The HI98100 Checker Plus is the most popular pH meter in the world with over 1 million meters used since its intro in 1991. From entry-level growers to professional horticulturalists, it has been helping people with their pH measurement as a meter that is simple to use. It has been designed with many advanced features while maintaining the look and feel of the original Checker. It now offers automatic calibration to one or two points, automatic buffer recognition, calibrated buffer tags, stability indicator, low battery indicator, and selectable automatic shut off. One button operation -One button for set up and calibration Economical -It is a full-featured pH tester at a price that anyone that needs to measure pH can afford. Large LCD -Enhanced LCD that displays reading, stability indicator, low battery indicator and calibration tags. Replaceable pH Electrode -The HI1271 supplied gel filled pH electrode is 103 mm long and tapers to an 8 mm diameter at the sensing end. This narrow electrode easily fits into test tubes, vials, and other containers with small opening. Automatic Calibration -It is calibrated automatically to one or two points. The calibration buffers are automatically recognized and after calibration the buffer values used are shown on the display as a tag. Stability Indicator -An hourglass indicator is displayed on the LCD until a stable reading is obtained. Once a reading stabilized the indicator disappears and a reading can be recorded. Automatic Shut-Off -The meter can be set to automatically turn off after 8 minutes or 60 minutes to conserve battery life in the event that the meter is left on. The auto off feature can be disabled. Long Battery Life -It has an exceptional long battery life of approximately 1000 hours. When the battery power is running low a low battery indicator is displayed. Plastic Carrying Case -It is supplied complete with meter, probe, calibration solutions and cleaning solutions packaged in a durable plastic carrying case.