41
Position the sachet to ensure sensor membrane and ceramic junction are completely immersed in
solution. A value close to 100 ppm and the message “Not ready...” will be displayed.
• When the reading is stable, the countdown timer will count down until the display shows the
“Ready” message.
• Press <Confirm> to accept the calibration.
• After the second calibration point is confirmed the display shows the following messages: “Storing”
and “Calibration completed”.
• Press <OK> to return to the Calibration menu.
• Press <Measure> to return to the measurement screen.
Note: The ISE calibration mode can be exited at any time, by pressing the ESC key.
The “ORP calibration” allows the user to perform a single point custom calibration (relative mV) or
to restore the factory calibration.
The Oxidation‑Reduction Potential (ORP), displayed in mV, is the voltage that results from the diffe‑
rence in potential between the platinum ORP sensor and the silver/silver chloride reference electrode.
ORP values are not temperature compensated, although ORP values can change with temperature
(e.g. reference electrode potential changes, sample equilibrium changes). It is important to report
ORP values together with the reference electrode used and the temperature.
The inert platinum ORP surface provides an electron exchange site with the sample (or standard)
and its surface. The electron exchange is typically very fast in well‑poised solutions (standards for
example), but may be more lengthy in natural water samples.
Calibration is typically not required for a new ORP sensor, but the process does establish a baseline
that can be used as a comparison for future validations.
Calibration is used to compensate for changes due to contamination of the platinum surface and drift
in the reference electrode.
A relative mV calibration can also be made to remove the voltage attributable to the Ag/AgCl reference
electrode (to display the ORP versus a SHE (standard hydrogen electrode)). This is really an arithmetic
correction and is correct only at the standard temperature. For example, HI7022 reads 470 mV at
25 °C versus the Ag/AgCl reference. The ORP mV versus a SHE would be 675 mV. (add 205 mV to
the observed value).
ISE CALIBRATION
ORP CALIBRATION
To Next Page
Loading...
