LaMotte 5 Series TDS Meter - Manual (Page 15)

Preparing the Meter for Calibration
Before starting calibration, be sure the meter is in the correct measurement
mode.
For best results, select a standard value close to the value of the sample that is
being measured. Alternatively use a calibration solution value that is
approximately 2/3 the full-scale value of the measurement range that is being
used. For example, in the 0 to 2000 µS conductivity range, use a 1413 µS
solution for calibration.
Calibrate all measurement ranges to ensure the highest accuracy throughout
the entire measurement range. Note that the CON 6/TDS 6 meter will not
accept calibration values less than 40 µS/cm (20 ppm). All new calibration
values will automatically override existing data.
If solutions with Conductivity lower than 100 µS/cm, or TDS lower than 50
ppm, are being measured the meter should be calibrated at least once a week
for optimum accuracy. If measurements are in the mid-ranges, and the probe is
washed with deionized water and stored dry, the meter can be calibrated once a
month. If measurements are taken at extreme temperatures, the meter should
be calibrated at least once a week.
Fresh conductivity standard solutions should be used during calibration. Do
not reuse standard solutions. They could be contaminated and affect the
calibration and accuracy of the measurements. Store solutions in a dry and cool
environment if possible.
Always rinse the probe with either deionized water or rinse solution before and
after each calibration/sample measurement to avoid cross-contamination. For
details refer to Probe Care and Maintenance.
NOTE: These meters are factory set to a temperature coefficient of 2.1% per
°C. For most applications this will provide good results.
To set the temperature coefficient to different value, see Temperature
Coefficient.
Also, see Appendix 3 - Calculating the Temperature Coefficient to determine
the appropriate temperature coefficient for any solution.
NOTE: The factory default value for normalization temperature is 25 °C. If a
value other than 25 °C is needed, see Normalization Temperature.
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