I have noticed a distinct difference between my Trident and my Hanna checkers. Sit back, I got some data for ya.
3-6 Set up Trident
3-9 dKh Hanna = 9.5 Trident = 10.9 delta 1.4
CA Hanna = 473 Trident = 540 delta 70
3-10 dKh Hanna = 9.4 Trident = 11.1 delta 1.7
CA Hanna = 543 Trident = 538 delta -5
3-17 dKh Hanna = 9.8 Trident = 11.2 delta 1.4
Retest for belief dKh Hanna = 9.5 Trident = 11.2 delta 1.7
CA Hanna = 473 Trident = 455 delta -21
Retest for belief CA Hanna = 538 Trident = 455 delta -83
3-31 dKh Hanna = 8.1 Trident = 8.2 delta 0.1
CA Hanna = 491 Trident = 431 delta -60
4-1 Replace Trident due to waste line not being connected
New Trident measures closer to Hanna
4-11 dKh Hanna = 9.4 Trident = 9.7 delta 0.3
CA Hanna = 392 (did not write down Trident but noted closer delta)
4-28 dKh Hanna = 8.9 Trident = 8.97 delta 0.07
CA Hanna = 404 Trident = 571 delta 167
In short, the first Trident seemed to be off in dKh from my Hanna while the next unit tracks dKh very well, but trends high on CA by about 70-100 ppm. The trends are pretty good and so I trust both about as far as I can throw them. The Hanna being a little more because it's closer to a baseball than the Trident.
Ask me if you want to see my data book