Thermo Orion Star, User Manual

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Thermo Electron Corporation IX-2 Orion Star Series Meter
Conductivity Technique
• Conductivity TDS Factor: Total Dissolved Solids (TDS) refers to the dissolved
inorganics in a solution . These dissolved inorganics will carry a current and
will be reflected as a conductivity reading . Since a relationship can be shown
between conductivity and TDS, a conductivity reading can be used as an
estimation of the presence of inorganics .
• The standard method of determining TDS (Total Dissolved Solids) is by
evaporating the sample to dryness at 180 ˚C and weighing the residue . After
evaporating the sample, one would have to calculate a specific “factor” for
the solution by taking the TDS value obtained in weighing and dividing it by
the conductivity of the sample . This factor would then be multiplied by the
subsequent conductivity readings to obtain the TDS value of the sample as
referenced in Standard Methods for Water and Wastewater .
• This Meter allows the operators to enter their own TDS factor for the
calculation of the TDS value in mg/L, with a selectable range from 0 .01 to
10 .00 and a default value of 0 .49 . The default value for TDS factor on the
meter is 0 .49, which is a reasonable estimate of a TDS factor for natural
water applications .
• Auto-Calibration for conductivity uses a default cell constant to determine the
value of the conductivity standard . In order for the instrument to Auto-recognize
a conductivity standard it must know the cell constant within a factor of 3 . So
the meter needs a nominal cell constant for the probe being used . If the real
cell constant was 1 .0 then having an estimate of any value between 0 .3 and 3 .0
would be sufficient to determine which standard was being used and therefore
determine the standards temperature corrected value for calibration .
• The instrument Auto-recognizes Orion conductivity standards
1413 μS/cm,100 μS/cm, and 12 .9 mS/cm only .