EC500 Datasheet, PDF (9/14 Pages) Extech Instruments Corporation. – pH/Conductivity / TDS / Salinity / Temperature Meter

Calibration - Conductivity
Meter accuracy verification should be performed on a periodic basis. Once per month is
the recommended cycle for normal use. If calibration is required, a conductivity
standardizing solution must be obtained. The meter can be calibrated in any or all of the
three ranges. Standardizing solutions of 84µS/cm, 1413µS/cm or 12.88mS/cm
(12,880µS/cm) are used for the automatic calibration recognition procedure. No other
calibration values are permitted.
Calibration is always done in conductivity mode. Since salinity and TDS values are
calculated from conductivity values, this procedure also calibrates the salinity and TDS
ranges.
1. Fill a sample cup with the standardizing solution.
2. Turn the meter ON and insert the electrode into the solution. Tap or move the
electrode in the sample to dislodge any air bubbles.
3. Press and hold the CAL/RECALL button (approximately 2 seconds) until “CAL”
appears in the lower (temp) display. The main display will start flashing.
4. The meter will automatically recognize and calibrate to the standardizing solution.
The display will briefly indicate “SA”, End and then return to the measurement mode
after a calibration.
Note: The “SA” will not appear if the calibration fails.
5. The “range calibrated” symbol will appear in the display for each range that is
calibrated during that power on cycle.
Low range, 84µS/cm
Medium range, 1413µS/cm
High range, 12.88mS/cm (12,880µS/cm)
Note: Each time the calibration mode is entered all calibration symbols on the display are
cleared, but only the calibration data for the currently calibrated range is replaced. The
other two ranges keep the existing calibration data, just the symbols are removed.
Calibration of all three ranges must be performed during one power on period for all three
range calibration symbols to appear.
Note: The meter allows for a 1, 2 or 3 point calibration. If calibration is done for more than
one point the lowest value standard should be done first to obtain the best accuracy.
Considerations and Techniques
• Do not touch the inner surfaces of the conductivity electrodes. Touching the surface
of the platinized electodes may damage and reduce the life of the probe.
• Store the electrode in the wetting cap with the sponge moistened with pH 4.01 buffer
solution.
• Always rinse the electrode in de-ionized water between measurements to avoid cross
contamination of the sample. Double rinsing is recommended when high accuracy is
required.
• Periodically, accumulated salt deposits from the reference electrode may build up in
the storage cap, and should be rinsed away. These deposits could affect measured
values of low conductivity samples.
• When measuring low conductivity samples, extra care is recommended in rinsing the
probe to avoid contamination of the sample with electrolyte from the pH reference
electrode. This will only be a factor when measuring in the low range, and can be
further minimized by increasing the volume of the sample. (Example: Try a 200 to 500
mL sample.)
• If the 20mL sample cup is to be used, then the electrode should not be allowed to sit
in the sample for any longer than necessary, to avoid electrolyte leakage into the
sample, raising the conductivity value.
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EC500 V2.3 3/08