Rozway pH Meter with backlight.  Range: 0-14.0 pH.  Resolution: 0.01.

You can use a pH meter to check the pH of your water, mash, [test Star San effectiveness] and finished beer.

Digital Pocket Size PH Meter/PH Tester/Water Quality Tester for Drinking Water, Hydroponics, Aquariums, Pools, Beer, Wine, Food, 0.01 PH Measurement – Extra PH Test Calibration Solution Pack