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Section 4 Calibration
4.1 Calibration intervals
The MP Series meters are designed to not require frequent calibration. Calibration
is recommended about once per month with conductivity or TDS solutions. Check
the calibration with pH solution twice per month. Some applications may require
calibration frequencies to differ from these suggested guidelines.
4.2 Calibration limits
The MP Series meters have built in calibration limits. A nominal “FAC” value is an
ideal value stored by the factory. Attempts to calibrate too far (±10% or ±1 pH unit)
from this value causes the displayed value to be replaced with “FAC”. If the
CAL/MCLR key is pushed, the value is accepted, and the original default factory
calibration for this measurement is shown. The need to calibrate so far out that
“FAC” appears indicates a procedural problem, incorrect standard solution, a very
dirty cell cup or an aging pH/ORP sensor.
4.3 Calibration records
To minimize calibration efforts, keep records. If the calibration adjustments are
minimal, calibration can occur less often. Record the following information:
• Record changes in conductivity in percentages.
• Record changes in pH calibration in pH units.
• Conductivity cell calibration is purposely limited to
±10%. Changes beyond that
indicate damage, not drift.
• Calibration changes are limited to
±1 pH unit. Changes beyond that indicate the
end of the sensor’s lifetime and replacement is recommended.
4.4 Calibrate the meter
1. Push the measurement key for the parameter to be calibrated.
2. Push CAL/MCLR.
3. Measuring continues. The CAL icon is on. This indicates that calibration can
occur now.
4. Push UP/MS or MR/DOWN to change the reading to the known value.
5. Calibration for each of the four solution types can be performed in either
conductivity, mineral/salt or TDS mode.
Note: The number of steps to calibrate depends on what is to be calibrated.
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