7.6
ORP Calibration
The ORP scale of the SP-710B depends on the ORP scale of the calibration standard. For example, if the
value of 220 mV for the common Zobell’s standard at 25 °C is entered in the above calibration, the ORP
value reported by the SP-710B after calibration is referenced to the Ag/AgCl(3M KCl) scale. This is because
the value of 220 mV is based on the Ag/AgCl(3M KCl) reference electrode. If the value entered in the above
calibration is 429 mV, the ORP value reported by the SP-710B is referenced to the SHE, because the value
of 429 mV at 25 °C for the Zobell’s standard is SHE based.
The values in the following table can be used to convert the Ag/AgCl reference electrode-based ORP value
to the SHE-based ORP value. To obtain the SHE-based ORP value, add the number in the table to the cor-
responding Ag/AgCl reference electrode-based value. To use the table, the temperature of the standard
solution measured by the SP-710B must be used.
Table 3.
Temperature °F (°C)
*
Ag/AgCl (1M KCl)
Ag/AgCl (3M KCl)
Ag/AgCl (saturation KCl)
68 (20)
+234
+213
+202
77 (25)
+231
+209
+199
86 (30)
+228
+205
+196
*
Use the temperature measured by the SP-710B.
Follow the steps below to carry out an ORP calibration:
1. Power on the SP-710B by pressing
.
2. Rotate the pH/ORP cell seal to touch the front face of the module as seen in Figure 5. This is to power
on the module. The indicator light of the module will be green and flashing when powered on. After
the module is turned on, the seal can be positioned anywhere desired.
*
NOTE
*
If the module battery capacity is low, the indicator light will flash red .
3. Press
Calib
(
) as needed to highlight
ORP
in the selection menu.
4. Press
to launch the
ORP CALIBRATION
screen.
5. The main module of the SP-710B will automatically connect after the pH/ORP module has been pow-
ered up.
6. Use
+
(
) and
-
(
) to adjust the ORP value to match the ORP standard used (Figure 29).
7. Press
Calib
(
). The message “
Calibration Success
” will appear on the display (Figure 30).
8. Calibration is now complete. Long press
Calib
(
) to return to measurement mode.
SP-710B User Manual
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