31
30
When the batteries are inserted and no power adapter is connected,
the meter can recognize different batteries charge levels.
1.
Fully charged batteries
. The backlight and printer can be
enabled.
2.
Weakening batteries
. "LOBAT" symbol blinks on LCD. The
backlight and printer are automatically disabled and it is not
possible to enable them until new batteries are inserted or an
external power adapter is connected.
3.
Weak batteries
. "LOBAT" symbol stays still on lower LCD.
Backlight and printer are disabled and meter can work for about
20 hours. If in Timed logging mode with the power down
function enabled this time can be longer.
4.
Dead batteries
. LCD shuts off. The instrument stops working to
avoid any erroneous readings.
Note:
It is not possible to enable backlight and printer when the
instrument is in a low battery condition. If the user attempts
to enable these functions without re-
placing the batteries or connecting
the external power adapter, the meter
will show "bAtt" on LCD.
Battery replacement must only take place in a non hazardous area,
by using 1.5V alkaline AA type batteries.
In order to replace run down batteries,
simply remove the two screws on the rear
cover of the instrument and replace the
four 1.5V AA batteries, while paying at-
tention to the correct polarity.
A 12 Vdc power adapter can also be used
to power the unit.
Note:
The instrument uses the following configuration.
It is recommended to purchase the Hanna
HI 710005
or
HI 710006
voltage adapters that use the proper polarity configuration.
However,
HI 98230
and
HI 98240
can also be used with other
adapters. In this case, remember to check the correct polarity of your
adapter before connecting it to the meter.
+
-
BATTERY REPLACEMENT
TEMPERATURE-RESISTANCE CORRELATION FOR
HANNA pH SENSITIVE GLASS
The resistance of glass electrodes partially depends on the temperature.
The lower the temperature, the higher the resistance. It takes longer time
for the reading to stabilize if the resistance is higher. In addition, the
response time will suffer to a greater degree at temperatures below 10°C.
Since the resistance of the pH electrode is in the range of 200 Mohm,
the current across the membrane is in the pico-Ampere range. Large
currents can disturb the calibration of the electrode for many hours.
For these reasons
high humidity environments, short circuits and
static discharges
are detrimental to a stable pH reading.
The pH electrode's life also depends on the temperature. If constantly
used at high temperatures, the electrode life is drastically reduced.
Typical Electrode Life
Ambient Temperature
1- 3 years
90 °C
Less than 4 months
120°C
Less than 1 month
High concentrations of sodium ions interfere with readings in alkaline
solutions; the pH at which the interference starts to be significant
depends upon the composition of the glass. This interference is the
alkaline error and causes the pH to be underestimated. Hanna's
glass formulations have the indicated characteristics.
-20 -20
-10
0 +10+20 +30+40 +50+60+70 +80+90
° C
-10
-10
Ω
-10
-10
-10
-10
Ω
2x10
9
1x10
9
2x10
8
1x10
8
2x10
7
1x10
7
-20 -10 0
+
10
+
20
+
30
+
40
+
50
+
60
+
70
+
80
+
90
°C
Alkaline Error
1.0 Mol L
-1
Na
+
0.1 Mol L
-1
Na
+
Sodium Ion Correction for the Glass at 20-25°C
Concentration
pH
Error
13.00
13.50
14.00
12.50
13.00
13.50
14.00
0.10
0.14
0.20
0.10
0.18
0.29
0.40
