Profile: Diamond Systems Instruments specializes in providing chemical test kits and pH meters. We also offer turbidity meters, titration systems, photometers, and dissolved oxygen bench meters. HI 4421 is a research grade dissolved oxygen bench meter with extensive capabilities in measuring DO as BOD (biological oxygen demand), OUR (oxygen uptake rate), SOUR (specific oxygen uptake rate), atmospheric pressure and temperature. DO measurements can be performed in ppm (mg/L) range and feature automatic or manual temperature & atmospheric pressure. Automatic and manual calibration of DO can be performed in one or two points using standard or user defined standards.