The first one I bought (Proform 0-300# or something comparable?) was a piece of junk. I also have a claibration spring and it was nowhere near accurate. IIRC, it started off OK, then started getting more "off" after using it only a few times.

The second one I bought was a 0-600# from a board member (vendor) whose name I cannot recall at the moment, unfortunately. That one has worked fine. Maybe he'll see this thread and pipe in.