17
4.5
Calibration Procedure for Relative mV Measurements (For pH 100 Only)
Relative millivolt calibration is used in ISE
measurements, where it is common to use the lowest
concentration mV value as the base value for
measurements. All subsequent measurements will
then be based on this reference value. For Relative
mV calibration, carry out the following procedure:
1.
Press the MODE key to enter the Relative mV
mode.
2. The primary display shows the absolute mV
reading while secondary display shows the
temperature.
3.
On pressing the CAL key, the calibration mode is
activated. The ‘CAL’ indicator is displayed on the
LCD. The rest of the display remains the same.
4. With the Ml/
!
and MR/
"
keys, adjust the
displayed absolute mV value to the base value
required e.g. 350.0 mV (Figure 20).
NOTE: To exit this mode or re-enter the desired value
without confirming, DO NOT press CON key.
Press the CAL/MEAS key instead.
5. Press CON key to confirm the calibration. The
CON indicator flashes for one second and
disappears.
6.
The LCD now displays 0 mV reading. The meter
is now calibrated for Relative mV measurements.
7. On pressing the CAL/MEAS key, the meter
returns to the measurement mode. The primary
display now indicates the Relative mV readings,
bearing in mind that the selected base value is
350.0 mV.
The value displayed is calculated as follows:
Displayed Value = (Absolute mV reading) – (Relative
mV Base Value)
NOTE: For pH 100 model, you can check the Relative mV base value in the SETUP program
P2.4.
Figure 20: Relative mV calibration (For
pH 100 only)