13
d.
Interpreting
Data
i.
Metal
Loss
The
MS2701E
transmitter
measures
the
Metal
Loss
of
an
ER
probe
and
converts
that
value
to
a
digital
16
‐
bit
RS
‐
485
Modbus
output.
This
output
is
directly
proportional
to
the
cumulative
Metal
Loss
of
the
ER
probe
at
any
given
time.
The
overall
span
of
the
output
is
proportional
to
the
life
of
the
probe
in
use,
so
for
DCS/PLC
programming
the
RS
‐
485
Modbus
output
can
be
scaled
as
follows:
0
=
0
mils
(0%
Metal
Loss)
65535
=
Probe
Life
in
mils
(100%
Metal
Loss)
The
Probe
Life
can
be
found
in
Table
1
and
is
also
listed
on
the
Metal
Samples
probe
tag
(as
the
“Multiplier”.)
Figure
7.
Metal
Samples
Probe
Tag
Figure
8
illustrates
the
relationship
between
the
digital
output
and
Metal
Loss.
In
this
example
a
probe
with
a
10
‐
mil
life
is
assumed.
However,
the
X
axis
could
be
changed
to
represent
any
Probe
Life.
Figure
8.
Output
Relationship
As
seen
here,
the
transmitter
output
begins
at
0
for
a
new
probe
(zero
Metal
Loss)
and
increases
as
the
probe
element
corrodes,
eventually
reaching
a
maximum
of
65535
when
the
probe
sensing
element
has
been
completely
consumed
by
corrosion
(in
this
case,
10
mils
of
Metal
Loss.)
At
this
time
the
probe
has
reached
its
end
‐
of
‐
life
and
must
be
replaced.
0
16384
32768
49151
65535
0.0
2.5
5.0
7.5
10.0
RS
‐
485
Modbus
Output
Metal
Loss
(mils)
New
Probe
Probe
Consumed