Atago Digital Waterproof pH Meter
Compact and portable, this affordable pH meter can accurately measure the pH values of a variety of liquids. It is easy to use, water resistant and perfect for many different applications including food and beverage production control as well as brewing and fermentation. Many sushi chefs use this pH meter to comply with food safety regulations concerning holding rice. Calibrates at two points (pH 4.0 and 7.0).
Dimensions: 1 5/8" x 2" x 6 1/4"
Weight: 3.17 oz
Measurement range: 0.0 to 14.0 pH
Resolution: 0.1 pH
Measurement accuracy: ± 0.1 pH (2.0 to 12.0 pH)
Operates on 4 x LR44 batteries
Click the below image to view Guidelines for Preparation of Sushi Products at Retail
It shows "Prepare acidification agent per recipe with target pH of 4.1 or less, but not to exceed 4.6". And sushi restaurants in NY state are required to have a pH meter for this purpose.