Hach-Lange DR 2800 eco - Manual (Page 72)

70
Advanced Operations
Calibration
A method is calibrated by determining the absorbance values of
several standard solutions of known concentration.
There are a number of ways of obtaining a calibration curve:
After selecting the calibration mode, press Next.
Calibration values (Enter values):
Entering concentration/absorbance
1. Press Enter Values and press Next.
2. To enter the standard concentrations and corresponding
absorbance values in the displayed table, press the "+" symbol.
Use the alphanumeric keypad to enter the values.
Press OK and enter the corresponding absorbance value.
Press OK.
The entered data are displayed in the table. Repeat the
sequence for each data point you need to enter.
3. If you want to change a value in the table, activate the
appropriate line, press the unit key (e.g. mg/L) or Abs and
enter the changed value via the alphanumeric keypad.
Table 10 Calibration mode
Mode Descriptions
Enter values
A calibration table is created by entering the concentration values and the absorbance values of
the corresponding standard solution. The absorbance values are plotted against the
concentrations of the standard solutions in a diagram. The calibration curve is displayed as a
graph.
Read Standards
A calibration table is created by entering the concentration values of the standard solutions and
then measuring the solutions to determine the corresponding absorbance values. The
absorbance values are plotted against the concentrations of the standard solutions in a diagram.
The calibration curve is displayed as a graph.
Enter Formula
If the calibration curve can be determined from the mathematical relationship between
concentration and absorbance by linear regression, or some other curve fitting is possible, the
corresponding formula can be selected (linear, 2nd or 3rd order polynomial) from a list and the
appropriate factors can be entered.