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NitraLyt
®
700 IQ Calibration and measuring
4 - 1 ba75397d03 12/2004
4 Calibration and measuring
4.1 Calibration
4.1.1 General information
Why calibrate? When a nitrate electrode is operated its characteristic curve changes
with the course of time. The characteristic curve is generally character-
ized by the slope and the axis intercept. The characteristic curve is the
base for calculating the measured value from the electrode voltage.
With calibration, the current characteristic curve parameters are deter-
mined as follows:
!
With all calibration procedures, i. e. 1-point and 2-point procedures,
the change of the axis intercept is determined ("drift potential").
!
All two-point calibration procedures additionally determine the
slope.
Why calibrate? Calibrate during the initial commissioning, after exchanging an elec-
trode and at regular intervals (depending on the application).
Calibration log and
calibration history
The calibration history contains the calibration log of the initial and last
of the following calibrations. You can call up the calibration history via
the
Calibration history of selected sensor display option.
Citation form There are two common citation forms for the specification of nitrate
contents in a solution. The citation form, NO3, specifies the nitrate con-
tent (NO
3
-
). The citation form, NO3-N, specifies the amount of nitrate
nitrogen only. You can select the required citation form in the settings
for the sensor.
If the citation forms do not correspond, you can carry out the conversion
yourself.
1 mg/l NO3 = 0.226 mg/l NO3-N.
1 mg/l NO3-N = 4.427 mg/l NO3.
Note
Ordering information on nitrate standard solutions can be found in sec-
tion 6.2.