Ph Calibration Procedure - Extech Instruments SDL100-NIST User Manual

System Reset
If the meter's keys become inoperable or if the display freezes the Reset button can be used to
reset the instrument.
1. Use a paper clip or similar item to momentarily press the reset button located on the lower right
side of the instrument under the snap-off compartment cover.
After pressing the Reset button, switch the instrument ON by pressing and holding the
2.
POWER key for at least 1.5 seconds. If using the power adaptor unplug the adaptor and then
plug it back in again to power the meter.

pH Calibration procedure

pH Calibration Considerations
An ideal pH Electrode generates a linear mV output of +/- 59mV per pH with 0mV at a pH of 7.00.
However, as time passes, the electrode ages and the mV output per pH is reduced. This is why
calibration is so important. The Electrode must be calibrated with the companion meter as often as
possible. In addition, the Electrode must be replaced when it has deteriorated or becomes defective.
The meter must also be well maintained and calibrated for best results.
Required Equipment for pH Calibration
1. pH Electrode
2. pH buffer solutions
pH Calibration Procedure
1. Prepare buffer solutions for 7.00 pH and either 4.00 pH or 10.00 pH. Use the 4.00 pH and 7.00
pH solutions for measurements that are expected to be on the lower side of the scale. Use the
7.00 pH and 10.00 pH solutions for measurements that are expected to be on the higher side of
the pH scale. Note that all three ranges can be calibrated for a full 3-point pH calibration if
desired
2. Connect the pH Electrode to the meter
3. Switch the meter ON by pressing and holding the power button for at least 1.5 seconds. Ensure
that the pH mode of operation is selected as described earlier in the Measurement section
4. Manually adjust the temperature compensation value (in Setup Mode) to match the buffer
solution temperature or use the supplied temperature probe for automatic temperature
compensation as discussed earlier (see the Temperature Compensation section for details)
5. Rinse the electrode with distilled water to remove residual solution
6. Immerse the pH Electrode and temperature Probe (if used) in the 7.00 pH buffer solution and
agitate the solution gently with the Electrode
7. Allow the calibration to stabilize for 15 to 30 seconds and view the reading on the meter LCD
8. Press and hold the CAL button for at least 1.5 seconds until the CAL icon appears on the
display and then release the CAL button
9. Use the arrow keys to scroll to the 7.00 pH display
10. Press the ENTER button to save the calibration data
11. Repeat steps number 5 through 10 for the 4.00 pH and 10.00 pH buffer solutions
12. Repeat the entire calibration to ensure optimal accuracy. Remember to rinse the Electrode
before placing it into a new solution
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SDL100-EU-EN V1.4 7/13