How to use GRIPX grip strength tester, grey

Engineered for home, sports, and clinical use, auto/manual shut off, 2* AAA batteries included.
Equipped with high precision strain gauge sensor, measuring capacity 198lbs / 90kgs with devision 0.2lbs / 0.1kgs.
A maximum grip value display and weak, normal or strong power levels can be saved and easily recalled for comparison.
The adjustable handle was suitable for users of different ages, a good fit for both big hands and small hands.
5 YEARS product warranty.