The HI 98121 pH/ORP Tester is a waterproof combination pocket pH, Oxidation Reduction Potential (ORP) tester with a replaceable electrode and a non-clogging, replenishable fiber junction.The meter features a large LCD screen for readability, an ergonomically designed waterproof casing, and automatic temperature compensation to eliminate the need for additional calculations. It has a replaceable electrode and renewable reference junction, which helps prolong the life of the tester.The HI 98121 tester functions in temperatures of -5.0 to 60.0 degrees C/23.0 to 140.0 degrees F (+ or - 0.1 degrees C / 0.1 degrees F), and has a range of -2.00 to 16.00 pH (+ or - 0.05) with a resolution of 0.01 pH. The meter can be calibrated at one or two points for pH with auto-buffer recognition, and against five memorized buffer values. For ORP (Oxidation Reduction Potential) readings, the tester has a range of + or - 1000mV (+ or - 2) with a resolution of 1mV and automatic factory set calibration. Dimensions are 163 x 40 x 26 mm (6.4 x 1.6 x 1.0"), with weight 100 g (3.5 oz.).pH testers measure the acidity or alkalinity of a substance and are commonly used by researchers, manufacturers, and hobbyists.Hanna Instruments manufactures a wide variety of analytical instrumentation, including pH meters, multi-parameter meters, electrodes, chemical reagents, and buffer solutions. Founded in 1978, Hanna is headquartered in Woonsocket, RI, with subsidiaries in 32 countries. Hanna Instruments holds many firsts in the field of analytical instrumentation, including a pH electrode with a built-in temperature sensor, an electronic pocket-sized pH tester, and a replaceable electrode pH pocket tester. To ensure the quality of its products, Hanna is a vertically integrated manufacturer and does not subcontract any part of its manufacturing.What’s in the Box?Protective capCalibration screwdriverFour 1.5V batteriesInstructions