Note: Descriptions are shown in the official language in which they were submitted.
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SAFE FAILURE ION SELECTIVE COHBINATION ELECTRODE
Field of the Invention
This invention relates to ion selective combination
electrodes, and more particularly, to such devices which can
detect and signal their own breakdown.
Backqround of the Invention
General purpose pH combination electrodes that operate
over the full pH range and provide an output of about minus 60
millivolts (mV) per unit of pH, output at pH 7.0 being zero mV are
known. It is known also to shift the zero mV point, as to pH 4.0
or 10.0, to avoid automatic temperature compensating metering
circuits, by varying internal solution formulation.
Summarv of the Invention
It has been discovered that an ion selective combination
electrode in which zero mV output corresponds to ion
concentrations, such as pH, outside a desired range makes it
possible to detect an electrode's internal breakdown.
According to one aspect of the invention there is
provided an ion selective combination electrode system for
monitoring ion concentration of a test solution for which there is
an associated predetermined safe ion concentration range
comprising
an ion selective electrode, said electrode including a
vessel,
an inner solution in said vessel,
a first element in said inner solution, and
a first electrical line for making an external electrical
connection to said fir~t element,
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a reference electrode including a second element and a second
electrical line for making an external electrical connection to
said second element,
said ion selective electrode and said reference electrode
being in an electrode subsystem providing an electrical output
that varies as a function of ion concentration of said test
solution,
said electrical output having a predetermined safe electrical
output range associated with said predetermined safe ion
concentration range,
said electrical output being outside said predetermined safe
electrical output range when said electrode subsystem is
malfunctioning, and
a control unit electrically connected to said first and
second lines to receive said electrical output,
said un$t being constructed to provide a warning signal if
said electrical output is outside said predetermined safe
electrical output range,
wherein said electrode subsystem has a predetermined safe
electrical output range that is a voltage range that does not
include zero volt, and said electrical output is zero volt when
said electrode subsystem malfunctions, and
wherein said inner solution is selected to provide said
voltage range that does not include zero volt.
According to another aspect of the invention there is
provided an ion selective combination electrode system for
monitoring ion concentration of a test solution for which there is
an associated predetermined safe ion concentration range
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.
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comprising
an ion selective electrode, said electrode including a
vessel,
an inner solution in said vessel,
a fir~t element in said inner solution, and
a first electrical line for making an external electrical
connection to said first element,
a reference electrode including a second element and a second
electrical line for making an external electrical connection to
said second element,
said ion selective electrode and said reference electrode
being in an electrode subsystem providing an electrical output
that varies as a function of ion concentration of said test
solution,
said electrical output having a predetermined safe electrical
output range associated with said predetermined safe ion
concentration range,
said electrical output being outside said predetermined safe
electrical output range when said electrode subsystem is
malfunctioning, and
a control unit electrically connected to said first and
second lines to receive said electrical output,
~aid unit being constructed to provide a warning signal if
said electrical output is outæide said predetermined safe
electrical output range,
wherein said system monitors pH, and
wherein said predetermined safe ion concentration range
includes a pH value of 7.0, and said inner solution has a pH that
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is outside of said predetermined ~afe ion concentration range.
According to another aspect of the invention there is
provided an ion selective combination electrode system for
monitoring ion concentration of a test solution for which there is
an associated predetermined safe pH range that includes a pH of 7
compri~ing
an ion selective electrode, said electrode including a
ve sse 1 ,
an inner solution in said vessel that has a pH outside of
said predetermined safe pH range;
a first element in said inner solution, and
a first electrical line for making an external electrical
connection to said first element,
a reference electrode including a second element and a second
electrical line for making an external electrical connection to
said second element,
said ion selective electrode and said reference electrode
being in an electrode subsystem providing an output voltage that
varies as a function of pH of said test solution,
said output voltage having a predetermined safe output
voltage range associated with said predetermined safe pH range,
said predetermined safe output voltage range not including zero
volt,
said output voltage being zero when said vessel ruptures, and
a control unit electrically connected to said first and
second lines to receive said output voltage,
said unit being constructed to provide a warning signal if
said output voltage is outside said predetermined safe output
ld 2 0 1 9 7 2 8 74424-36
voltage range.
Preferred ~bodiment
The preferred embodiment is shown in the attached
drawing, the structure and operation of which iB then described.
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Drawing
In the drawing is shown a diagrammatic view of said
preferred embodiment.
Structure
The preferred embodiment is indicated generally at 10
in the drawing.
The ion selective combination electrode 10 has as two
functional parts an ion selective electrode indicated generally
at 12 and a reference electrode indicated generally at 14.
Ion selective electrode 12 has a glass stem 16 in
communication with ion selective glass bulb 18. Within the vessel
defined by stem 16 and bulb 18 is solution 20, in which hang
silver wire 22 with dependent therefrom silver chloride billet 24.
Inner solution 20 is a pH 5.0 solution prepared by adding
Potassium Acide Phthalate (Merck, AR Primary StandARd), 0.05 mols
phthalate, to 1.8 mols of potassium chloride, the whole made up to
a one liter quantity with deionized water, and adjusted to its
final pH with NaOH. Seal 26 provides a seal around tubular portion
16 and wire 22.
Bushing 28, which has liquid junction 30 extending
therethrough, is an annulus which positions electrode 12 within
electrode 14. The latter contains, above bushing 28, a standard
prior art reference electrolyte solution 32. Silver wire 34
extends into solution 32, and has dependent from it silver
chloride billet 36. Seal 38, which is annular, seals wire 34 and
both electrodes therearound.
Container 40 is shown with, within it, a solution 42
the pH of which is being monitored.
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Wires 22 and 34 are connected with amplifier 44, which
provides a voltage output reflecting the input from the two
wires. The unit indicated diagrammatically and generally at 46
has control and alarm circuits and provides a warning signal
if voltage goes to zero; the unit 46 is programmed so that
predetermined desired voltages are in the pH range of 6.5 to 8.2,
while zero voltage is at pH 5.5.
Outer wall 48 provides both the wall for reference
electrode 14 and a zone 50 whereat solution being tested can be
in contact with bulb 18 and junction 30, for sealed electrical
contact therethrough (through holes not shown).
The following chart compares the preferred embodiment
and prior art above referred to:
pH of a solution 4.0 5.06.0 7.0 8.0 9.0
being tested
Preferred Example ~ >
safety range (6 5) (8 2)
Preferred Example <~ .
low pH alarm range . . -~>
Preferred Example
high pH alarm range .
Prior Art electrode 180 120 60 : 0 -60 : -120
mV output l
PriGr Art electrode : x
failure point (pH 7.0)
Preferred Example 90 30 0 -30 : -90 -150 : -210
electrode mV output ¦ .
Preferred Example x :
electrode failure (pH 5.5)
Operation
In normal use, with the combination electrode 10 in the
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_ 69204-185
test liquid 42, pH is within the safe range set into unit 46,
and is therein monitored. If tube 16 ruptures, voltage goes to
zero, which in the invention is outside the safe or predetermined
operating range, and a signal circuit in unit 46 gives its signal.
The signal is also given at other voltages outside the
predeterminedly desired range.
Other embodiments within the following claims will
appear to those skilled in the art.
