Aquameter
™
Series Instruction Manual
10401-00188 Rev M
13.4. Calibrating pH
pH electrodes should be calibrated fully at least once a week to ensure optimum accuracy.
Full calibration involves calibrating at pH 7.00 first, then at pH 4.01. Although the
Aquaprobe allows only two point pH calibration, the pH electrodes are extremely linear and
once calibrated, will read accurately over the full range of 0 – 14.
On Aquaprobe Models AP-100, AP-400, AP-500 or AP-600 you must have a pH electrode
fitted and the Aquameter must be set to read pH or pHmV. If your Aquameter is set to read
ORP, access to pH calibration will be barred.
Due to the way in which pH calibration works,
the Probe must be calibrated at pH7.00
before calibrating at pH 4.01
. Never calibrate at pH 4.01 before first calibrating at pH7.00.
For best results, calibrate as close to 25
°
C as possible. The probe will compensate for
temperature variation in the calibration buffer and pH electrode during calibration.
To calibrate the pH electrode follow these steps:
1. Fill a 300mL calibration bottle with fresh pH 7.00 solution or RapidCal, remove the
storage cap from the pH electrode, wash the Probe in distilled water, then drop the
Probe in all the way. The Sleeve End Cap should not be fitted.
2. Switch the Aquameter on and wait until the temperature and pH measurements are
completely stable.
3. Ensure the temperature of the solution is between 5ºC and 40ºC (41ºF - 104ºF).
4. Press the
MENU
key then select
Calibration.
The following screen will be displayed.
Calibration
RapidCal
DO 100%
Full Cal
5. Select
Full Cal.
The screen will change to:
Calibration
>pH/ORP
DO/EC
Turb
6. Select
pH/ORP
. The screen will change to:
Calibration
pH7.00?[01/Jan/09]
pH4.01?[01/Jan/09]
ORP? [01/Jan/09]
The dates shown to the right of the screen are the dates of the last successful calibration. If
no ORP electrode has ever been fitted, the ORP date will be dashed out.
© 2011 Aquaread Ltd.
www.aquaread.co.uk
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