88
89
Make sure the instrument and probe has been calibrated in conductivity mode before taking resistivity
measurements.
DIRECT MEASUREMENT
To measure the resistivity of a sample using the
Direct
reading
mode:
• Press
and then
to select resistivity measure
mode.
• Select the
Direct
reading mode (see
Resistivity
Setup
section).
• Proceed the same as for the conductivity measurement (see
Conductivity Measurement
section).
DIRECT/AUTOHOLD MEASUREMENT
To measure resistivity of a sample using the
Direct/AutoHold
reading mode:
• Select the
Direct/AutoHold
reading mode (see
Resistivity
Setup
section).
• Proceed the same as for the conductivity measurement. (see
Conductivity Measurement
section).
RESISTIVITY MEASUREMENT
Stage 3
- this is an off-line test that studies the pH and CO
2
.
If the water sample has failed Stage 1 and Stage 2 tests, Stage 3 testing must be conducted.
To perform this test use Channel 1 in pH mode. Have a
calibrated pH sensor installed.
Note:
A temperature bath at 25.0 ±1 °C is required for this
measurement.
• Take the water sample from the stage 2 test and increase its
ionic strength for a pH measurement at 25 °C.
• Use 100 mL of Stage 2 water and add 300 µL saturated KCl to
the sample.
• Calibrate a pH sensor in pH 4.01 and pH 6.862 (or 7.01)
buffers.
• Thermally equilibrate the sample to 25.0 ±1 °C.
• Measure sample with the calibrated pH sensor.
• The pH of sample must be between 5.0 and 7.0 pH.
• Record the pH and round it to the nearest 0.1 pH.
• Find the measured pH and corresponding conductivity in the stage 3 table below.
• Compare the conductivity value determined in stage 2 to the conductivity value found in the stage 3 table.
• If the stage 2 conductivity is lower than the conductivity from the table below, the sample has meet the
USP requirements. Otherwise, the water didn’t meet the USP requirements.
Note:
If the Stage 2 water fails, the meter automatically changes to pH and starts Stage 3 evaluation.
Having 25 °C sample with added ionic salt is required. At the conclusion at Stage 3 evaluation, press
to store a report of the results. The report may be printed using
HI 92000
software.
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