I use a cheap proform tester, and a calibration spring to make sure its right. Checked it against a Rimac tester as well, and it was within 4 lbs with a 400lb spring.

https://www.summitracing.com/parts/...R4rrZ5AIVgx6tBh1wiQhxEAQYAyABEgJcc_D_BwE

https://www.summitracing.com/parts/cca-5316/overview/