US1103640A

US1103640A - Thermo-electric pyrometer.

Info

Publication number: US1103640A
Application number: US71979912A
Authority: US
Inventors: Charles H Wilson
Original assignee: Individual
Current assignee: Individual
Priority date: 1912-09-11
Filing date: 1912-09-11
Publication date: 1914-07-14
Anticipated expiration: 1931-07-14

Description

CHARLES H. WILSON, 0F MOUNT VERNON, NEW YORK.

THERMO-ELECTRIC PYROMETER.

Specification of Letters Patent.

Patented July 14, 1914.

Application led September 11, 1912. Serial No. 719,799.

T0 all 'whom it may concern Beit known that I, CHARLES H. WILSON, a citizen of the United States of America, and a resident of the city of Mount Vernon, county of Westchester, and State of New York, have invented certain new and useful Improvements in Thermo-Electric Pyrometers, of which the following is a specification.

This invention relates to improvements in thermo-electric pyrometers. i

The object of my invention is to provide means for increasing the accuracy of the reading and for decreasing the cost of the device.

It has hitherto been proposed to use extension-pieces of metallic compositionsimilar or dissimilar to the elements of the thermo-couple and having approximately the same electromotive `force within limits as a means of making the thermo-couple itself short, and thereby reducing original or renewal cost, but one of the objections to that method is that the extension-pieces must be of different construction from the other elements of the thermo-couple, the most notable difference being that the elements `of the couple are ordinarily weldedv together, while the elements of the extensionpieces or leads must be insulated fromeach other throughout their length evenl at their terminals, though, of course, they are ultimately brought in series by electrical connection through the thermo-couple and through the instrument. By my invention it will generally be possible to use two ordinary thermo-couples ofthe same type and interchangeable, one being employed for use 1nA the furnace and the other as the compensator couple.

There was heretofore employed a secondary thermo-couple of the same material as the primary couple, which was of rare metal, connected in opposition thereto, but the compensator couple so used was only for the purpose of making it convenient tc employ a detachable water-cooled device to the cold end of the'primary couple, as it is not convenient to inclose the two cold junctions of the primary couple in a Water'- jacket because the leads would then have to be connected and disconnected within the water-jacket. Compensator couples con- :nected in series with the primary couple have also heretofore been employed. But when a compensator couple is connected in couple, as would occur if all were within.

one connection box, the compensator couple would have its hot and its cold junctions all at the same temperature and it would create no electromotive force and accomplish no compensation. But these devices had the disadvantage of giving inaccurate readings,

owing to their susceptibility to the fluctuation in the temperature of the cold ends of the primary couple and in the necessity of requiring means for keeping those ends at uniform and substantiallyfconstant temperature. Or, on the lother hand, such devices y had the disadvantage'of requiring compensation means composed of expensive metals, whereby the readings were to a certain eX- tent corrected.

My invention consists in arranging a secondary couple of inexpensive metal with a primary couple, by connecting the secondary couple in opposition to the primary couple, all of the junctions of said couples with each other, and the leads, being maintained at substantially uniform but not necessarily constant temperature, whereby the readings are rendered independent of the fluctuations' of the temperature of the zone including said junctions, and whereby the secondary couple is enabled to be located at any point distant from the source of heat being measured, and is not required to have a temperature relative to or the same as the cold ends of the primary couple.

The invention more specifically consists in connecting a thermo-couple of some rare and noble metals, such as, for instance, platinum and an alloy of platinum and rhodium, or of the base metals, suchy as, for

instance, iron and an'alloy-.of copper and nickel, in opposition or opposed potential (the opposite of connection in series) with another thermo-couple of base metals or their alloys, and having all the junctions in a zone of uniform temperature.

Fig. 4 shows a pyrometer embodying the invention and comprising compound primary and secondary couples connected to leads 'and a measuring instrument, and Fig. 5 is a section through a j unction-box and the connected elements of the pyrometer as practically constructed.

Similar letters of reference indicate corresponding parts in the figures4 of the drawm glhe primary couple is shown at A, a being what is generally known as the hot juncl material tion, d 'and e being what are generally known as" cold junctions. The elements ad and. ae are dissimilar in composition, and may be of noble or base metals or their alloys. The secondary or compensator couplel B has b as a junction analogous to a, while c and f are junctions analogous to al and e.

The elements be and bf are of dissimilarv material, composed of base metals or any of their alloys. Junctions@ and d may be in direct contact or in contact through some short piece of electrically conducting material. Junctions e and f are connected by ordinary copper or aluminum leads E and F to the measuring instrument at S. The primary couple A and secondary couple B when made of similar materials have the element ad of the primary couple'and the element be ofthe secondary couple of the same material and the element ae of the primary couple and the element bf of the secondary couple both of the same material, which however is dilerent from the material in ad and bc; which is .the reason for the specicationthat the thermo-couples are to be connected in opposition (the opposite of in series). When the elements of the primary cou le are oneor both of diii'erent om the elements composing the secondary couple, the elements composing the secondary'couple will be selected from such materials, as for the same change of temperature, within limits, will result in approximately the same thermo-electric effeet, or, in other words, the secondary couple and the primary couple' have approximately the samev thermoelectric force. The primary and secondary couples are then connected so that the current generated in the secondary couple tends to flow in the same direction relatlve to the direction of the current generated in the primary couple as if the elements of the secondary couple were made of the same materials as the elements of the primary couple. The junctions e, d, c and f, are arranged Within a small compass or otherwise located so as to maintain them within a zone' of approximately uniform but not necessarily constant temperature so that calibrations -may be made and readings ltaken on the assumption that all four of junctions e, d, 0 and f. The temperature of the zone may, as reckoned on any temperature scale, be between the temperatures of the junctions a and b and when this is the case and when the two elements of the primary couple A'have their direction of polarity such that the current generated,

in the primary couple flows from e -to a to d, then the current generated in the secondary' or compensator couple B will tendV to flow from c to b to f, which is in the same electrical direction, as would of course follow from the fact lthat the co-u les are' connected in opposition and have e analogous junctions a and b, one higher and one lower than the uniform temperature of their other junctions which areV all within the zone. The temperature of the zone z may be lower than that o'f either the junction a vor the junction I) and then when the current in the primary couple flows from e to a to d the current generated inthe secondary or compensator couple tends to iiow` from f to I) to c in opposition to the current generated in the primary couple as must naturally result from'the two couples con.- nected in opposition and with their a ogous junctions a and b, both heated ab 've the temperature of the zone. The effect of 'thisvcompensatorcouple is su'ch that if fthe temperatures of. junctions a and b remain constant and the temperature of the zone drops, increasing the difference in temperature between the zone and a `which results in increasing the electromotive 'force gene ated in a couple A, the current generate inthe couple B will tend to neutralize ther additional electromotive force generated in theiprimary couple and this will be accomplished either by the generation of an increased counter electromotive force in the compensator couple, when the currents generated in the primary and compensator couples vact in opposite directions, or by av reduction of the electromotive force generated in the. compensator couple when that current flows in the same direction as the current generated in the pri-mary couple.

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The result is that the readings obtained on the measuring instrument are independent of the' temperature of the zone. Thosereadings are not independent of the temperature i of the junction a within the furnace or other structure G, and it is not desired that they should be for it is desired that they actually show the temperature of the junction "a and-A temperature underground as in F ig.; 2, or

to a point within the measuring instrument as in Fig. 3.

Inasmuch as fluctuations in temperature of the junction b have an undesirable effect in disturbing the readings, I use when placing the junction I) within the measuring instrument, and for especially accurate work, some automatic device for accelerating or retarding the motion of the indicating hand as a` further compensation and wish to make clear that my invention relates to extending the junction b to the measuring instrument even tho-ugh a further compensator in the instrument is employed, although my invention does not relate to the use of such a compensator per se in the instrument as such compensators are already employed in the thermo-electric pyrometers.

The connections between the leads and the four elements of the couples within the zone 2 may be'made by soldering or any convenient quick and detachable connectors.

lVhile inFig. l I have illustrated the couples as being made up each of two wires, one wire for each element, or any other approved construction of thermo-couple, as for instance, the one shown .in Fig. 5, in which a tube replaces one of the wires, may be employed. In Fig. 5 is shown a couple of this type in which M indicates a tube of size suficient to receive the wire n, the tube being tapered at one end where it connects with and supports the wire, the junction of the tube and wire at the apex of the cone constituting the thermo-electric junction.

Inasmuch as it is frequently advantageous 'when measuring low temperatures to use several thermo-couples connected in series, all of the couples having their hot junctions in the same zone of temperature being measured and their cold junctions in a zone outside of the furnace, all of which is done for the purpose of building up the electromotive force which is directly multiplied by the n umber of couples so connected in s'eries, a plurality of couples may be used, constituting one compound primary couple analogous of the single primary couple show-n in the drawing and a plurality of couples constituting a compensator couple analogous to the single compensator couple shown in the drawing. The method of junction and arrangement of compound couples is shown in Fig. 4.

By connecting the couples in opposition I mean the reverse of connection in series. Thermo-couples are said to be connected in series when" a metal or alloy, constituting the first element* of a couple, being electropositive to the second element of the couple and connected to that second element at one end of the couple, is, at the other end of the couple, connected to an element of the second couple, to which element of the second couple it is also electropositive, the remaining element of the second couple being electro-positive to the first-mentioned element of the second couple, resulting in every alternateelement being of the same thermoelectric order of polarity. Inasmuch as the direction of the current generated in the thermo-couple depends on which end of the couple is hotter than the other end, it is evident that reversing the temperatures of the two 'will result in current flowing in the opposite direction. Inasmuch as the junctions aand band the zone .a may, any of them, be hotter or cooler than any one other, or both others, my reference to connecting the couples in opposition relates to connection in such manner than under the same conditions the element ea is electropositive to the element da when under those conditions the element fb is electro-positive to the element 0b. In other words,1f junctions a and b were both hotter or both colder than the zone the currents generated in the two couples would oppose each other.

In Fig. 5 is shown a junction-box com- .prising a base-portion L with a cover M,Y

which cover is frictionally secured detachably to the basel Through one side of the box one element n passes, and is insulated from the other element 11.2 by a collar n1. The elements pass downwardly, bein broken away in the drawing and act in t e same manner as the primary couple A shown in Fig. 1. The other couple corresponds to the couple B shown in Fig. l, and has one element r secured to the base-portion L and the other element r1 within the element 1' and passing through an insulating collar r2 and into the junction-box. The element r andI the element n2 are electrically connected by means of the base L. The element r1' is connected with a lead t which connects with the measuring instrument (not shown in Fig. 5) and the element n is connected by v of said compensator couple being dissimilar in composition to the elements of the primary couple, and having an electromotive force approximately the same as the electromotive force of the primary couple withinthe limits of temperatures occurring at thel point of connection between the primary and compensator couples and means for maintaining the junctions of the couples with each other and with their leads at substantially equal and uniform temperature, said compensator couple having its active end located beyond the influence of Vsaid means.

2. In a thermo-electric pyrometer, a pri mary thermo-couple, ordinary conducting` low resistance leads coperating therewith, a current measuring device connected therewith, a compensator couple connected in opposition to the primary couple,'the elements of said compensator couple being dissimilar `in composition to the elements of the primary couple, and having an electromotive force approximately the same as the' electromotive force of the primary couple within the limits of temperatures occurring at the pointiof -connection between the primary and secondary or compensator coup1es; said compensator couple and the primary couple being each of maintaining the junctions of the couples l with each other and with their leads at substantiall'y equal and uniform temperature,

each of said compensator couples having its active end located beyond the influence of said means.

3. A thermo-'electric pyrometer, comprising a primary couple, va secondary couple connected in opposition thereto, and means for maintaining the junctions of the couples with each other and with their leads at substantially equal and uniform temperature, said secondary couple having its active end located beyond the influence of said means.

4. A thermo-electric pyrometer, comprising a primary couple, a secondary couple connected in opposition thereto, means for maintaining the junctions of the couples with each other and with their leads at substai ially equal and uniform temperature,

the secondary couple having its lactive end located beyond the influence of said means, and means for maintaining the active junction of the secondary couple at ya constant temperature.

5. A thermo-electric pyrometer, comprising a primary couple, a secondary couple connected in opposition thereto, and a junction-boxv assembling the junctions of the couples and the leads connected therewith formaintaining the junctions at substantially equal and uniform temperature, the active end of said secondary couple being located outside said junction-box.

In testimony, that I claim the foregoing as .my invention, I have signed my name in presence of `two subscribing witnesses.

CHARLES II. WILSON.

Vitnesses:

C. M. NICHOLSON, ERNESTINE H. LrMA.