XIII.
A C C E S S O R I E S
A. Conductivity/TDS Standard Solutions
Your Ultrameter has been factory calibrated with the appropriate Myron L
Company NIST traceable KCl, NaCl, and our own 442 standard solutions.
Most Myron L conductivity standard solution bottles show three values
referenced at 25°C: Conductivity in microsiemens/micromhos and the
ppm/TDS equivalents based on our 442 Natural Water™ and NaCl
standards. All standards are within ±1.0% of reference solutions.
1. Potassium Chloride (KCl)
The concentrations of these reference solutions are calculated from data
in the International Critical Tables, Vol. 6. The 7000 µS is the
recommended standard. Order KCl-7000.
2. 442 Natural Water™
442 Natural Water Standard Solutions are based on the following salt
proportions: 40% sodium sulfate, 40% sodium bicarbonate, and 20%
sodium chloride, which represent the three predominant components
(anions) in freshwater. This salt ratio has conductivity characteristics
approximating fresh natural waters and was developed by the Myron L
Company over three decades ago. It is used around the world for
measuring both conductivity and TDS in drinking water, ground water,
lakes, streams, etc. The 3000 ppm is the recommended standard. Order
442-3000.
3. Sodium Chloride (NaCl)
This is especially useful in sea water mix applications, as sodium chloride
is its major salt component. Most Myron L standard solution labels show
the ppm NaCl equivalent to the conductivity and to ppm 442 values. The
14.0 mS is the recommended standard. Order NaCl-14.0.
B. pH Buffer Solutions
pH buffers are available in pH values of 4, 7 and 10. Myron L Company
buffer solutions are traceable to NIST certified pH references and are
color-coded for instant identification. They are also mold inhibited and
accurate to within ±0.01 pH units @ 25°C. Order 4, 7 or 10 Buffer.
C. pH Sensor Storage Solution
Myron L Storage Solution prolongs the life of the pH sensor. It is available
in quarts and gallons. Order SSQ or SSG.
D. Soft Protective Case
Padded Cordura® Nylon carrying case features a belt clip for hands-free
mobility. Model: UCC
® Registered trade mark of DuPont
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E. Replacement pH/ORP Sensor
Model RPR is gel filled and features a unique porous liquid junction. It is
user-replaceable and comes with easy to follow instructions.
F. Data Port
There is a 4 pin connector marked “Factory Use Only” on the bottom of
the Ultrameter. It is used to interrogate the instrument during final
inspection. Applications in the future for downloading recorded data are
being considered, but not implemented, as of this printing.
XIV.
TEMPERATURE COMPENSATION (Tempco)
of Aqueous Solutions
Electrical conductivity indicates solution concentration and ionization of
the dissolved material. Since temperature greatly affects ionization,
conductivity measurements are temperature dependent and are normally
corrected to read what they would be at 25°C.
A. Standardized to 25°C
Conductivity is very accurately measured in the Ultrameter by a method
that ignores fill level, electrolysis, electrode characteristics, etc., and uses
a microprocessor to perform temperature compensation. In simpler
instruments, conductivity values are usually assigned an average
correction similar to KCl solutions for correction to 25°C. The correction to
an equivalent KCl solution is a standard set by chemists. It standardizes
the measurements and allows calibration with precise KCl solutions. In
the Ultrameter, this correction can be set to other solutions or tailored for
special measurements or applications.
B. Tempco Variation
Most conductivity instruments use an approximation of the temperature
characteristics of solutions, perhaps even assuming a constant value.
The value for KCl is often quoted simply as 2%/°C. In fact, KCl tempco
varies with concentration and temperature in a non-linear fashion. Other
solutions have more variation still. The Ultrameter uses corrections that
change with concentration and temperature instead of single average
values. See Chart 1 on next page.
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