Delta OHM HD2205.2, Manual

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In absence of the temperature probe or sensor, the lower display shows the MTC (Manual Compen-
sation Temperature). If the correct value is not entered manually, the extent of the error committed
in pH measurement is proportional to temperature and measured liquid pH value itself.
In
MTC mode, in order to manually change the compensation temperature press F5=°C/°F once:
The indicated temperature value starts blinking. Select the desired temperature value by using the
and arrows, and confirm with ENTER. The display stops blinking, and the temperature dis-
played is used for compensation.
During manual compensation, in order to change the unit of measurement between °C and °F,
it is necessary to press the °C/°F key twice
.
pH electrode calibration
The electrode calibration is used to compensate the asymmetry potential and slope departures to
which the electrode is subject with time.
The calibration frequency depends on the accuracy desired by the user and on the effects that the
measured sample has on the electrode. Generally, we recommend daily calibration, but it is the
user's responsibility from personal experience, to establish the most appropriate frequency.
The calibration may be carried out using one or more points (up to 5): when using 1 point, the elec-
trode offset is corrected, with 2 points the offset and the gain is corrected.
The instrument has a memory of 13 buffers with relevant temperature compensation tables (ATC)
plus a “CUSTOM” buffer, not compensated for temperature. The five buffers can be selected by us-
ing the
BUFFER_1, …, BUFFER_5 menu items. Usually two for the acid, one for the neutral, and
two for the alkaline band will be selected:
@25°C
BUFR_1 (NEUTRAL)
6,860 6,865 7,000 7,413 7,648
BUFR_2 (ACID)
1,679 2,000 4,000 4,008 4,010
BUFR_3 (ALKALINE)
9,180 9,210 10,010
If electrode calibration was not carried out on the instrument, or the last calibration failed, the dis-
play blinks the
CAL message.
Calibration procedure
1. Select the buffers in the “ Measurement and pH Calibration Options ” >> “ pH Standard Solu-
tions ” menu item (please see the menu description on page 17). This operation must be per-
formed only the first time or when the normal calibration buffers are changed.
2. Insert the SICRAM pH/temperature probe or the electrode and temperature probe in the solu-
tion of the selected calibration buffer. If no temperature probe is available, use a thermometer
and enter the value manually as indicated in the paragraph “
Automatic or Manual pH Compen-
sation ”.
3. The electrode calibration mode is started by pressing CAL .
4. Select the pH input connected to the electrode being calibrated.
5. Among the three prepared buffers, the instrument automatically detects the closest to the pH
value being read, and shows the nominal value at 25°C on the right with a blinking arrow.