Hanna Instruments HI 98188 Instruction Manual page 26

Usp compliant ec, tds, nacl, resistivity, temperature meter

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Enlarged version

EC EC EC EC EC CALIBRATION

CALIBRATION

It is recommended to calibrate the instrument frequently, especially if high

accuracy is required.

The EC range should be recalibrated:

• Whenever the EC electrode is replaced.

• At least once a week.

• Before USP measurement.

• After testing aggressive chemicals.

• When calibration alarm time out is expired - "CAL DUE" blinks (if feature

is enabled in SETUP).

• If "Outside Cal Range" message blinks during EC measurement (the

measurement range is not covered by current calibration, if feature is

enabled in SETUP).

Note: TDS and Resistivity readings are automatically derived from the EC

reading and no specific calibration is needed.

PROCEDURE

HI 98188 instrument offers a choice of 7 memorized standards (0.00 mS/cm,

84.0 mS/cm, 1.413 mS/cm, 5.00 mS/cm, 12.88 mS/cm, 80.0 mS/cm and

111.8 mS/cm).

For accurate EC measurements, it is recommended to perform a calibration in

maximum allowed points. However, at least a two-point calibration is suggested

(offset calibration in 0.00 mS and one in any other calibration standard).

The instrument will automatically recognize the standards and skip the stan-

dard used during calibration.

• If a five-point calibration is performed, one of the points must be 0.0 mS (offset).

• Pour small quantities of selected standard solutions into clean beakers. For

accurate calibration use two beakers for each standard solution, the first one

for rinsing the electrode and the second one for calibration.

• Remove the protective cap and rinse the electrode with some of the

standard solution to be used for the first calibration point.

FIVE-POINT CALIBRATION

• It is better to perform the first point calibration as offset calibration.

• Tap the probe repeatedly to remove any air bubbles that may be trapped

inside the sleeve.

• For offset (zero) calibration, just leave the dry probe in the air.

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