Extech Instruments EC100 User Manual page 7

Calibration
Calibration Preparation and Considerations
CONDUCTIVITY Calibration Procedure
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The user must first determine:
1. The best calibration schedule for the application at hand.
2. What calibration standard to use.
Calibration Schedule

Calibration is necessary and should be performed regularly.

If measuring in the mid-ranges calibrate the meter at least once per month and soak the probe
for 15 minutes before each use.

If measuring in extreme temperature environments, or at the low end of the measurement
range, calibrate the meter at least once per week.
Selecting a Calibration Standard
For best results select a calibration standard closest to the expected sample value. Alternatively,
use a calibration solution value that is approximately 2/3 of the expected full scale measurement
range. For example, in the 1999µS range, use the 1413µS solution standard. Remember not to
re-use calibration solutions; contaminants in the solution will affect the calibration and the
accuracy.
1. Allow the probe to soak in de-ionized or distilled water for 30 minutes.
2. Select an appropriate conductivity calibration standard as discussed in previous section.
3. Pour the calibration solution into two separate, clean containers to a height of 3cm.
4. Power the meter and select the Conductivity mode using the
5. Rinse the probe in one of the calibration solution containers; gently stirring the probe.
6. Dip the probe into the second calibration solution container. Tap the probe on the bottom of the
container to remove air bubbles. Allow the probe to stabilize to the solution temperature (15
minutes is typical).
7. Press and hold the HLD/CAL button for at least 2 seconds. The conductivity value and the
'CAL' icon on the display will flash.
8. Press the and the HLD/CAL buttons simultaneously to adjust the displayed conductivity
value so that it matches the standard solution value (normalized to 25°C). The conductivity
reading can only be adjusted to ±30% of the detected value. If detected value (displayed value)
differs from the calibration standard by more than ±30%, the probe may need cleaning or the
meter may require replacing.
For example: The calibration standard is 10µS and the detected value is 19µS. The adjustable
range is ±5.7µS (19*30%). In this example the values differ over the 30% limit.
9. When the CAL icon stops flashing, press the SET button momentarily to confirm the value. The
meter will then return to the Conductivity measurement mode. If the CAL icon continues
flashing, verify that the calibration solutions are fresh and stable. Also re-check that the value
selected in step 8 is correct.
10. Repeat the procedure above for other ranges as required.
Note: When switching from measurement mode to calibration mode, the meter will display the
factory default calibration value. This is normal and does not affect the user calibration.
Note: To exit the calibration mode without confirming the calibration, press and hold the SET
button in Step 9 for at least 2 seconds. This will abort the calibration and revert to the previous
calibration values.
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button if necessary.
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