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9. Conductivity Measurement
9.1 How to Measure Conductivity, TDS, Salinity, and Resistivity
Short press
to turn on the tester. Rinse the probe in pure water, shake off excess water. Insert
the probe in your sample solution, make a quick stir and hold still. Record the reading when it is
stabilized
(
comes up and stays on screen). Press
to switch from conductivity to TDS,
salinity, and resistivity. Or if you turn on the Auto-Hold function (refer to Section 13.2 (2)), the
reading will be automatically locked when it's stable. Short press
to cancel the Auto-Hold and
keep measuring.
9.2 Unit Conversion
a. 1000 µS = 1 mS = 1 EC (In conductivity mode, the unit will automatically turn from µS to mS if the
reading is greater than 1999 µS, meaning you will only see 2.XX mS instead of 2XXX µS)
b. 1000 ppm = 1 ppt (In TDS mode, the unit will automatically turn from ppm to ppt if the reading is
greater than 999 ppm, meaning you will only see 1.XX ppt instead of 1XXX ppm)
c. The TDS and Salinity values are converted from the conductivity values via a certain conversion
factor. TDS and conductivity is linear related, and its conversion factor is 0.40 to 1.00. Adjust the
factor in parameter setting P13 based on the requirements in different industries. The factory
default setting is 0.71.
d. Salinity and conductivity is linear related, and its conversion factor is 0.5.
e. Conversion Example: if conductivity measurement is 1000µS, then the default TDS measurement
will be 710 ppm (under the default 0.71 conversion factor), and the salinity be 0.5 ppt. If TDS
conversion rate is changed to 0.5, then the TDS measurement will be 500 ppm.
9.3 Temperature compensation factor
The default setting of the temp. compensation factor is 2.0%/˚C. User can adjust the factor based
on test solution and experimental data in parameter setting P10. The following table is some
common examples for setting up the temp. compensation factor.
Solution
Temperature
compensation factor
Solution
Temperature
compensation factor
NaCl
2.12%/˚C
10% Hydrochloric acid
1.32%/˚C
5% NaOH
1.72%/˚C
5% Sulfuric acid
0.96%/˚C
Dilute ammonia
1.88%/˚C