horiba U-51, Instruction Manual

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3 Basic Operation
48
14.
Calibration is finished when the message "Cal complete. ENT to manual cal menu."
appears. Press the ENTER key to return to the calibration parameter

ORP calibration
Note

If the prepared ORP standard solution is left in open air for one hour or more, the solution may be
transformed. For this reason ORP standard solution cannot be stored.
Calibrate within one hour of preparing the solution.

When measuring sample with low concentrations of oxidants and reductants after conducting an
operational check using a standard substance, the measured values may not stabilize or the
results of measurement might not be repeatable. If this is the case, start the measurement after
immersing the sensors in the sample water sufficiently.

Note that when measuring the ORP of solution with extremely low concentrations of oxidants and
reductants, such as tap water, well water, or water treated with purifying equipment, there may be
less responsiveness, repeatability, and stability, in general.

When alkaline ion water is left for 5 minutes, its ORP undergoes changes significantly. Always
measure alkaline ion water promptly.
1.
Fill a clean beaker with one bag of ORP standard powder No. 160-22 or No. 160-51.
Add 250 mL of deionized water and agitate the solution thoroughly (there will be
some excess quinhydrone (a black powder) that floats on the surface when
agitating the solution). Fill the transparent calibration cup to the reference line with
this standard solution.
2.
Wash the sensor probe 2 or 3 times in deionized water to remove any dirt, then
submerge the sensor probe in the transparent calibration cup.
3.
Press the control unit’s CAL key to set the calibration mode.
4. Press the down (  ) key to move the cursor to "Manual Calibration", then press the
ENTER key.
5.
In the parameter selection screen, move the cursor to ORP, then press the ENTER
key.