®
Advanced Water Quality Sensor
Conductivity
4
012-14325A
or on the interface select the
Conductivity (10x)
or
Conductivity (1x)
measurement,
depending on which electrode you are using.
Note: The 10x probe can be used to measure conductivity up to 100000
S/cm. The 1x probe
has one tenth of the range (up to 10000
S/cm) but ten times better resolution.
Measuring Conductivity
Before using the conductivity electrode, soak the end in distilled water for 5 to 10
minutes. Connect the electrode to the multi-sensor and start data collection. Immerse
the end of the electrode in the solution to be measured and wait for the reading to sta-
bilize. Rinse the electrode with deionized water before measuring a different solution.
The conductivity sensor has three ranges, which you select using the three buttons on
the multi-sensor. To select a range, push one of the buttons: for 0
S/cm to 1k (1000)
S/cm, for or 1k
S/cm to 10k
S/cm, or for 10k
S/cm to 100k
S/cm. Lights on the
buttons indicate which range is selected. To determine which range is appropriate,
look at the data (on a Graph display, for instance) while it is being collected; if the
measurement appears to be “railed” at the top of the selected range (1k
S/cm or 10k
S/cm), select the next higher range. You can push a button to change the range with-
out stopping data collection.
Note: The ranges specified above are for a 10x probe. Divide each range by 10 if you are using a
1x probe.
The conductivity electrode is sensitive to very low concentrations of dissolved solids,
so you will probably never measure a sample with a conductivity of zero. A reading
of 25
S/cm for “pure” water is typical. True pure water is difficult to obtain and
store. The table (right) lists typical conductivity values for common aqueous solutions
at 25 °C.
As a rule of thumb, to estimate total dissolved solids (TDS) in parts per million
(ppm), divide the conductivity in
S/cm by 2:
Conductivity Calibration
The conductivity measurement can be calibrated; however, for most applications cali-
bration is not necessary. Use a one-point calibration with a standard solution of
known conductivity. For instructions on preparing a standard solution, see Appendix
A. Refer to the SPARKvue/SPARK SLS, Capstone, or Xplorer GLX User’s Guide or
Online Help for calibration instructions.
Conductivity Electrode Maintenance And Storage
To ensure accurate and reproducible results, the electrode must be clean. Substances
on the electrode may contaminate the solution being tested and change the conductiv-
ity. To clean the electrode, dip the end into a detergent solution or dilute nitric acid
(1%) and stir for three minutes, then rinse with deionized water.
For storage, dry the electrode and return it to its box. Before use, soak the electrode in
distilled water for at least 5 minutes.
Solution
Conduc-
tivity
(
S/cm)
Ultra-
pure
Water
0.05 to
0.75
Drinking
Water
50 to
1500
Ocean
Water
~53000
TDS (ppm)
Conductivity
S/cm
2
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