How I use my sharpness tester to improve sharpening

[Bud]

KnifeGrinders you sound like a good person to ask this question. I just posted to another section of this forum with the guess that inconsistency in my grind angle (freehand on a Kally belt sander) is contributing to an inconsistency in edge tester readings along the length of a blade (as much as 40 - 50 points). I know it's not the edge tester or my technique because I've tested many different manufactured edges with almost perfect results. I realize that there could be other contributing factors (burr etc.) but do you feel that grind angle or pressure inconsistency alone could be a major problem? 

I don't mean to limit this question to KnifeGrinders. If someone else has an opinion to I'd be glad to learn what you think.