As part of my new release I wanted to verify that my reading were accurate. I used a Park TM-1 in the past, but the precision on the TM-1 is in units of 10 kgf or more, and the accuracy of one that is several years old and has been tossed around in a tool box is suspect. So I built a custom tension calibration rig. The idea is to measure the tension directly using a hanging scale, then use that to calibrate my app, and my TM-1 while I am at it.
Here is the picture so you can see what I am talking about.
First, with no tension on the spoke, the hanging scale is zeroed (tared). Then the spoke is tensioned to a set amount (115kgf in this case). The reading on the TM-1 should match, if not adjust the TM-1. In my case the TM-1 was off by about 10kfg. I adjusted and it matched the app much better than before.
After calibrating my TM-1, I tested the app performance and verify that the reading are accurate. \
Overall a useful tool for a shop or anyone who is building large quantities of wheels.