Apera Instruments AI209 PH20 Value Waterproof pH Pocket Tester, &plusmn;0.1 pH Accuracy, 0-14.0 pH Range, Complete Kit Easy auto. calibration with buffer recognition; auto. temp. compensation (ATC) ensures accuracy in various temperatures (32 to 122F) Backed by Apera quality pH sensor with low impedance, ensuring high response rate Comes in a rugged carrying case with pH 4&7 buffers and a lanyard Auto recognition of stable values improves consistency, so you don't have to guess when to manually hold measurement Up to 2000 hours' continuous operation, powered by AAA batteries