The Professional Dissolved Oxygen Meter HD3030 is a top range meter for field use. Each meter comes with a 3 meter probe for submerged testing under water in streams, ponds or water tanks. Users can preset salinity compensation and atmospheric compensation to allow direct reading without any conversion tables. It can store up to 99 memory with date and time records. To allow night visibility, there is a backlit display handy. The HD3030 is suitable for aquaculture or industrial users. Advanced Features: Dual DO and temperature display One touch calibration in air Able to set salinity and atmospheric pressure compensation Save up to 99 data in memory with real time clock Make online data logging on PC with optional RS232 kit Able to show maximum and minimum reading over saved data Backlite for night display