Tough one. But if we assume you used the hannah and salifert correctly, I would follow them if I want to dose. Since they both correlate.Calibrated the Trident and it got accurate readings per the solution.
After the calibration:
Trident says 6.7 dKH
Hannah says 7.3
Salifert says 7.1
If I can’t trust the Trident to measure accurately, it’s a huge waste of a lot of $
Where do I go from here?
Dose Alk until Trident reads above 7?
Then, I know for sure it’s above 7 no matter what. And I can use Trident’s measurements to hold it steady.
Unless your trident prove to be accurate I would not take dosing decision based on its measurments.