Different devices can disagree
Hydraulic, digital and spring-based devices may not read identically. If you change dynamometers, treat the new reading as a new baseline instead of assuming the difference is a strength change.
Handle position matters
Grip width changes leverage. Record the handle setting that feels strongest and use the same setting for future tests.
Repeatability beats features
For personal tracking, a plain tester that gives stable repeat readings is more useful than a complicated device with inconsistent measurements.
Need a tester?
Use one device consistently.