HD2105
- 17 -
V2.3
pH
ELECTRODE CALIBRATION
The electrode calibration is used to compensate the zero potential and slope deviations to which the
electrode is subject with time.
The calibration frequency depends on the accuracy desired by the user and by the effects that the
measured sample have 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 1, 2 or 3 points. When using 1 point, the electrode offset is
corrected, with 2 points the offset and the gain is corrected; finally, in case a three points calibration
is carried out two offsets and two slopes are calculated,
the second point is the one in which the
zero is performed
.
The instrument has a memory of 13 buffers with relevant temperature compensation tables (ATC)
plus an “User” buffer, not compensated. The three buffers can be selected by using the
BUFR_1,
BUFR_2, BUFR_3
menu items. Usually one for the acid, one for the neutral, and one for the alka-
line 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
The buffers in bold are predefined in the factory, these are the “DeltaOHM” ones.
If electrode calibration was not carried out on the instrument, or the batteries have been
changed or the last calibration failed, the display blinks the CAL message.
Calibration procedure
1
) Insert the temperature probe and the electrode in the solution of a calibration buffer. If no tem-
perature probe is available, use another thermometer and enter the value manually as indicated in
the paragraph “
Automatic or manual pH compensation
”.
2
) The electrode calibration mode is started by pressing CAL.
3)
Among the three prepared buffers, the instrument automatically detects the closest to the pH
value being read and flags it up on the lower display.
If the buffer is not detected the first buffer BUFR_1 is proposed.
4)
At this point the CAL symbol is not blinking on the display and the following is shown from the
upper side downward:
a) the chosen buffer nominal value at 25°C (scrolling indication)
b) the pH measurement value with the current calibration
c) the temperature compensated buffer value
The detected and temperature compensated buffer value, shown in the lower line, can be modi-
fied using the arrows.
Summary of Contents for HD2105.1
Page 4: ...HD2105 4 V2 3 Temperature pH meter HD2105 1 ...
Page 6: ...HD2105 6 V2 3 Temperature pH meter HD2105 2 ...
Page 45: ...HD2105 45 V2 3 NOTES ...
Page 46: ...HD2105 46 V2 3 NOTES ...
Page 47: ......
