EUTECH INSTRUMENTS ALPHA PH 500 PHORP 2-WIRE TRANSMITTER (REVISION 1), Instruction Manual, Page: 11 / 28

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4 CALIBRATION
4.1 Preparing the Transmitter for Calibration
Before starting calibration, make sure you are in the correct measurement mode.
When you switch on the transmitter, the transmitter starts up in the units last used.
For example, if you shut the transmitter off in “mV” units, the transmitter will read
“mV” units when you switch the transmitter on.
Be sure to remove the protective electrode storage bottle or rubber cap of the
electrode before calibration or measurement. If the electrode has been stored dry,
wet the electrode in tap water for 10 minutes before calibrating or taking readings to
saturate the pH electrode surface and minimize drift.
Wash your electrode in deionized water after use, and store in electrode storage
solution. If storage solution is not available, use pH 4.01 or 7.00 buffer solution.
Do not reuse buffer solutions after calibration. Contaminants in the solution can
affect the calibration, and eventually the accuracy of the measurements.
The transmitter features two internationally recognized buffer standards. Select the
buffer standard you require in the CAL mode Select from the following buffer
options:
•
First-point : pH 7.00 (USA buffer) or pH 6.86 (NIST buffer).
•
Second point: pH 4.01, 9.18, or 10.1.
NOTE: When transmitter is entered into the CAL mode, the 4/20 mA output current will
be automatically held*. ‘HOLD’ will be displayed on LCD. After Calibration and
transmitter is returned to MEAS mode, the ‘HOLD’ is automatically released.
* Please refer to page 14, section 6.4 for more details.