US3450619A

US3450619A - Oxygen detector

Info

Publication number: US3450619A
Application number: US552479A
Authority: US
Inventors: Louis C Kruse; Arthur P Tierney
Original assignee: Cambridge Instruments Inc
Current assignee: Leica Microsystems Inc
Priority date: 1966-05-24
Filing date: 1966-05-24
Publication date: 1969-06-17
Anticipated expiration: 1986-06-17
Also published as: CH453752A; GB1184572A

Description

June 17, 1969 KR ET AL 3,450,619

OXYGEN DETECTOR Sheet of2 xvi L c. KRUSE E A June 17, 1969 OXYGEN DETECTOR Sheet 3 012 Filed May 24, 1966 Mac/1m? luvsurons 00 (8%?! (7/ United States Patent US. Cl. 204-195 12 Claims ABSTRACT OF THE DISCLOSURE A detector for dissolved oxygen utilizing a plate with electrodes on the surface of the plate and a hydrogen saturated conductive liquid wetting the surface of the plate and the electrodes whereby said electrodes produce a potential upon the introduction of oxygen into said liquid.

This invention relates to apparatus for the detection of oxygen by producing electrical energy which is proportional to the quantity of oxygen present in a gaseous atmosphere and more specifically to novel and improved apparatus for the detection of oxygen affording exceedingly high sensitivity, stability and long life.

While oxygen detecting devices employing means for producing electric energy in response to the presence of oxygen have been known, such devices have required substantial quantities of a suitable buffer solution in which a pair of electrodes were immersed and the oxygen to be detected had to be circulated through the buffer solution. One such device is illustrated and described in the United States patent to Jessop, No. 3,022,241 granted on Feb. 20, 1962. Prior known devices also required constant replenishment of the buffer solution and substantial time for stabilization of the apparatus in order to produce accurate readings of the quantity of oxygen in the atmosphere being tested.

This invention overcomes the diificulties heretofore entailed with known devices and provides a novel and improved detector which stabilizes rapidly, utilizes very small quantities of a conductive solution and afiords exceedingly high sensitivities to the presence of oxygen in the atmosphere surrounding the detection means.

Another object of the invention resides in the provision of a novel and improved oxygen detector which is characterized by its simplicity, stability and ease of operation.

. Still another object of the invention resides in a novel and improved detecting element for oxygen detectors which responds rapidly to changes in the quantity of oxygen in the surrounding atmosphere and affords stable operation for extended periods of time.

A still further object of the invention resides in the provision of a novel and improved means for the detection of oxygen in a surrounding atmosphere which may be fabricated readily in quantities with the detectors having substantially uniform electrical characteristics without entailing tedious calibrating procedures.

A still further object of the invention resides in the provision of a novel and improved means for producing electrical energy which is directly proportional to the oxygen in an atmosphere surrounding the detecting means.

The above and other objects and advantages of the invention will become more apparent from the following description and accompanying drawings forming part of this application.

In the drawings:

FIGURE 1 is a perspective view of one embodiment of detecting apparatus in accordance with the invention.

FIGURE 2 is a cross-sectional view of FIGURE 1 taken along the line 2--2 thereof.

FIGURE 3 is a cross-sectional view of FIGURE 2 taken along the line 33 thereof.

FIGURE 4 is a diagrammatic view of one form of an electric circuit for measuring the voltage generated by the detector as a result of the presence of oxygen about the detecting means.

FIGURE 5 is an enlarged plan view of the detecting element used in the apparatus shown in FIGURES 1 through 4.

FIGURE 6 is a side elevational view of FIGURE 5 in partial section.

FIGURE 7 is a cross-sectional View of FIGURE 5 taken along the line 7-7 thereof.

FIGURE 8 is a side elevational view in partial section of a modified form of detector in accordance with the invention.

Referring now to the drawings and more specifically to FIGURES 1 through 3 which illustrate one embodiment of detecting apparatus in accordance with the invention, the numeral 10 denotes the outer housing which comprises a base portion 11 and a cover 12. The base portion 11 has an annular recess or chamber 13 containing the detecting element generally denoted by the numeral 14. The housing 10 is preferably made of a suitable insulating material, and, in the instant embodiment of the invention, may be formed of a suitable plastic material such as Lucite, polyethylene, polyvinyl chloride or the like. Since it is well-known that certain gases including oxygen will penetrate plastic materials, it is desirable that the wall portion 11 surrounding the recess 13 be made relatively thick and that the cover 12 have a thickness approximately equal to the wall portion 11. The cover 12 is secured to the base 11 by a plurality of screws 15, and an O-ring 16 is included between the cover and the top edge of the base portion 11 to seal the recess 13.

The base 11 of the housing has a pair of openings 17 and 18 for accommodation of

conductors

19 and 20. The bottom portions 17 and 1.8 are enlarged to accommodate a sealing material formed of a suitable wax 21 to seal the outer portion of the opening. The inner ends of the openings 17 and 18 are closed by a silastic resin 22, and the silastic is continued upwardly about the

wires

19 and 20 to avoid any contact between the wires and moisture which may accumulate in the annular channel 23 in the bottom of the recess 13.

The atmosphere containing oxygen to be detected is introduced into the chamber or recess 13 by an inlet port 24 and is discharged through the outlet port 25. The ports 24 and 25 are angularly spaced from the openings 17 and 18, and each port includes an enlarged threaded portion 26 and a relatively narrow portion 27. The inlet port 24 is closed by a threaded fitting 28. A tube 29 at the upper end thereof extends well into the chamber 13 and has a horizontally directed outlet port 30. The tube 29 is sealed in the opening 27 by a silastic resin and the fitting 28 is locked in place by fitting 31 and a cooperating O-ring or gasket 32, the latter being disposed within an annular recess 33 formed in the base portion 11. The port 25 is similarly arranged with a threaded bushing 28, a sealing ring 32' within the recess 33' and a sealing or locking fitting 31. The upper end of the bushing 28" includes a conduit 29' which terminates at the surface of the annular recess 23. With this arrangement, as a gaseous atmosphere containing oxygen and hydrogen is fed through the inlet port 24 and thence outwardly through the outlet port 25, some moisture will condense within the chamber 13. This condensation collects in the annular recess 23 and will be discharged through the outlet port 25.

While the voltage produced across the

lead wires

19 and 20 of the detector -14 can be detected and measured in any suitable manner, one procedure for the attainment of this end is illustrated in FIGURE 4. The detector 14 is fundamentally a current generating device, and it is desirable to utilize a load such as the resistor 34 to produce a voltage drop proportional to the current through the resistor. This voltage may then be amplified by a suitable amplifier 35 and the amplified voltage measured by an indicator 36 which may be either in an analog or digital form. It is to be understood of course that, while the resistor 34 is shown separately from the amplifier 35, the resistor may in fact constitute the input impedance of the amplifier 35.

The detecting element 14 is shown in FIGURES 5, 6, and 7. While this detector may take a variety of forms, the illustrated embodiment is of circular configuration and includes a provision for holding

wire electrodes

37 and 38. For convenience, the electrode 37 has been illustrated in a solid line while the electrode 38 is illustrated as a dotted line.

- The base 39 of the detecting element 14 is undercut as indicated at 40 to provide an extending annular portion 41 spaced from the bottom 42 of the base 39. The annular portion 41 has an inclined surface 43 containing an annular notch 44 as will be observed more clearly in FIGURES 6 and 7. An annular recess 45 is formed in the top surface of the base 39, and the bottom of the recess 45 has a shallow annular groove 46.

Referring now to FIGURE 5, it will be observed that the annular portion 41 of the base 39 is provided with pairs of spaced

grooves

47 and 48 on the right side thereof to provide a pair of

ridges

49 and 50 for attachment of one end of the

electrodes

37 and 38. The left portion of the base 39 as shown in FIGURE is provided with corresponding slots 47 and 48' to provide ridges 49' and 50' for attachment of the other ends of the

electrodes

37 and 38.

The annular portion 41 of the base 39 is provided with two additional sets of substantially

parallel slots

51 and 52 disposed generally at an angle of 90 degrees to the

slots

47, 47', 48 and 48. The slots 51 on the top side of the base 39 as shown in FIGURE 5 provide a series of spaced parallel ridges 53, while the slots 52 at the bottom side provide a similar series of spaced parallel ridges 54 with the

ridges

53 and 54 being offset to provide adequate spacing between the

electrodes

37 and 38 which are carried by the

ridges

53 and 54.

With the foregoing structure and with more specific reference to FIGURE 5, it will be observed that the electrode 37 which has one end secured to the ridge 49' is brought downwardly and engaged with the slot 44 in the first ridge 54, thence upwardly and into engagement with the bottom edge 41 of the annular portion 41 as will be observed in FIGURE 7. This process is repeated, and the end of the electrode 37 is secured to the ridge 49. The electrode 38 is interwoven with the electrode 37, it being initially secured to the ridge 50, then brought downwardly in engagement with the underside 41' of the ridge 54, and thence upwardly in engagement with the recess 44 of the first ridge 53. This procedure is continued in a similar manner, and the other end thereof is secured to the ridge 50. In this way, the two electrodes are placed in closely spaced relationship and insulated one from the other. It is evident of course that other modes of winding an element with two wire electrodes may also be utilized, it being merely necessary that the electrodes be closely spaced in order to achieve a high degree of efficiency in the detection of oxygen in the atmosphere surrounding the detecting device 14.

The two

electrodes

37 and 38 are preferably formed of dissimilar noble metals, and it has been found that two such metals which afford excellent results are gold and platinum, the latter preferably having a coating of platinum black on the outer surface thereof. The

lead wires

19 and 20 are also preferably formed of gold and platinum, and the connections 19 and 20' are made merely by twisting the leads together to form a firm connection without the utilization of any third metal which may result in the production of undesirable potential.

The base 39 of the detecting element 14 is preferably made of a material that will retain a thin layer of a conductive liquid on the surface thereof to form a conductive path between the

electrodes

37 and 38 which also lie on the surface 39 of the base 39. While any suitable material may be employed for this purpose, one material which has been found particularly effective includes an epoxy resin containing talc. The proportion of talc mixed with the resin is not critical, though it has been found that if one part of talc by weight is mixed with four parts of the resin by weight the resultant structure will retain a layer of liquid on the surface thereof. It is of course important that the surface 39 be free of any foreign matter and it is also preferable that the completed element be stored in the solution to maintain it in a moist condition. The solution utilized with the detecting element 14 should be preferably a buffered solution of the type set forth in the aforementioned United States patent.

While the apparatus is useful in a variety of applications, it is particularly useful in connection with the measurement of oxygen in a hydrogen-oxygen atmosphere since it is important that the conductive liquid on the surface of the detector 14 be maintained in a hydrogen saturated condition. One example of the utilization of a hydrogen-oxygen atmosphere for the detection and measurement of oxygen is described in the aforementioned United States patent and concerns the detection of dissolved oxygen in the water systems of modern electricity producing water systems. In this application, a portion of the water is mixed with hydrogen and an atmosphere is produced wherein the quantity of oxygen in the atmosphere bears a direct proportional relationship to the total amount of dissolved oxygen in the feed water. This hydrogen-oxygen atmosphere is then fed to the inlet port 24, fills the chamber 13 and is discharged through the outlet port 25. The oxygen in the atmosphere will dissolve into the conductive liquid on the surface of the detector 14 and produce a voltage between the electrodes proportional to the amount of oxygen entering the liquid. Furthermore, the hydrogen will maintain the liquid in a hydrogen saturated condition. In actual practice, it has been found that this detector will produce stable measurements of minute quantities of oxygen in boiler feed water, as for example, it can detect as little as one part of oxygen in one billion parts of boiler feed water.

In the case of applications wherein the quantities of dissolved oxygen in a liquid are relatively high, a structure such as that illustrated in FIGURE 8 may be utilized in order to reduce the quantity of oxygen entering the chamber 13. The structure shown in FIGURE 8 may be identical to the structure previously described and accordingly like numerals have been used to denote corresponding components of both forms of the invention.

FIGURE 8 differs from the preceding embodiment of the invention in that a plastic tube 55 pervious to oxygen and hydrogen extends through the chamber 13. In the instant form of the invention, the side wall 11 of the base 11 is provided with a pair of aligned openings through which the tube 55 extends. One side of the tube is sealed to an inlet fitting 56 while the other end of the tube is sealed to the outlet fitting 57. With this arrangement, a gas having a very high percentage of oxygen can be passed through the tube 55 and only a small proportion of the oxygen will penetrate the tube and activate the detector 14. Such a gas may also contain free hydrogen which will penetrate the tube and maintain the detector 14 in a hydrogen saturated condition. In the event the gas which is passed through the tube 55 does not contain hydrogen, hydrogen can be introduced through the inlet port 24 as previously described. Should the hydrogen be introduced into the chamber 13 through the tube 55, then of course 5 the embodiment of the invention shown in FIGURE 8 would not require the inlet and outlet ports 24 and 25 respectively.

In instances wherein it is found that appreciable quantities of moisture are deposited on the walls and bottom of the chamber 13, it is desirable to raise the detector 14 from the bottom of the chamber 13. For this purpose, a small plate of insulating material 14' may be cemented to the bottom of the chamber 13, and the detector 14 then cemented or otherwise adhered to the top surface of the element 14'. The same procedure is also preferably utilized in the embodiment of the invention shown in FIG- URE 8.

While only certain embodiments of the invention have been illustrated and described, it is apparent that alterations, modifications and changes may be made without departing from the true scope and spirit thereof as defined by the appended claims.

What is claimed is:

1. An oxygen detector for producing electric energy in response to the presence of oxygen comprising a plate of insulating material, a pair of electrodes adjoining one surface of said plate with each electrode comprising a plurality of substantially parallel conductive elements, the elements of one of said electrodes being formed of one noble metal while the elements of the other of said electrodes are formed of another noble metal, said electrode elements of different metals being arranged to place at least certain of the electrodes of one metal in closely spaced relationship with electrode elements of the other metal, and a hydrogen saturated conductive liquid Wetting the surface of said plate and said electrodes, said electrodes producing a potential therebetween upon the introduction of free oxygen into said liquid.

2. An oxygen detector according to claim 1 wherein said plate is formed of a mixture of an epoxy resin and talc.

3. An oxygen detector according to claim 1 wherein said plate is formed of approximately four parts of an epoxy resin by weight and approximately one part talc by weight.

4. An oxygen detector according to claim 1 wherein said electrodes are gold and platinum black respectively.

5. An oxygen detector according to claim 1 wherein said plate is provided with spaced ridges on at least certain portions of the periphery thereof and the elements of said electrodes are in the form of wires engaging said ridges and lying on the surface of said plate, said wires being spaced one from the others throughout their extent.

6. An oxygen detector according to claim 5 wherein the elements of each electrode constitute a continuous wire engaging opposing ridges to form effectively a plurality of spaced transverse elements with the elements of one electrode being in closely spaced relationship to the elements of the other electrode and wherein said wires are gold and platinum with the latter coated with platinum black.

7. An oxygen detector for producing electric energy in response to the presence of oxygen comprising a sealed hollow housing including fiuid inlet and outlet openings, a detector within said housing, said detector having a plate of insulating material, a pair of electrodes adjoining one surface of said plate with each electrode comprising a plurality of substantially parallel conductive elements, the elements of one of said electrodes being formed of one noble metal while the elements of the other of said electrodes are formed of another noble metal, said electrode elements of different metals being arranged to place at least some of the electode elements of one metal in closely spaced relationship with electrode elements of the other metal, and a hydrogen saturated conductive liquid wetting the surface of said plate and said electrodes, electrical conductors extending through said housing and connected to said electrodes, and indicating means connected to said conductors.

8. An oxygen detector according to claim 7 wherein said plate is formed of a mixture of an epoxy resin and talc.

9. An oxygen detector according to claim 7 wherein said plate is provided with spaced ridges on at least certain portions of the periphery thereof and the elements of said electrodes are in the form of wires engaging said ridges and lying on the surface of said plate, said wires being spaced one from the others throughout their extent.

10. An oxygen detector according to claim 7 wherein said plate is provided with spaced ridges, the elements of said electrodes each constitute a continuous wire successively engaging opposing ridges to form eifectively a plurality of spaced transverse elements with the elements of one electrode being in closely spaced relationship to the elements of the other electrode and wherein said wires are gold and platinum with the latter coated with platinum black.

11. An oxygen detector according to claim 7 wherein said outlet opening constitutes a drain for liquids condensing within said housing.

12. An oxygen detector according to claim 7 wherein said inlet and outlet openings are connected within said housing by an oxygen permeable tube.

References Cited UNITED STATES PATENTS 3,022,241 2/1962 Jessop 204- 3,196,100 7/1965 Digby 204-195 3,223,609 12/1965 Reeds 204-195 FOREIGN PATENTS 941,436 ll/ 1963 Great Britain.

JOHN H. MACK, Primary Examiner.

T. TUNG, Assistant Examiner.

US. Cl. X.R. 204242, 280