Some things work for spme people, other things work for others. The wand method works the best as you can turn it slowly around to hit every part of the tank walls. However, as soon as you start usingvthe tank, the erroneous readings usually reappear. If you occasionally look down the tibe, you can see the levels for yourself. That is the only true method of keeping track of the levels. After you have camped for a while, you will know about how long you can go, te warning signs of getting full, etc so the black tank sensors are almost unnecessary.
Ben and Doreen
Home Away From Home - 2017 PT Crusader 315RST
TV - 2008 F250 Lariat 4X4 6.4 Diesel
42 nights camping in 2015
49 nights so far in 2016 (Still Not Enough!)