NAVI D-25 Instruction Manual page 72

● Calibrating with standard solution
D-52/53/54/55
2.9 Dissolved oxygen (DO) measurement (D-55)
Normally, air calibration is used to calibrate the meter
when measuring DO. When a higher level of measuring
precision is required, however, a two-point calibration
using standard solution can be employed.
Calibration order for zero standard solution and span
calibration solution is arbitrary. The meter automatically
determines the standard solution.
Preparing zero standard solution
Put 50 g sodium sulfate into 1000 ml of de-ionized water
and mix it until it dissolves completely.
Preparing span standard solution
Put de-ionized water into a container, and create an
oxygen-saturated state by bubbling the water with an air
pump.
Calibration procedure
1.
Press the CAL key with the initial screeen
displayed, to select the Calibration mode.
2.
Press the MODE key to display "SoL".
2 Taking Measurements
61