The Apera Instruments ph400s provides reliable pH measurements with various intelligent functions and a durable structure. Equipped with apera’s 201t-s 3-in-1 pH electrode, the meter tests pH and temperature simultaneously in a quick and accurate manner. Also tests ORP (oxidation-reduction potential), ORP electrode is sold separately. Accuracy: ±0.01 pH/0.1 percent F.S; range: -2.00 to 19.99 pH. 0 to 100˚c auto or manual temperature compensation. Intelligent functions: quick & easy 1 to 5 points auto calibration with calibration guide and reminder. The SMART self-diagnosis helps you conduct proper calibrations and determine the condition of your probes. Glp data management (500 groups of data storage), USB data output and power supply with PC software support. Timing data logging and purified/ammonia-added purified water measuring modes available. The large white backlit LCD displays pH and temperature simultaneously along with icons of stable readings and finished calibrations. Reliable structure: IP57 waterproof and Dustproof, ideal for use in harsh environments. It comes with a complete Test Kit including a meter, a pH electrode, a USB cable, and 3 bottles of calibration solutions (pH 4.00, 7.00, 10.01) all in a rugged carrying case. Powered by AA batteries. The product is CE certified. Notes: this product will not give accurate or stable readings for distilled or deionized water's pH testing. This is because distilled and deionized water do not have enough ions present for the electrode to function properly. To measure distilled or deionized water’s pH, users need to use a specialized pH electrode. Do not store the probe in distilled water or deionized water because they will cause damage to the glass membrane of the pH probe. Only use distilled water for cleaning the pH probe. Parameter Models PH400S pH Measuring Range (-2.00 to 19.99) pH Resolution 0.1/0.01 pH Accuracy ±0.01 pH ±1 digit Temp. Compensation 0 to 100˚C (32 to 212˚F) Auto or Manual mV Measuring Range ±1999 mV Resolution 1 mV Accuracy ±0.1% F.S ±1 digit Temperature Measuring Range -10~110˚C (32 to 230˚F) Resolution 0.1˚C Accuracy ±0.5˚C±1 digit Others Data Storage 500 groups Storage Content Numbering, Date, Time, Measurements, Unit, Temperature Data Output USB -- PC-Link Software Power Supply AA Batteries*4 (1.5V*4) / USB IP Rating IP57 Waterproof and Dustproof Dimensions and Weight Meter: (7.8*3.4*1.25) inches / 12 oz. With carrying case: (19.5*14.5*4) inches/3.6 pounds