Hach pHD sc Analog Differential pH/ORP Sensors Manuel D'utilisation page 12

Option Description
SET ISO At the isopotential point, the pH slope is
POINT independent of temperature. Most sensors have
an isopotential point of 7.00 pH (default), however
sensors for special applications may have a
different isopotential value.
LOG SETUP Sets the time interval for data storage in the data
log—5, 30 seconds, 1, 2, 5, 10, 15 (default), 30,
60 minutes.
RESET Sets the configuration menu to the default
DEFAULTS settings. All sensor information is lost.
4.4 Calibrate the sensor
4.4.1 About sensor calibration
Calibration adjusts the sensor reading to match the value of one or more
reference solutions. The sensor characteristics slowly shift over time and
cause the sensor to lose accuracy. The sensor must be calibrated
regularly to maintain accuracy. The calibration frequency varies with the
application and is best determined by experience.
A temperature element is used to provide pH readings that are
automatically adjusted to 25 °C for temperature changes that affect the
active and reference electrode. This adjustment can be manually set by
the customer if the process temperature is constant.
During calibration, data is not sent to the datalog. Thus, the datalog can
have areas where the data is intermittent.
4.4.2 pH calibration procedure
Sensors can be calibrated with 1 or 2 reference solutions (1-point or 2-
point calibration). Standard buffers are automatically recognized. Make
sure that the correct buffer set is used (refer to
options on page 15).
1. Put the sensor in the first reference solution. Make sure that the
sensor portion of the probe is fully immersed in the liquid
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2. Wait for the sensor and solution temperature to equalize. This can
3. Push the MENU key and select Sensor Setup, [Select Sensor],
4. Select the type of calibration:
Change calibration
(Figure 4).
5. If the passcode is enabled in the security menu for the controller,
Figure 4 Sensor in reference solution
take 30 minutes or more if the temperature difference between the
process and reference solution is significant.
Calibrate.
Option Description
2 point Use 2 buffers for calibration, for example pH 7 and
buffer pH 4 (recommended method). The buffers must be
from the buffer set that is specified in the Cal Options
menu (refer to
on page 15).
1 point Use 1 buffer for calibration, for example pH 7. The
buffer buffer must be from the buffer set that is specified in
the Cal Options menu.
2 point Use 2 samples or buffers of known pH value for
sample calibration. Determine the pH value of samples with a
different instrument.
1 point Use 1 sample or buffer for calibration. Determine the
sample pH value of samples with a different instrument.
enter the passcode.
Change calibration options