The Extech SDL150 records data on an SD card in Excel format. It has a dual backlit display of oxygen concentration and temperature. It measures dissolved oxygen from 0 mg/L to 20.0 mg/L and 0% to 100.0% oxygen, plus temperature from 0°C to 50°C (32 to 122°F). Includes automatic temperature compensation from 0°C to 50°C via temperature probe sensor built into polarographic type oxygen probe. Offset adjustment used for zero function to make relative measurements. The SDL150 stores 99 readings manually and 20M readings via a 2G SD card. User programmable sampling rate. It has a built-in PC interface, min/max and data hold functions, and an auto power off. Complete with 6 x AA batteries, SD card, probe, two spare replacement membranes, electrolyte, and hard carrying case.