Specifications

Conductivity/
TDS/Salinity
About Conductivity/TDS/
Salinity Measurement
Conductivity Cells
Most conductivity meters have a 2-cell electrode available in either
dip or flow-through styles. The electrode surface is usually platinum,
titanium, gold-plated nickel, or graphite. The 4-cell electrode uses a
reference voltage to compensate for any polarization or fouling of the
electrode plates. The reference voltage ensures that measurements
indicate actual conductivity independent of electrode condition,
resulting in higher accuracy for measuring pure water.
The Eutech EC620165 4-cell conductivity electrode (cell constant
K=1.0) with in-built ATC and DIN connector is available for use
with the bench meters CON 1500, PC 6000, PC 6500 and PCD 6500.
ECCONSEN9203J 4-cell conductivity electrode with ATC and 3 m
cable is available for COND 600, COND 610, PCD 650 and CD 650
handheld meters.
Important Features to Consider in a Conductivity Meter
• Auto-Ranging
Meter automatically selects the appropriate range for measurement.
There is no need to change the dial, multiply values on the display,
or turn the potentiometer.
• Temperature Compensation
A cell with built-in temperature sensor allows the meter to make
adjustments to the conductivity or TDS readings based on changes
in solution temperature.
• TDS Conversion Factor
When a solution does not have a similar ionic content to natural water
or salt water, then a TDS conversion factor is needed to automatically
adjust the readings.
• Adjustable Temperature Coecients
The TDS of certain samples, such as alcohols and pure water, are
affected by changes in temperature. An adjustable temperature
coefficient allows the user to compensate for temperature changes
on the solution being measured.
• Adjustable Cell Constant
Adjusts the reading on the display to reflect use of a cell with a
constant other than k=1.0 cm
-1
.
Eutech’s wide range of conductivity meters incorporates these
features for consistent, accurate and reliable measurements.
Figure 1
C = G x (L/A)
If the cell constant is 1 cm
-1
, the specific conductivity is the same as
the measured conductivity of the solution. Although electrode shapes
vary, an electrode can always be represented by an equivalent
theoretical cell.
Conductivity Temperature Compensation
Conductivity measurements are temperature dependent. The degree to
which temperature affects conductivity varies from solution to solution
and can be calculated using the following formula:
Gt = Gt
std
{1 + α(T-T
std
)}
where:
Gt = Conductivity at measured Temperature T in °C;
Gt
std
= Conductivity at Reference (Normalisation) Temperature T
std
in °C;
α = Temperature Coefficient of solution at T
std
in °C;
T
std
= Reference or Normalisation Temperature in °C
All meters have either fixed or adjustable automatic temperature
compensation referenced to a standard temperature – usually 25 °C.
Most meters with fixed temperature compensation use α of 2 % per °C
(the approximate α of NaCl solutions at 25 °C). Meters with adjustable
temperature compensation let you to adjust the α to more closely
match the α of your measured solution.
Conductivity Meter Calibration and Cell Maintenance
Conductivity meters and cells should be calibrated to a standard
solution before using. When selecting a standard, choose one that has
the approximate conductivity of the solution to be measured.
A polarized or fouled electrode must be cleaned to renew the active
surface of the cell. In most situations, hot water with a mild liquid
detergent is an effective cleanser. Acetone easily cleans most organic
matter, and chlorine solutions will remove algae, bacteria or molds. To
prevent cell damage, abrasives or sharp objects should not be used to
clean an electrode. A cotton bud works well for cleaning but care must
be taken not to widen the distance of cell.
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