SWITCHING MODES
Electrical Conductivity (EC) and Total Dissolved Solids (TDS) Overview: While EC and TDS are often used synony-
water sample. TDS refers to the total amount of substances dissolved in the water other than the pure H2O. The only
average person, we can estimate the TDS level by measuring the EC of the water. Every digital TDS meter in the world
EC to TDS using a scale that mimics the charge of that water type. The following are the most common water samples,
and for the COM-100, each has its own non-linear conversion factor:
KCl: Potassium Chloride is the international standard to calibrate instruments that measure conductivity. The COM-100
is factory calibrated with a 1413 µS (micro-Siemens) KCl solution. The meter’s default mode is EC-µS.
442TM : Developed by the Myron L Co., 442TM simulates the properties of natural water (rivers, lakes, wells, drinking water,
etc.) with a combination of 40% Sodium Bicarbonate, 40% Sodium Sulfate and 20% Chloride.
NaCl: Sodium Chloride is used in water where the predominate ions are NaCl, or whose properties are similar to NaCl,
such as seawater and brackish water.
àMeasurements in EC (µS or mS) do not have a conversion factor.
standard temperature for EC and TDS readings is 25oCelsius. Without compensation, the EC and TDS readings will
increase when the temperature is greater than 25oand decrease when the temperature is lower than 25o. The COM-100
is equipped with Automatic Temperature Compensation (ATC). The meter will automatically adjust the reading to what
it would be at 25oµS or mS) use the
For additional information on TDS, please visit www.tdsmeter.com and click on “What is TDS?”.
Defaults: EC (µS) and the temperature reading in Celsius.
Switching EC and TDS Modes:
µS
(micro-Siemens) or mS (milli-Siemens). 1000 µS = 1 mS.
ppm (parts per
million) or ppt (parts per thousand), with 2 selectable conversion factors 0.7 or 0.5.
1000 ppm = 1 ppt.
To change the EC or TDS mode:
1. With the power on, press and hold the‘HOLD/MODE’ button. The display will cycle
through the modes in the order listed below. NOTE – the scale icons appear above the
measurement reading, and the conversion factor icons appear below the measurement
reading. Since EC does not use a conversion factor, the conversion factor icons will not
appear for the EC modes.
a. EC – µS
b. EC – mS
c. TDS – ppm (442TM) 0.7
d. TDS – ppm (NaCl) 0.5
2. When the meter displays the desired selection, release the ‘HOLD/MODE’ button.
3. The meter is now ready for use in your selected mode. The meter will keep this
setting until changed again.
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Example: mS mode
Example: ppm-442 mode
