...the
art
of
distell
‐
ing...
Freshness
Meter
User
Manual
Page
7
It
was
found
that
certain
dielectric
properties
of
the
fish
skin
and
muscle
alter
in
a
systematic
way
during
spoilage,
as
tissue
components
degrade.
These
alterations,
occurring
at
microscopic
level,
are
strongly
associated
with
the
gross
changes
in
appearance,
odour,
texture,
and
flavour
which
take
place
during
spoilage
and
which
are
normally
used
to
judge
freshness.
Hence,
determination
of
the
appropriate
dielectric
properties
gives
a
measurement
of
the
freshness
of
the
fish.
The
base
of
the
instrument
(sensing
head)
has
two
pairs
of
concentrically
arranged
electrodes.
This
sensing
head
is
applied
directly
on
to
the
skin
of
the
fish.
An
alternating
current
is
passed
through
the
fish,
between
the
outer
pairs
of
electrodes
and
the
resulting
voltage
sensed
by
the
inner
pair.
The
phase
angle
between
the
current
and
voltage
is
measured
and
converted
electronically
to
allow
digital
display
on
a
convenient
scale
in
the
range
0
‐
18.
The
phase
angle
and
hence
the
meter
reading
decreases
with
spoilage.
The
current
passed
through
the
fish
is
approximately
1
milliamp
and
so
cannot
harm
the
operator
or
affect
the
fish.
Between
the
measuring
electrodes
are
two
auxiliary
electrodes.
These
electrodes,
in
conjunction
with
one
of
the
carbon
electrodes,
sense
whether
there
is
proper
contact
with
the
fish.
The
fish
sensing
device
prevents
readings
being
taken
under
inappropriate
conditions
e.g.
in
air,
or
in
ice.
Since
the
phase
angle
depends
on
temperature
as
well
as
freshness,
the
reading
displayed
by
the
instrument
must
be
corrected
to
the
value
it
would
show
at
a
reference
temperature
of
0°C.
The
meter
is
powered
by
rechargeable
batteries
within
the
instrument.
They
have
sufficient
capacity
to
allow
a
full
working
day’s
operation.
Technical
data
This
User
Manual
does
not
cover
the
technical
side
of
the
Freshness
Meter
in
great
depth.
You
can
find
a
copy
of
our
Technical
Manual
on
the
CD
‐
ROM
that
is
supplied
with
the
meter,
or
you
can
download
a
copy
from
our
website.
This
will
help
you
explore
the
technical
aspects
of
the
Freshness
Meter’s
operation,
as
well
as
how
to
create
custom
calibrations.
