Filter
Top Products
3
ORP CALIBRATION
1. After making an electrical connection between the
sensor and the instrument, obtain a standard solu-
tion of saturated quinhydrone. This can also be
made quite simply by adding a few crystals of quin-
hydrone to either pH 4 or pH 7 buffer. Quinhydrone
is only slightly soluble, therefore only a few crystals
will be required.
2. Immerse the sensor in the standard solution. Allow
1-2 minutes for the ORP sensor to stabilize.
3. Adjust the standardize control of the instrument to
the solution value shown in the table below. The
resulting potentials, measured with a clean plat-
inum electrode and saturated KCl/AgCl reference
electrode, should be within +/- 20 millivolts of the
value shown in the table below. Solution tempera-
ture must be noted to ensure accurate interpreta-
tion of results. The ORP value of saturated quinhy-
drone solution is not stable over long periods of
time. Therefore, these standards should be made
up fresh each time they are used.
4. Remove the sensor from the buffer, rinse, and
install in the process.
MAINTENANCE FOR ORP ELECTRODE
Electrodes should respond rapidly. Sluggishness, off-
sets, and erratic readings are indicators that the elec-
trodes may need cleaning or replacement.
1. To remove oil deposit, clean the electrode with a
mild non-abrasive detergent.
2. To remove scale deposits, soak electrodes for 30 to
60 minutes in a 5% hydrochloric acid solution.
3. ORP (metallic) electrodes should be polished with
moistened baking soda.
pH 4 Solution pH 7 Solution
Temp °C 20 25 30 20 25 30
mV Potential 268 264 260 94 87 80
ORP of Saturated Quinhydrone Solution (millivolts)