Nova-Tech SALT 6+ - Manual (Page 34)

Instruction Manual COND 6+, TDS 6+, SALT 6+
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Conductivity and Temperature
Conductivity in aqueous solutions reflects the concentration, mobility, and charge of the
ions in solution. The conductivity of a solution will increase with increasing temperature,
as many phenomena influencing conductivity such as solution viscosity are affected by
temperature.
The relationship between conductivity and temperature is predictable and usually
expressed as relative % change per degree centigrade. This temperature coefficient (%
change per degree) depends on the composition of the solution being measured.
However, for most medium range salt concentration in water, 2% per degree works well.
Extremely pure water exhibits a temperature coefficient of 5.2%, and concentrated salt
solutions about 1.5%.
Since temperature affects the conductivity measurement so profoundly, usual practice is
to reference the conductivity to a standard temperature
⎯ typically 25 °C. Select 20 °C
or 25 °C as the normalization temperature in advanced setup.
Enter the temperature coefficient which best suits your sample and use an ATC probe to
automatically temperature compensate back to the chosen reference temperature.
10. CALIBRATION TIPS
You only need one calibration for measurement throughout the entire range of the
meter. If a range was not calibrated, the meter automatically detects the closest range
calibrated and uses that calibration information. However, only the ranges that were
calibrated have maximum accuracy.
If you are measuring in ranges near to or greater than 20 mS/cm (10 ppt), or near to or
lower than 100 µS/cm (50 ppm), suggested calibration frequency is at least weekly.
If you are measuring in the mid-ranges and you wash the probe in deionized water and
store it dry, suggested calibration frequency is at least monthly.
Wet the probe for 10 minutes before calibrating or taking readings to saturate the probe
surface and minimize drift. If you take measurements at extreme temperatures, calibrate
the meter at least once a week.
You should only use the probe specified for these meters. These probes have a built-in
temperature sensor. If you use a different probe without a temperature sensor, you must
measure the solution temperature separately and manually enter the solution
temperature.