Extech Instruments EC170 User Manual page 8

Calibration
Calibration Preparation and Considerations
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 deionized or 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. Remember not to re‐use calibration solutions; contaminants in the
solution will affect the calibration and the accuracy.
Salinity Calibration Procedure
1. Insert the probe into deionized or distilled water for approximately 30 minutes to rinse the
probe.
2. Select the Sodium Chloride standard that is closest to the expected measurement range.
3. Fill two separate and clean sample cups with the standardizing solution to a depth of at
least 3 cm (1.2") each.
4. Switch the meter ON.
5. Rinse the probe in one of the sample cup solutions, gently stirring the probe. Rinsing could
remove contaminants that could affect calibration and cause measurement errors.
6. Dip the rinsed probe into the other sample cup solution. Tap or move the electrode in the
sample to dislodge air bubbles. Let the probe stabilize to the solution temperature.
7. Press and hold the HOLD/CAL button (approximately 2 seconds) until the salinity value and
the 'CAL' icon begin flashing on the LCD.
8. Use the arrow buttons to adjust the displayed value to match the value of the standard
solution. The Salinity reading can be adjusted ±30% from the detected value. Values
differing more than ±30% from the detected value indicates that the electrode needs to be
cleaned.
9. When the CAL icon stops flashing, press the SET button momentarily to confirm the value.
The meter will then return to the normal measurement mode.
10. Note that in cases where the Salinity reading is outside the ±30% window, the meter display
may freeze and not allow the user to return to the normal operating mode. In this case,
remove one of the batteries to switch the meter OFF and do not use the meter again until
the electrode has been cleaned or replaced.
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