Delta HD2105.1, Operating Manual

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HD2105
- 16 -
V2.3
A
UTOMATIC OR MANUAL
pH
COMPENSATION
In a correct measurement of pH, the results need to be expressed together with the temperature
value at which the reading is performed.
The electrode slope varies according to the temperature in a known mode according to Nernst law:
e.g., a 1pH variation, that at 25°C means 59.16mV, at 100°C means 74.04mV.
6pH 7pH
pH
8pH
74.04mV
-74.04mV
59.16mV
-59.16mV
54.20mV
-54.20mV
0mV
mV
T=100°C, 74.04mV/pH
T=25°C, 59.16mV/pH
T=0°C, 54.20mV/pH
When a temperature probe is present, the instrument automatically applies the ATC automatic tem-
perature compensation function. To disable it, the temperature probe must be disconnected.
If the temperature probe is not present, and the correct value is not entered manually, the extent of
the error committed in pH measurement is proportional to temperature and pH value itself.
In absence of the temperature probe, the lower display shows the manually set compensation tem-
perature (default=25°C).
To point this condition out, the °C or °F symbol blinks intermittently near the temperature value.
Moreover, on the main display an “m” (
m anual) is turned on near the battery symbol (if present).
On the print-outs, the MT indication is printed. Instead, if the probe is present, the AT symbol is
printed.
To manually change the compensation temperature press °C/°F once: the indicated temperature
value starts blinking. By using the arrows select the desired temperature value
and confirm with
ENTER. The display stops blinking, and that temperature is used for compensation.
To change the unit of measurement between °C and °F, it is necessary to press twice
the °C/°F key.