User guide
XI. ACCESSORIES
A. Conductivity/TDS Standard Solutions
Your AR1 has been factory calibrated with the appropriate Myron L
Company NIST traceable standard solution. 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 1800 µS or 18,000 µS are
the recommended standards. Order KCl-1800 or KCl-18,000.
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 1500 ppm or 15,000 ppm are the recommended
standards. Order 442-1500 or 442-15,000.
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. Soft Protective Case
Padded Cordura
®
Nylon carrying case features a belt clip for hands-free
mobility. Order Model: UCC ® Registered trade mark of DuPont
C. pH Buffer Solutions
For your Myron L pH instruments; 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.
XII. 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 AR1 by a method that
ignores fill level, electrolysis, electrode characteristics, etc., and uses a
unique circuit 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
recognized for stability. In the AR1, this correction can be set to either
KCl, NaCl or 442 to best match your 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 AR1 uses corrections that
Chart 1
1.500%
1.600%
1.700%
1.800%
1.900%
2.000%
2.100%
2.200%
2.300%
2.400%
2.500%
Temperature
0 5 10 15 20 25 30 35 40 45 50 55 60
KCl % / °C
% / °C
14 15