25
The DO probe has a built‑in temperature sensor.
The measured temperature is indicated on the display.
Allow the probe to reach thermal equilibrium before taking any measurements. This can take several
minutes. The greater the difference between the temperature at which the probe was stored and the
temperature of the sample, the longer the time will be.
Note: If “----” is displayed instead of the measured temperature, the DO probe is not properly
connected or the temperature is out of range. This also indicates the possibility of a broken
probe cable.
The following options are available for the Dissolved Oxygen calibration:
• One point automatic zero calibration at 0% saturation or 0 mg/L
• One point automatic slope calibration at 100% saturation or 8.26 mg/L
• Two points automatic calibration at 0% saturation (0 mg/L) and 100% saturation (8.26 mg/L)
• One point manual calibration using a standard value set by the user in % saturation or mg/L
When automatic calibrations are performed it is assumed that the standard value is the saturated DO
value at 25 °C, 0 g/L salinity and 760 mmHg.
When manual calibrations are performed it is assumed that the standard value is the DO value at the
current pressure, temperature and salinity.
Make sure the probe is ready for measurements (see probe connection and preparation on page 10),
i.e. the membrane is filled with electrolyte and the probe is connected to the meter.
For an accurate calibration, it is recommended to wait for at least 15 minutes to ensure precise
conditioning of the probe.
Remove the protective cap from the DO probe.
Make sure the salinity value has been set to the salinity of the standard (see SETUP for details).
INITIAL PREPARATION
TEMPERATURE MEASUREMENT
DO CALIBRATION PROCEDURE
One point automatic zero calibration
Submerge the probe into HI7040 zero oxygen solution and stir gently
for 2‑3 minutes.
Press CAL. The calibration menu will be displayed.
Press DO to select the DO calibration.
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