Operational Guide; Calibration - Hanna Instruments BL120 Instruction Manual

8. OPERATIONAL GUIDE

8.1. CALIBRATION

pH Calibration
The pH electrode can be calibrated on the controller using an automatic, two-point calibration. The electrode should be
calibrated:
• Before in-line or flow cell installation
• Whenever the pH electrode is replaced
• When higher accuracy is required
• After periodic maintenance
Always use fresh calibration buffers and perform recommended electrode maintenance prior to calibration.
Note: It is recommended to choose calibration buffer solutions that bracket the pH sample.
Preparation
Pour small quantities of the buffer solutions into clean beakers. If possible, use plastic beakers to minimize any EMC
interferences. For accurate calibration and to minimize cross-contamination, use two beakers for each buffer solution; one for
rinsing the electrode and one for calibration.
If measuring in the acidic range, use 4.01 pH as the first buffer and 7.01 pH as the second buffer.
If measuring in the alkaline range, use 7.01 pH as the first buffer and 10.01 pH as the second buffer.
A minimum of two-point calibration is required.
Press MENU to enter calibration mode. Select pH options by pressing  and press CAL. 4.01 pH value is displayed
blinking.
Remove the electrode protective cap and place the probe into the first buffer solution.
If the first buffer is 4.01pH, "Recognized" is displayed followed by "Stable". Press CFM to accept the first calibration point.
Place the probe into the second calibration buffer (either pH 7.01 or pH 10.01).
7.01 pH value starts blinking automatically. If the second buffer is 7.01 pH, "Recognized" is displayed followed by "Stable".
Press CFM to end calibration.
The "pH Calibration Complete" screen will appear briefly followed by the Menu screen. Press MENU to return to measurement mode.
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