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TIPS
- How to determine if a pH probe is defective or at
the end of it's life:
- First, immerse the electrode in a pH 7.01 buffer
and use the mV (range key) to change the meter display to milli-volts.
- Next compare the reading to +/- 30.00mV. If the reading exceeds this
value, the electrode should be cleaned or replaced as it will be unstable.
An electrode in this condition will not be able to be reliably calibrated.
- How to "calibrate" an ORP probe:
- NO Calibration of the instrument
should be attempted
- Instead the ORP probe
should be checked for usability
- First,
immerse the electrode in an ORP standard such as 230mV or 470mV.
- Next
observe the ORP reading. If the reading is within 50mV of the standard,
it is a usable electrode.
- If the reading is outside those
limits, the probe should be replaced or cleaned
- Trying to calibrate the controller
without a milli-volt simulator is a bad idea. ORP is very different from pH.
- We do sell pH/ORP "calibrators".
These essentially are milli-volt simulators with displays showing pH or ORP
units directly. A knob control allows the user to output any value to
the BNC connected instrument.
- Decrease in slope of pH electrode:
- Usually caused by problems associated
with the glass. Oil, dirt, or salts which have built up on the surface
need to be cleaned. A "Cal-Check" Meter or controller will indicate this
condition. A value of 58.16mV is equal to a slope of 100%. Slopes
above 90% are normally considered acceptable.
- Increase in offset of the pH electrode:
- Typically caused by a clogged reference
junction or aging of the electrode.
- Cleaning of the electrode can partially
restore the electrode's offset closer to zero.
- Eventually, if the offset is too great,
the reading becomes unstable (see Tip #1)
- Reset of pH500 controller back to
factory default settings:
- Pressing the following key in sequence
will reset the controller. Remember to make note of how your controller
is setup prior to making this step.
- Press the four keys simultaneously (use
two hands):
- CFM key, SETUP key, → and CAL DATA.
- The controller is now reset and ready to
be reprogrammed for your application. Use the notes of your
configuration to reprogram the unit.
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