4.7 Relationship between Conductivity, Temp and TDS Values
A = These values measured by probe & sensors at operating steady state conditions.
B = This value is conductivity value multiplied by 0.7 (TDS in PPM)
C = This conductivity value temperature corrected to 25 degrees C / 77 degrees F.
D = This is measured TDS value entered into the system to effect a user “calibration.”
1. Conductivity measurement corrected at 2% per 1°C.
2. At 25°C TDS in ppm is calculated by multiplying the conductivity value by 0.7.
3. Both of the above multipliers are user variable to accommodate specific site conditions.
At the time of manufacture every TDS probe has buried in its electronics memory a “Calibration
Correction Coefficient” or CCC This is effected as set out below.
The TDS probe in a sampling vessel is immersed in a boiler water sample of a known TDS (i.e.
3500ppm for example). This is carried out at 25°C (77°F) which would give a reading in micro-
siemens of 5000. If the reading from the probe electronics does not agree with this a correction
multiplier or divider is implanted into this specific probes electronic memory. This is its own dedicated
CCC value.
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