Hach-Lange NH4D sc Ammonium Sensor - Manual (Page 22)

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Operation
4.6 Calibration
The membranes on the ion-selective electrodes are not 100%
selective due to other substances that may affect the
measurement. Perform a matrix correction to compensate the
influences of other ions on the ammonium ISE electrode.
Potassium has the largest interference effect on the ammonium
membrane. This problem is compensated in the NH4D sc sensor
using the integrated potassium electrode.
CARTRICAL TM is a compact sensor cartridge with 3 electrodes,
which are perfectly factory calibrated to each other.
Cross sensitivities between ammonium and potassium are
automatically eliminated. Solids do not interfere with the
measurement. Due to matrix effects calibration and validation can
not be performed with standard solutions. A matrix correction can
be carried out quickly and easily at any time.
Important Note: Matrix correction must not be performed until the
sensor has been immersed in the process longer than 12 hours.
12 hours is the mimimum amount of time required for the ISE
membranes to adapt to the waste water matrix.
The 12 hours is required to allow the sensor cartridge to adapt to
the process.
4.6.1 Sensor code calibration
When activating a new sensor cartridge or during initial calibration,
the sensor code must be entered. The default sensor code is
FYM7N725PGK7I0FF. With this code, the sensor is ready for
operation. To meet published specifications, enter the individual
sensor code for the specific CARTRICAL cartridge.
Enter the sensor cartridge's sensor code to accept the CARTRICAL
calibration. The sensor code is a 16 character code (letters and
numbers) and will be supplied with the sensor cartridge certificate.
The code contains the factory calibration for the sensor cartridge,
which includes a multi-point ammonium and potassium calibration
and the cross sensitivity of potassium on ammonium and vice
versa.
When the code is entered, the sensor is completely calibrated. It is
recommended to perform a matrix correction to correct the
cartridge on the specific matrix.
To change the sensor code:
1. Select SENSOR SETUP>NH4D SC>
CALIBRATE>CAL.CONFIG.>SENSORCODE
2. Enter the 16 character sensor code.
3. Press ENTER to confirm and activate the sensor code.
The day meter is set to zero.
All old calibration data are now overwritten with the new calibration
data from the sensor code. The sensor code data are checked by
the system. If an error is indicated, check the sensor code and if
necessary repeat the entry of the sensor code.