-30 seconds that you don't have a clue what you are doing or what the tool is for.
Try building a wheel, If you have the 'feel' for it you will know what the spoke tensions are from the resistance at the spoke key. As an amateur who has built dozens of wheels I have never needed a spoke tensionometer to tell me the difference between one spoke to the next.
I'm not saying I haven't built duff wheels, just recently had to rebuild a wheel after spokes started to tear out of the rim, but this was a general over-tension situation rather than an imbalance.
The tensionometer is really for the microscopic wheel building analysis if you don't have a natural feel for mechanical things.