37
MODEL SOLU COMP II
SECTION 6.0
CALIBRATION
SECTION 6.0
CALIBRATION
6.1
INTRODUCTION
6.2 CALIBRATING
TEMPERATURE
6.3
CALIBRATION - DISSOLVED OXYGEN
6.4
AUTO CALIBRATION - pH
6.5
MANUAL CALIBRATION - pH
6.6
STANDARDIZATION - pH
6.7
ENTERING A KNOWN SLOPE - pH
6.8
ORP CALIBRATION
6.1 INTRODUCTION
The Calibrate Menu allows the user to calibrate sensor 1 (dissolved oxygen) and sensor 2 (pH or ORP). The tem-
perature response of each sensor can also be calibrated.
Oxygen sensors require periodic full-scale calibration. Automatic air calibration is standard. The user simply sus-
pends the sensor over a container filled with water. When readings are stable, the analyzer automatically calcu-
lates the equilibrium solubility of atmospheric oxygen in water and calculates the sensitivity (sensor current divid-
ed by oxygen concentration). The sensor can also be calibrated against a referee instrument.
New oxygen sensors must be zeroed before being placed in service. Sensors should also be zeroed every time
the electrolyte solution is replaced. Zeroing involves placing the sensor in an oxygen-free environment until the
sensor current drops to its lowest stable value.
For pH sensors, two-point buffer calibration is standard. In auto calibration the analyzer calculates the pH of the
buffer from the nominal value entered by the user and does not accept calibration data until readings are stable.
In manual calibration the user enters buffer values and judges when readings are stable. The pH reading can also
be standardized, that is, forced to match the reading from a referee instrument. Finally, if the user knows the elec-
trode slope (at 25°C), he can enter it directly.
The ORP calibration is a single-point calibration against an ORP standard.
