LTH Electronics HPT63, Руководство по эксплуатации

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10 Calibration
30
Check the temperature of the solutions. From the documentation supplied with the
solutions, determine the true values of the solutions at the measured temperatures.
Use these (true) values for calibration purposes.
Note: Appendix D – Buffer Solutions lists typical buffer solution pH values at various
temperatures.
Prepare a beaker of clean, preferably de-mineralised water for washing the sensor
between measurements.
10.4.2 Procedure
For each prepared buffer solution, carry out the following procedure:
1.
Wash sensor in de-mineralised water.
2. Insert the sensor in the prepared buffer solution.
3. From the Sensor Buffer or Sensor Slope page, press the key. The screen
will display ‘Are you sure?’.
4. Press to confirm (or any other key to abandon calibration). On pressing
, the display will show the sensor reading.
5. Use the and keys to set the reading to the known true (temperature-
compensated) value of the solution.
6. Press to confirm the correct reading. The display will show the buffer or
slope calculated by the instrument (where 0 pH and 100% are the default
values).
7. Rinse the sensor in clean water.
10.5 Redox Sensor Calibration
For the Redox setup only the offset (zero) can be adjusted - by
±
200mV. To adjust
the Redox offset, with the sensor units in mV, select the Sensor Buffer menu item
from the Calibration menu.
10.5.1 Redox Standards
Unlike pH electrodes, the Redox electrode’s slope does not change. Nevertheless,
incorrect Redox potentials may occasionally be measured and the cause of these
errors is usually a contaminated platinum (Pt) surface, or a contaminated or plugged
reference junction.
Standard Redox solutions are available from various sources at potentials of 385 mV
(from LTH), 124, 200, 250, 300, 465, 600 and 650 mV. It is possible to make up
standards as detailed in Appendix C – Redox Solutions.