4 ph calibration, Ph calibration – Xylem handylab multi 12 User Manual
Page 22
Operation
handylab multi 12
22
ba75371e03
11/2009
4.2.4
pH calibration
Why calibrate?
pH electrodes age. This changes the asymmetry (zero point) and slope of the
pH electrode. As a result, an inexact measured value is displayed. Calibration
determines the current values of the asymmetry and slope of the electrode
and stores them in the measuring instrument. Thus, you should calibrate at
regular intervals.
When to calibrate?
z After connecting another electrode
z When the sensor symbol flashes:
– after the calibration interval has expired
– after a voltage interruption, e. g. after changing the batteries
AutoCal TEC
is specially matched to the SI Analytics technical buffer solutions as a fully
automatic two-point calibration. The buffer solutions are automatically rec-
ognized by the measuring instrument. Depending on the instrument setting
(see section 4.8 C
), the instrument displays the relevant buffer
nominal value or the current electrode voltage in mV. The calibration can be
terminated after the first buffer solution. This corresponds to a single-point
calibration. To do this, the instrument uses the Nernst slope (-59.2 mV/pH
at 25 °C) and determines the asymmetry of the electrode.
AutoRead
The calibration procedure automatically activates the AutoRead function.
The current AutoRead measurement can be terminated at any time (accept-
ing the current value) by pressing
Displaying the
calibration data
You can view the data of the last calibration on the display. The proceeding
is described on page 50.
Printing the
calibration
protocol
The calibration record contains the calibration data of the current calibration.
You can transmit the calibration protocol to a printer via the serial interface
(see O
Note
You can automatically print a calibration record after the calibration. To do so,
connect a printer to the interface according to section 4.7.2 before calibrating.
After a valid calibration, the record is printed.