Hach-Lange SI794 D User Manual - Manual (Page 65)

Calibration
It is always recommended to calibrate in air.
Compared to water, air is a calibration medium which is easy to
handle, stable, and thus safe. In the most cases, however, the
sensor must be dismounted for a calibration in air.
When dealing with biotechnological processes which require
sterile conditions, the sensor cannot be removed for calibration.
Here, calibration must be performed with aeration directly in the
process medium (e.g. after sterilization).
In the field of biotechnology, for example, often saturation is
measured and calibration is performed in the process medium for
reasons of sterility.
For other applications where concentration is measured (water
control etc.), calibration in air has proved to be useful.
Common combination: process variable / calibration mode
Measurement Calibration
Saturation Water
Concentration Air
The calibration procedures for these two common applications are
described on the following pages. Of course, other combinations
of process variable and calibration mode are possible.
Note:
When a 2-point calibration is required, the zero calibration should
be performed prior to saturation or concentration calibration, resp.
All calibration procedures must only be performed by trained
personnel.
65