Myron L 4P (includes Addendum 10-01) User Manual

Page 16

XVII.

GLOSSARY

Anions -

Negatively charged ions.
See Solution Characteristics, pg. 26.

Algorithm -

A procedure for solving a mathematical problem.
See Temperature Compensation and TDS Derivation,
pg. 27.

TDS

Total Dissolved Solids or the Total Conductive Ions
in a solution. See Conductivity Conversion to TDS,
pg. 26.

Tempco -

Temperature Compensation
See Temperature Compensation, pg. 23.

USER -

A mode of operation that allows the instrument user
(operator) to set a tempco and/or a TDS factor for their
specific solution type. See Temperature Compensation,
pg. 23 and Temperature Compensation (Tempco) and
TDS Derivation, pg. 27.

For details on specific areas of interest refer to Table of Contents.

Another solution would have a different tempco because of its ionization
activity. And, that tempco may be a little different at a different
concentration or temperature. This is why the Ultrameter uses
mathematically generated models for known salt characteristics that vary
with concentration and temperature.

B. Finding the Tempco of an Unknown Solution

One may need to measure compensated conductivity of some solution
unlike any of the 3 standard salts. In order to enter a custom fixed tempco
for a limited measurement range, enter a specific value through the
“USER” function. The tempco can be determined by 2 different
methods:

Heat or cool a sample of the solution to 25°C, and measure its
conductivity. Heat or cool the solution to a typical temperature
where it is normally measured. After selecting USER function,
set the tempco to 0 %/°C as in Disabling Temperature
Compensation, pg. 12 (No compensation). Measure the new
conductivity and the new temperature. Divide the % decrease
or increase by the 25°C value. Divide that difference by the
temperature difference.

Heat or cool a sample of the solution to 25°C, and measure its
conductivity. Change the temperature to a typical measuring
temperature. Set the tempco to an expected value as in User
Programmable Tempco, pg. 11. See if the compensated value
is the same as the 25°C value. If not, raise or lower the tempco
and measure again until the 25°C value is read.

C. Finding the TDS Ratio of an Unknown Solution

Once the effect of temperature is removed, the compensated
conductivity is a function of the concentration (TDS). There is a ratio of
TDS to compensated conductivity for any solution, which varies some
with concentration. The ratio is set during calibration in USER as in User
Programmable Conductivity to TDS Ratio, pg. 12. A truly unknown
solution has to have its TDS determined by evaporation and weighing.

Then the solution whose TDS is now known can be measured for

conductivity and the ratio calculated. Next time the same solution is to be
measured, the ratio is known.