Half-Cell Pro@S - Elcometer 331 Operating Instructions Manual

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HALF-CELL PRoBES
12
HALF-CELL PROBES
(This section applies to Elcometer 331 Model BH only)
Two lypes of half-cell probe
are available for
your Covermeter
The probes can
be
easily identified
by colour:
.
Copper-Copper Sulphate (Cu-CuSOa): Yellow
.
Silver-Silver Chloride
(Ag-AgCl):
Blue
12.1
Wetting your probe
For your probe
to
function properly the ceramic sensing end (the electrode) must
be
wet
To get
a
good wet electrode,
just
place the electrode in tap water for two to three minutes; this will usually
be
sufflcient to keep the sensor going all
day Keeping the plastic end cap
on
the sensor when it is
not being
used
will also
help
to
keep
the electrode
wet
During periods
of
extended storage, place
a
small amount
of
water
in
the end cap before pushing the cap onto the probe
'12.2
Care
of
your probe and cables
The probes do not require any maintenance; they do not need recharging and are sealed
for
life
Any mud or
grit should be removed from the electrode
by
swiding the electrode back and forth
in
a
container of
warm,
soapy
water and then brushing with
a
wet
rag
The
soapy water will
not
harm or
contaminate the electrode
Always check that the
connecting cables
are
free
of
damage such as cuts and
tears
in
the sheathing
before
use
The Copper-Copper Sulphate half-cell probe is intentionally
filled
with
a
reserve
of
saturated Cuoric Sulfate solution
combined
with solid Cupric Sulfate crystals
to
ensure
a
minimum 1o-year
design
life
Under certain circumstances a very small percentage
of
this
reserve
can leach out from the ceramic sensing
tip of
the
half-cell producing crystals as shown
in
the photograph
This does not
affect the performance
of
the
cell
The crystals
should be removed
by
washing in
distilled water
12.3
Temperature
Do not allow the
probe to freeze Although freezing will
not
damage your probe,
it
will
be
impossible
to obtain reliable measurements while
in
this
state
All measurements are affected by temperature;
if
you take two readings in identical conditions, one
in the summer at
29'C (85'F)
and the other
in
the winter
at 1'C
(34"F), the half-cell potential readings will be different
Each orobe
is
tested
at 25'C to be within
+10mV of
a
standard
Calomel reference
cell
The
following values relative to
a
standard Calomel cell are used
as
the test limits during manufacture:
Lower
limit
Reference value for
Calomel
Upper limit
Copper-Copper Sulphate
(Cu-CuSO4) +50
mV
+60
mV
+70 mV
Silver-Silver Chloride
(Ag-AgCl)
-50
mV
-40
mV
-30 mV
12.4
Shelf life
Your probe does not degrade when stored
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