The Apera Instruments pc400s provides quick and accurate pH and EC measurements with various intelligent functions and a durable structure. Equipped with apera’s high quality 3-in-1 pH electrode and BPA (brush-resistant Platinum black) conductivity sensor, the meter tests pH, EC, TDS, resistivity, and temperature 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, ±1 percent F.S; range: -2.00 to 19.99 pH, 0 to 200.0 MS/cm. Auto or manual temperature compensation.) intelligent functions: quick & easy 1 to 5 points auto calibration with SMART calibration guide and calibration reminder function available. The SMART self-diagnosis helps you determine the condition of your pH probe. Glp data management (1000 groups of data storage) with PC software support, USB data output and power supply. Timing measuring/data logging mode and purified & ammonia-added purified water measuring modes available. 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 conductivity electrode, a USB cable, and 6 bottles of calibration solutions all in a rugged carrying case. Powered by AA batteries. The product is CE certified. Notes: the instrument 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.