CA2152880A1 - Fluid gauging apparatus using magnetostriction and a stick gauge - Google Patents

Abstract

Apparatus for detecting fluid level in a container, comprises a housing adapted to be disposed in the container; a float with an associated magnetic element, the float position corresponding to fluid level in the container; a magnetostrictive sensor disposed inside the housing; and a stick gauge disposed inside the housing; the magnetostrictive sensor and the stick gauge each being operable to determine the float position.

Description

215 2~
Title: FLUID GAUG~NG ~PPARATUS USING
~ ~S~n~CTION AN~ A S~ICK GAUG~

Yn~OuND 0~ SF~ V~n ~ 10~
This application i8 a continuatlon-~n-part of ~o p~ ing application Seria~ No. 08l069,Z63 for ~.;T~i~ c---gin~ Apparatus With Remote Sensor Intel,~Lion~ ~iled on ~ay 28, 1993.
The invention relates generally to ~ar~L~s and methods for fluid gauging, and ~ore par~ctll~rly to apparatu~ and method6 for detecting fluid levels using ~agnetoctr$ctive S~ 6 and -- I
~tick ~d~
~any types of liguid quantity and level Fen~La are known, including capacitive senDor6, resi6tive enC~,D, acoustic n~-60~
and ~o forth. Passive ensor~ gensrally ~y~Le on the basi~ of a sensor element that ~Y~hits a parameter, e.g. c~r~citance, that var~es with the liquid level. Active ~ensor~ 5uch a~
acoustic ~ensor~ ~e~a-e on the ba~is of pro~ nq a signal, e.g.
an acoustic pulse, that can be used to detect ths liquid level by parametric analysi~ ~uch as echo ranging.
Such-syste~s further include an ele~ nic circuit that detect~ the p~ra~metric value of intere~,t and cGn~e~Ls that value to a signal that cu~r~onds to the liquid level.
A com~on application for BUCh liquid level sensor~ is for fuel level and quantity detect1on in a$rcraft fuel tanks.
Ho~ l, due to the volatile nature of ~uel, it i5 de~irable to ini ize the ~ ion of electrical energy to the ~en~ors ~hich ~ay be ~i~pos6~ in the fuel. It i6 further desirable to ini ize the al,r t of electri~al ~"~4~ stored in the ~~L~ or used by the f ~ tlDO, ~ .
A known approach for mini~izing the coupling of electrical energy into a fuel tank is described in U.S. Pat. No. 4,9~3,729, icsued to Spillman et al., and owned in _ 1 by the assignee of the present invention. In this systes, optical er.er~ is coupled to the ~.su~ via optic fibers. Thi~ optical ~_L~ i6 then co,-~lLed to electrical ~eL~ for energizing the s~ oLD.

2 21s2~0 The sen~s detect the liquid level and then transmit another optical si~a 1 back to a detector ~ia the optic fiber~. The detector then c~ D the ~ A optical ~ l into an ~t~uL
that co~ c to liquid leYel in t~e t~nk.
For aircraft a~pliç~tion_, on board re~A;n~ often need to be verified by ~v~-d creY8, either during ~outine turn a~ uu~
or to confiru an error ~-'in~. The optic41 ~i~er link to the internal sen~or in the above ~y6tem ~ .L~ as a practical ~atter inte~ogation of the e~ by ~ro~ ~ cre~s, other than via the ~ame optic fiber link ~hich may in fact be the cause of a fault rea~g A commonly u~ed fuel level sen~or in commercial aircraft particularly is a drip~tick ~en~or, whioh i8 used as a ~ach~r fuel gauging apparatu~ to the on-~oard el~_Llonic fuel ~evel sensors. Fox exa~ple, drip~tick veri~ication ~ay be n~e~ when a refueling truck gauge di~agrees with the aircraft fuel gauge, if the on-board fuel ~uge~ appear to be inaccura~e or ~ yeiative, or simply by ~e~u~aL of the ~light crew, _mong other Possible rea~ c.
The dripstick includes a linear body that extend~ vertically into the fuel tanks. Often there is a plurality of auc~
dripsticks in each wing of the aircraft. A ~gnetic float is di~posed on the dripstick body like a collar that floats at the fuel ~urface. The dripstic~ is read by the ~,u~.d crew by manually ~ithdra~ing the dripetick from the wing until a magnetic tip at the upper end of the sensor body engaqes the float. The operator can feel the resistance of ~he tip again~t the ~agnetic float and stop pulling on the dripctiok. The dripstick body includes a serie~ of marking~ which vi~ually in~ te to tne operator the fuel level based on ho~ far the dripstick was withdraYn from tbe tank. ~1~bG~gL dripstick designs may vary s~ le~l.at, the basic operation of m~ o5R and visual interrogation i~ the same for the yLu~-d crew.
Various pro~le~ are associated Yith using t~e o~ ional dripstick~, especially the time i~volved for ~he ~r~d cre~ to 3 215288~

wal~ arDund to ~ll the ~en60r~ and ~ n~ y/Vi F~ y dete~ jnD
the re~ing~. The - a~ic cli~bs a ladder or uses a lifting device to gain cloee P.Co~ to the underside of the ving, vlth~l J~ the dripstick untll the r~ detected, ~e'~l~S
the r~ and then replaces the dripstick into the tan~.
Dripstick de6ign i6 further complicated ~y the need for uini~al fuel le~k~. T~i5 entire ~ r.Fs u~t be repeated for eàch ~ - , w~ich adds sub~tantially to the ~u~ o~ Lion and turnaround ti~e ror a$rcraft flight r~
1~ Comuercial air carriers hav~ long identified the need for a drip~tiCk-like h3~r ~yste~, but one that i~ easier to u~e.
A system that can be int~,~oqa~ed ~rom the ~l~.d would eli~inate the need ~or lifting equip~ent and provide ea~ier re~ing of difficult access dripsticks. Overall ~ed~ion in refueling and fuel verification delay6 could then be realized.
Al~hough alternative fuel gauging sy~te~ are thus desirable, it i8 expected that both cn~Prcial and military aircraft customers will vant to reta~n the ~n~l dripstick design due to its fa~iliarity and si~ple design. Thi~ use of ~d~n~Ant E;ysteme present~ a pro~lem ~ec-~se there is not an unlimited ~pace available to simply add on additional ~en60 system~, nor can fuel tanks ~e modified ~ithout s~b~tantial downtime and cost.
~he o~jectives exist, ~herefore, for siDple and r~liAh]~
apparatus and ~ethods tD interrogate liguid gauging ~en~or~ ~ro~
a remote, preferably g~uund level, location withDut coupling electrical energy into a volatile contaiher. Such an arra~, - t should al~o be co~patible vith cu~e,.L dripstick E;ensOr configurations if de~ired for a particular application.

3 0 sU~aUy OF 'r~TF ~ Oal To the ~r: liE-- ~ of the fo~eg~ing ob~ective~, the invention conte~plates in one e~P~ t ~pparatu~ for detecting fluid level in a container, 5uch appar~tu~ incl~Aing a hou~ing adapted to be ~ispose~ in the container; ~ float with ~n 4 21~2~80 as~ociated magn-tic el.- ~ t, the float po~ition co,.~r~in~ to fluid level in t~e container; a ~agneto~trict$~e ~_.~v~
inside the housi~g; and a stick gauge Ai~p~æ in6ide the holl~ i ng; the magneto6trict~ve ~enso~ and the ~tick gauge each being op~rable to det~ e the fl~at po6ition. The in~ention further contemplate6 the method6 of ~lPte ting fluid level a~
~ied in the use of ~uCh ayy~atus.
The~e and other aspects and advantage~ of the ~ t invention ~ill be readily understood and ~yy.e~iated by tho~e skilled in the ~rt from the following de'ta$1ed description Or the preferred em~QA; LB with the be~t mode cont~ ,lated for practicing the invention in vie~ of the ~ _ n~ing dra~ings.

B~IEF ~.4~K~ ON 0~ THE ~WINGS
Fig. lA is a si~plified r~ sel~ation of a liguid quantity gauging ~ystem according to the invention, ~uch ~yste~ being ~ ally ~ho~n in an exe~plary ~anher for u5e with aircraft ~uel gauging;
Fig. lB i~ an enlarged simplified view of an optics arr~n~ t for the exemplary use depicted in Fig. lA;
Fig. 2 is a ~ystem functional block diagram for a sen60r interrogation Ey~te~ and method that uses a renote hand held interrogation unit and el~ct~u..ic Cu~l~r~l circ~it according to a preferred ~ of the invention;
Fig. 3 is a ~implified flo~ chart for opera~isnal functions of the system illu~trated in Fig. 2;
Fig. 4 is a partial cross-6ectional vie~ of a dripstick sensor suita~le for use with the present invention;
Fig. 5 is a schematic diagram of an e..~ c~ cion and control circuit suitable for use ~ith the ~E--~ in~ention, ~nd Fig. 5A is a e~~ .tic of an alternative and simpler circuit suitahle for use in many applications;
~ ig. 6 i~ a schematic diagram o~ s~n~ interface and e~o~r circuit6 ~uitable for use with the invention, and Fig.
6A show6 another suitable er~fl~ L for an ~ _ circuit;

21~2~80 Fig. 7 ls a timing diagra~ shoving ~ entative p~ 3~
c~d ffl an ~o~ circuit 6u$ta`ole for use ~ith the present invention;
Fig. 8 is a 6~h - etic diagra~ of an LED/Driver circuit for the pre~ent invention;
Figs. 9A and 9B ill~ a~e in 6chematic for~ another e~bodi~ent of t~e in~ention tbat il-~u ~ur~es a ~aqnetostrictt`ve sensor and stick gauge;
Fig. 10 i~ a detailed illu~L~a~ion in ~e~e~Live of the . ~iment of Fig~. 9A and 9~;
Fig6. llA-llC $11ustrate one e~bodiment of a self-cont~ine~
dripstick A~ ly in ac~ h,.ce ~it~ the invention;
- Fig. 12 i~ a sche~atic d$agram of a , ~ostrictive suitable for u~e ~$th the invention;
Figs. 13A and 13B illu~Le one em~o~ of a stick gauge suitable for use ~ith the invonti~n;
Fig. 14 i~ an enlarged view in section of the cap ~s~ 'ly u~ed in an em~o~i _n~ of ~he invention; and ~ ig. 15 is an electrical 5Ch~ tic diagra~ of another suita~le e~ ol circuit for the invention.

D~ATr.Fn ~-5~Kl~lro~ OF TH~ lhvr.-LlON
With reference to Fig. lA, aircraft, parti arly large commercial a~rcra~t, have a plurality of fuel tanks 10 internal to the Ying structures. Although the invent~on is described herein with particular reference to commercial aircra~t, this is for ~-~ose~ of explanation only and should not be cû..~L~ed in a limiting ~ense. Those ~killed in t~e art ~ill readily appreciate that the invention can conveniently be u8ed with any aircraft or otner vshicle~ or stru~L~ that have li~uid contai~ers. The invention al~o is not li~ited to fuel tank container~ of volatile fuel, but can be used for ~ensing liquid quantity and level~ of ~any gluid type~ in virtually any container. The particular ~er.~o. used for deteoting the fuel level/quantity, such as, ~or exanple, a magnetoresi6tivs 6 21S~80 dripstick as de~c~ibsd in an eYe~plary ~4nner herein, is al~o a ~atter of design choice. '~hose s~illed in the art ~ill readily a~,eciate that the advantaqe~ and benefits of the invention can be rPali~E~ using any ~en50r that pro~n~e~ an electrical ou~t or y~o~ ce~ an output or ^Yhi hi ts a c~aracteristic that can be inte-~r~ed by elecL~ ic circuits in~ludinq c~p~itive, reOEi6tanCe~ acou6t~c and ~o on to name just a few. The terms ~liquid le~el~ and 'liquid quantity" a~ u6ed herein are intended to be understood in the$r br~adsst sen~e and are e~entially inter~h~e~hle ter~s. As is ~ell known, li~i~ level data can easily be converted to liquid quantity data, and vice-versa, when the tank or container Ai - -ional characteristics are kno~n. The invention is directed in a broader ~ense to a~a~us and ~ethodfi for re~otely ~nte~u~a~ing sensors that produce ouL~uL~; and is especi~lly useful with sensor~ that produce ~ Cor~
to liquid quantity and/or level in the fluid container.
In the embodiment de~cribed herein, each fuel tan~ or liquid container 10 includes one or more quantity/level ~ensors 12. For example, large co~mercial aircraft such as the Boeing 747 may u~e nineteen such sen~or~. Other application~ and containers ~ay use different number~ of ~ensors or only one sensor.
Each ~en~or 12 can be of any oon~e"ient design that i~
prefer~bly electrically interrogated.~ In other words, t~e particular sensor selected i5 optional for the de~igner, but preferably ~ill be a sensor that produc~s (or is ~ornDcted to a trAn~cer that produces1 an electrical o~L si~nal that COLI ~ 5~ ~L ~- to the quantity/le~el of liq~id in the container.
One example of msny of a commonly used ~en~or i~ a capacitive sensor in which a capacitive elenent c~a-J~- c~pacitance value in relation to the ~r .~..L iDcersion of the elecent in the liquid. Such a ~en~or i6 described, for example, in U.S. Pat.
No. 4,841,227 i~ued to Maier and com~only ovned by the A~s~ e or the pre&ent invention, t~e entire di~clo~ure of which is ~ u,~v,~Led herein by reference.

7 21~2~

The ~r~EFnt invention is partic~ ly ~ell suited $or u~e Yith a drip5tick sensor 12 that is co~only used to mechanically read fuel levels $n aircr~ft fuel tanks. In a cG.~ tional drip~tick deslgn, the dripstic~ 6ensor 12 ~nc~ ~ an ~lorg~ted linear body 14 that i~ vertically ~ounted in the fuel tank. For bottom ~ounted dripstick6, a ~ ic or ferrous tip 16 is placed at the upper end of the dripstic~. A ~agnetic ~lo~e ao ln ~he form of a collar is slidably placed around the elong~te body and float6 on or near the fuel ~urface 18. ~hen the g.u~.d crew pu116 the dripstick body out of the tanX, the ~~ ~ic can physically sen6e the po6ition ~hen the tip 16 e , , Y the floating ring 20. Calibrated ~arkings on the dripstic~ body thon ~ provide a visual reading of the fuel level and hence volune in t~e tank, ~hich infor~ation can be u6ed as a con$~nmation of on-hoard fuel level r~in~s.
The present in~ention provides a ~i~ple and accurate way to interrogate such a dripstick sensor without the need to me~hAnlr~l~y withdraw the dripstick fro~ the ~uel tank ~as will ~e more fully explained hereinafter Yith e~e~ to a sen~or such as illustrated in Fig. 4.) The modified drip~tick de~cr~bed herein, h~ e~, ca~ also be dual configured in a co..~..Lional - nn~r for ~anual ~ithdrawal in case a ~l.. A~nt manual h~r~t~r systeu i8 desired.
~ore generally, th~ugh, the invention contemplates apparatu zs and methods for interrogating many different types of sensor~
using a remote hand held unit.
As illu~trated in greater detail in Fig. lB, the sensor 12 (which in this case will be the modifi~d drip~ticX deccribed hereinafter) ic electrically conrle~ to a -~en~or elc~ru..ic 3~ c~..Llol circuit 40. The ~..L~ol circult 40 ~ay be ~i~po~ Ln a unit that also is u~ed to mount the ~ensor 12 in the tank. The cont~ul circuit 40 j~ol ~- a circuit that receive~
ele~L~. ~nDtiC e~ y 32 (Fig. lA) from a remote cu.,L~ol preferably hand held unit 34 and c~nv~L~ this e~c~yy to electrical power for the ~ù..~,ol circ~it 40. Thus, on-~o~d 8 21~2~80 electrical power does not need to be connect~d into the fuel ta~k, thereby r~du~ng electrical ~. ~ n the tank.
The cG~.L~ol circuit 40 further include6 a circuit that detects the variable para~et~r of the F _~ 12 ~e.g. the re~i~tance value or capacita~ce value a~ a function of pe~cer,~
i~ersion) and emit6 e~ectromagnetic ~ 36 having a characteristic that is ~odulat~d i~ relation to the ~l~id guantity andlor level detected by the sen-or 12. For -- le, the ~,.t~ol circuit 40 ~ay e~it elect~ Lic p~ e~ having a duty cycle or time ba~e - lation that co~ A~ to the llguid quantity detected. Other - lation and ~o~ing ~c~e~e~ can, of cour~e, he usod. The e~c~~' data may ul e -~ include information in addition to the liquid quantity. For example, the cen~or cGr.Llol cir~uit 40 can be used to ~co~ information 6uch as the type of ~ - u~ed, the type of aircraft it ~ installed in, ~hich sen~or oor~c~yo~d~ to the parti~lA~ circuit 40 and so forth. 5nG~ that detect fuel character~ StiCB o~her than quantity can also be inte~u~dLed if desired. Each ~nsu control circuit 40 preferably alDo e~its a digital code or protocol 80 that the data signal~ can be pro~lly detected and identified.
According to an important aspect of the pre~ent invention, the sensor cv..~ ol circuit 40 i~ re~tely energized and, in combination ~ith the remote co..L~ol unit 34, intcl~vy~-e~ the sensor 12. Preferably, the remote unit 34 i6 a small porta~le hand held unit easily used by ~luu~d crew~. When activated, the hand held unit transmits el~r~ - Lic energy 32 to the censor elect~v~-ics 40 wherein it i~ CO.I~el Led and stored as u~eful electrical energy~ This stored electrical ~.~e~ provid~s the po~er n~e~el to energize the F'- ~, 12 and al~o to energize the circuitry n-e~e~ to transmit the sen~or data and ide~tification back to the hand held unit 34 ~ia the - lated ele~L~r-~e~tic ene~gy 36. A detector circuit i~ the hand h~ld unit detectR the ~ ated ~eam 36, d- lAte~ the ~ignal to ~6~e electric~l signal~ contaln~ng the desired ~en~or information and fuel data, 21~2~
and if de~ired pr~-~ LL the infor~at$on on a visu~l dicplay 3 or in a~.oLhel v~L~t form.
A ~yste~ level approach to euch apparatus is illustrated in Figs. 2 and 3. A 6~ v~ ~v.,L,~l circuit i~ generally indicated ~ith the nuDe~al 40. The 6er-- ~v.,L,ol circuit 40 includes one or ~ore signal ~v~-4 ~1 lines 42 that c4n~.~ct the ~u.,L~ol circuit 40 to the 6ensor 12 (or alternati~ely a plurslit~ of sensor6 when the circuit 40 is configured to operate in a ~ultipleYed ~ode.) The signal cu.-L~ol line~ 42 ~ay, for exa~ple, be used to 6upply electrical power to a _e..~vl or to receive an o~ut signal from a ~en~or, or simply to CQ' ~ ~ct a ~ensor ele~ent (such a~ a variable _ nont) into a detector loop Yithin the circuit 40.
The ~pecif~c nature of the interface of the 6en~0r 12 to the circuit 40 ~ill be deter~ined by the t~ e of sen~or being u~ed.
In the de~cribe~ em~odi~ent of this invPnti~, the 6ensor u~uL
i8 es~entially a voltage or cu~ ~..L that ~vL~Qn~ to the re~istance value of the dripstic~ ~aqnetore~i6tive ele~ent. The sensor 12 vuL~uL could just as easily ~e the actual resistance itself of the ~sv -or~n~-Led by the leads 4Z to an i~~~~'~nne zo sensitive-detector in the ~v..L ~1 circuit 40. A~ another example, the circuit 40 could be optically coupled to the sen~or 12, or ~agnetically coupled to the 6ensor. A direct hard wired connection i~ not essential ~pe~ing on the type of sen~or being interrogated a~d the method of interrogation selected. The i~portant aspect i~ that the circuit 40 ie configured to interrogate or dete~ inP the sensor 12 ou~y~L condition after electrical po~er has been input to the circuit 40 by operation of the hand held unit 3~, ~hich condition ~ur~s~s~lc to the fuel level or quantity i~ the tank. Until electric~l energy is delivered to the circuit 40 v~a activat~on of the re~ote unit 34, the sen~or 12 and the circuit ~0 _re pre~era~ly and ~ubstantially de-energized.
As further ~e~esented in ~ig. 2, the re~ote unit 34 ~s re~otely ~ e~Led to the c~.L~ol circuit 40 via the tran~itted and received ele_L~I ~netic e..e~ si~nAI~ 32,36. T~e remote unit 34 circuitry i~ ay~,Gy~iately configured to transmit electro~agne~ic en~r~y, 6Uch as for exa~ple, photcelectric ~r.e}~
~uc~ as infrared light (32) to the c~..L.ol circuit 40, and eo receive photoelectric e..e~ uch a~ infrared light (36~ from the cG..~ol circuit 40. The re~ote cu,.LLul unit 34 is optically ~ L~ruu~h air to the coll~ol circuit via the light tr~n~ i ~sion alone, without the use of optic fiber~ or other llght conduits, or electrical ~r.~ ions thereby ~aYi 17,1~ the fl~vihility, portability and ~L~plicity of u~e of tbe hand held unit 3~. mu~, the term ~remote" as u~ed herei~ refers to ele~L~ netic coupling without the use of optical or electrical cc,.ne~Lion~ ~e~ n the ~ unit and tbe ~nCor ele~L~..ic6.
The cul,t~ul circuit 40 may be designed to perfor~ any number of function_ ' , 'in~ on the nu~ber and type of 6ensors being ~5 interrogated with each e-rcuit ~o. ~ , gene~lly the collt~ul circuit 40 will include at least the follo~ing functional circuits. An ~.e.~ rece~ver, such as a p~otodiode array 44 i~
used to receive the electromaqnetic ~ y t~an6mitted froD the hand held unit 34, and to cor.~_lL that e..~ into useful electrical energy. The type of device~ u~ed in the array 44 will, of cour~e, depend on the ~ L~l content of the electromagnetic energy used to link the h~nd ~eld unit 34 to the control circuit 40. Althoug~ infrared light i8 one of the preferred option~ it certainly i~ ~ot the only option availa~le.
Bro~h~n~ radiation such as fro~ ~hite ~un~Len lamp~, radio frequency waves and other ~e_L~al ~ands can be used for the electromagnetic energy. Whatever ba~dwidth i8 selected ~ill deter~ine the specific detector 44 used, which ~u~t be r~ ive vithin the ~ec~ral band of the electro~agne~ic energy trans~itted to the control circuit.
~ n the described exaople, the diode array 44 pro~l~c~
electrical energy in respnn~e to the received llght 3Z. A power ~torage circuit 46 receives and storeF thi~ electrical ~ r for use in powering the sensor 12 and the circuit 40 under the ~5 cont~ol of a po~er control ~e~el.Ce~ circu$t 48. The ~

ll 2152880 circuit 48 i~ de~ign~d to ~equentially ~u..L~ol the application of pover to t~e ~ 12 ~or 6ensors in a ~ulti~l~ e' de~iqn) via a ~e~r interf~ce circuit 50. Depon~i~g on the overa-l co~plexity of the 6en~or 12 and the circuit 40, the ~nterface ci~cuit 50 may be as si~ple as a SYitCh, a voltage level shifter, or ~ore involved BUch ~5 a uultiplexer, ~L~ r and ~o on.
Whatever functions are selected for tho circuit 40 ~ill ~be det~ ino~ pri~arily by the ~oount of electrical ~.~ th~t can be stor~d ~nd retrieved fro~ the storage circuit 46, and ho~ ~uch of a load the circuit 40 ~pli~ to the storage circuit.
$he ~ ut~ infor~ation i~ input to an ~co~er circuit 52 that ln turn i8 _ - Led to an ele~ ic ~ource 54, suc~ as an LED array and driver circuit. ~n general, the overall electrical load of the circuit 40 is pri~arily ' '~L on the po~er conBu~ption in the LED circuit, especially if the circuit 40 i6 expected to transmit the s~nsor data over a long di5tance to the hand held unit 34. ~h~ ore, sen~or data is p~eferably ~ oAfA in a digital ~anner eo that the source 5~ can be ~llr~
rather than con~n~?o~ly operated.
The hand held unit 3~ al~o includes an ~le~L,~ n~tic energy ~ource 56 which for convenience may be an ~D and associated driver circuit ~i~ilar to the cu,.L.ol circuit light ~u~e circuit 54. ~u~ ,, the re~ote hand held unit could transnit electromagnetic e..~ for p~oses o~ energizing the sensor using a di~ferent s~cL,~l band t~an is u~ed ~or the ~co~ energy transmitted back ~o the re~ote unit. A detector circuit S8 is used to receive the ~nco~ Rignal~ ~ro~ the ~ u~
~u"~ol circuit 40 ~nd to con~ert tho~e r~l~e~ into electrical signal~ that can be ~luC~ A and inteLy~Led. T~e detector circuit 58 can ~e a sinple photodiode or photoAic'~ array or other trA~ , and nay include ~iqn~l conditio~;ng circui~6 for a~plification, filtering and other 6i~n~l ~ru~_OOing functions ~ell known ~o tho~e skilled in the art.
The detector 58 Oignals are input to a centr~l p~ oce~ainq circuit 60 ~hich ~or convenience ~ay ~e a coh~ul circuit 12 2152~80 utilizing a ~iu~ 60r or si il~r ~oJ-L~oller. Di6crete logic and ~ignal ~rc~ ing, of ~uUl LQ~ co~ld al~o be u6ed. The c~ .LLolle~r 60 u~e~a~e6 a power a~nt~ul circuit 62 that 6~1tches the light ~u~r~a 56 on and o~ at a~.op iate ti~es. The ~u-ce 56 i6 u~ed, a~ ~tated, to 6upply electrical ~ne~y to the sen~or circuit 40. ~he 6~ce 56 c~n be de~igned to be operated contin~ ly during a e~l-6G~ int~r O~aLion ~e~ion, or can be ~u~..cd off when t~e hand held unit is ready to receive the ~ E' light r~'~~~-The co.. L~oller 60 i~ ~G~a~med in a cu~ Lional manner to inte~le- the received data ~ro~ the sen~or 12 and cu..~ælL that data into an output, ~uch ae the visual display 38 u~ed to di~play fuel level, quantity, sen~or ~' e~t~ fication, plane identification or any other data tran~itted back to the remote unit 34. The cor.~ller 60 also ~onitor6 an operator interfaae circuit 64, which ~ay be .ralizc~ in the for~ of an al~h~ -ric keypad optionally provided ~it~ 6pecial function key~ and so forth as is well known. The operator i~terface can be u~ed, for example, to co~ ul actuation of the light so~Yce 56, as well as to input cG..Llol data such as the type o~ plane, which sen~or i-~being acoe6s~, and so on when 5uch information i6 not transmitted by the on-board 6ensor.
With refe~_..ce now to Fig. 3, a suitable o~erall ~y8te~
functional flow diagra~ for the apparatus illu6trated in Fig. 2 is provided. Again, t~i6 flov diagram is only intended to ~e exemplary, the actual function~ and ~tep~ being performed by the fuel gauging systen being ultimately deter~ined by the complexity and data requi~ s specified for a particular application.
At step 70, the co..L~oller 60 turns on the ~.~ u~e 56 as instructed by the - `-nic by activation of tbe hand held unit 34. The source 56 transmit~ el__L~ ct$c en~ly~ toward~ one of the drip~tick een60r6 by neans of the han;o -i ;nq the han~
held unit at the a~oc~ate~ uu..~l circuit 40. The detector array 44 i~ PYpose~ to the incident L.~e~ uch a6 through an optical vindow (not shown) that 6eal~ the ele~tr~ cs 13 215288~

from the environment exterior to the ~ing or tank. T~e ~.,L~ol circuit 40 ~ ~c the received electroDagnetic er. y~ to electrical ~ and in-Dr~u~aLefi the ~enrD~ 12. The 5en50r ~uL~t is then ano~ -' and t~an~itted bac~ to the hand be~d unit via the ~odulat~d ~our~e 54. Thu~, at step 72 the detector circuit 5~ receives the onr~A-' signal 36, ~rc_eF~e~ t~e fii~nAlc as required, and at step 74 t~e ~Gn~.oller 60 determines the pulse ti~ing characteri~tics to inte~e~ the ~ - _ 12 outputs.
The col,Lioller 60 al~o ~cc~e~ the data signals ~ith the ~ncQd-lnformation ~uch a6 the drip6tick number, aircraft type and ~oon. At ~tep 76 the co,,~ ~ller, ~y ~ean6 of a~ro~iate l~o~l~r table~ and algorith~s ~U~ l L~ the ~e~e~ si~n~Js into the de~ired information ~uch as fuel volu~e, level, sen60r number and 60 on, and at 6~ep 7~ pl~y6 the requested inforDation to the - --nic via the di~play 38, ~ich ~8y be a visual display, printed data, r~_u ~-' data and ~o forth.
With refe~ c~ next to Fig. 4, there i8 shown a drip~tick ~en~or that ~as been ~o~ified for use with the remote inte~.oydLion or direct int~u~dLion by on-board electronics approache~ of the y e-~e..~ invention. For clari~y, Fig. 4 only illustrates the operative portion Df the ~ensor in ac~ordance ~ith our invention that detect~ the fuel height in the tank.
Other part~ of the drip~tick can be conventional in design and are ~ell kno~n. The sen~or 12 includes the elo~Jæted '- 14 which ~ay be, for example, an alu~inum,tube 80. Within the tube ~0 is a precision wire wound resistor 82 which extend~
substantially along the entire portio~ of the tube B0 used for detecting the fuel height or level. The float Z0 is ~;~poa~
around the tube 80 a6 a collar, and retain~ an actuation magnet 84. As the float noves up and down in relation to the fuel level 18, ~he ~agnet 84 c~lces spring fingers 86 that are part of a cQn~tive ~trip BB to contact the wire resi~tor ~2. A magnetic piece 89 may be provi~ed to insure the fi , ~ ~6 ~Lu~l. out o~
contact from the resistor 82 ~hen the ~loat i~ not aligned witb t~e fingers. one end of the resistor 82 ~L~e~ a~ a ~en~or teruinal 90 and th~ ~on~n~tive ~trip B8'6~rve6 a6 another sen~or ter~inal 92. Thu6, the re~istance bet~een th~ ter~inals 90,92 directly c~ A~ to the peresnt immer~ion of the tub~ B0 in the fuel, or statsd another ~y, ~irectly co~ p~n~l~ to the ~u-1 level/qu~ntity in the tank. An inF~ tive layer 94 can be provid~d ~t r t~e tube Yall 9C and the internal parts of the magnetoresi6tive 6en~0r to ~ .L the tube 80 from electrical`ly ~hort circuiting ~he re~i~tor 82. Thi~ par~ G~vr 12 c~n easily be inter~o~a~ed by ~i~ply applyinq a voltage or c~rr~nt across the ter~inale 90,92 a~d determinin~ the re~istance value~
A particular 71~.Lage of this ~o~ified drlp6tick ~en~or i~ that it can al~o be used ~anually by the ~ cre~ for verifying the fuel level rea~ as with a co..~ ional drip~tick. Thus, the mDdified dripstick can be used ac a direct field replao e~t for co..~ ional drlp~tick~. ~160, the _ ~u,~si6tive ele~Qnt can advant~eo~ly ~e hardwired to the on-board electronics if ~uch ~onitoring of the drip~tick reado~ is d~si~ed.
In F~g. 5, there i5 shown one exa~ple of a circuit that can ~.ve..iently ~e u~ed for ~.~r~ col,~e~ion and po~er cu..L,ul in Zo the sensor co..~,~l circuit 40 with exe~plary ~ value~
being provided. In this particular arrange~ent, the detec~or array 44 i6 positioned near an optional len6 100 that collLmates light energy 32 received fron the re~ote hand held unit 34 th~ou~l- a window 102 which ~ay be flush rounted with the ~ing Z5 under~ide. The array 44 preferably includes a plurality of photocell6 104 that co..~r~ incident light ~e~ into voltage and O~r r el-L. The cells eould be u~ed in the photovoltaic, photo~u~er,~ or both modes. The hu~ber of photocell~ 104 ~sed will be det~ t~e~ by the characteristics of the photo~ell used, as well as the voltage and c~arglng requirement5 of the overall ~ rol circuit as dictated ~y the circuit' 8 power reguire~ents r,~e~-' to int~L~vya~e the 6enoor 12 and transmit e- eded light si~n~ls b~cX to the hand held unit 34.
The photocell~ 104 are C~ to a circuit charge storage car~citûr 106 tbrough a rectifying diode 108. The array 44 i8 al80 o~nn~ted to ~ LED/~river (54) storage --F-~itor 110 throug~
a 6eco~ rectlfying diode 1~2. S-~ala~e 6torage cAp-~itor~ ,are pre~erred for the LED and COnt~ul circuit ~unctions due to their ~,ue~Livs load e~fect~ on the o~erall charging reguire~ent~.
S For exa~ple, the circult ~torags ~p-citor 106 can be smaller in ~any applicat$ons and thu~ charged quickly for fa6t -co~ to the r-nf~ 12. Al60, by having the LEDB ,~ ~L~ ~ro~ a 6ep~rite capacitor, the load effect6 of the LED~ ~ill ha~e le ~ infl~nre on the ~,,u~,~Lion of the ~.,~ ol circult ~ ~ Ls used to inte~oy~e and ~n~c~ the s~nsor 12 data. Tbe LED capaoitor 11 ~tore6 a DC ~upply voltage V~ 114 at an ~uL~uL node lI6, ~hich is ~ ed to the LED~Driver circuit 54 (Fig. 2). Note that in ~he prefer~ed ~o~i L, the DC supply to the LED/D~i~er 54 is ~ain~e~ for as long as the capacitor i~ charged by light received fro~ the re~ote unit 34, or until the ~Ap~-~itor is ~i~chArged by ~pe~atlon of the TFn circuit 54. The circuit ~torage c~racitor 106 ~tore~ a DC ~upply volt~ge that appears at node 118 with ~ L to the common ~Lu~-, 120. ~ po~er s~itch circuit 122 co~ ec~s the stored ~.~ fro~ the capacitor 106 to a V~ terminal and V~ terminal 12~ which are conn~cted to the sensor interface circuit 50 (~ig. 2). The circuit 122 o~eld~es in a conventional ~anner to ~wi~ch on the G~ t t~ansistor 12~
when the voltage stored on the capaci~or 106 re~che6 about l5 YDC, and ~witches the transi~tor 128 off ~hen the capacitor 106 ~ic~hA-ges to about +2.2 VDC. The ~itch circuit 122 provides a lo~ impedance output for the circuit voltage ~upply, and also prevents operation of the control circuitry until su~icient energy is stored in the capacitor 106 to assure ac~ul~Le data can be transmitted back to the rerote unit 34.
In Fig. 5A there is shown a.. uU._~ and ~i~pler circuit t~at can ~e u~ed for _~e~yy cu..~ ion and ~torage when i~olated LED
and cG,.L~ol circuit ~upplie~ are not~ rle~ ~with like co~ponent~
being gi~en like reference nunerals follo~ed ~y a pri~e'). In this circuit, the detec~or array 44' corlv~r~s the ele~L~. , Lic ene~y into electrical er.el~ that is sto~ed in the ~ain ~torage capacitor 106' via a recti~ying diode lOB~. When the stored voltage r~ a ~ e~er ined threshold, an ~u~uL tran~i~tor 12B' s~itche~ on and the supply voltage appear5 at the V' and Vr ter~in~l~ 124', 1201 and ic coo~ ed to the LEP/Driver circuit 54' and the se~ nterface circuit ~0'.
Rererrinq next to Fig. 6, there i6 6hown a ~et of circuits (A, ~ and C) that can cG~ ntly be u~ed to detect the dripstick ~ 12 output and to ~ the ~4~ut for transmission to the re~ote cGr.L~ol unit 34. The V~ and V
1~ cupplie~ ~ho~n in Fig. 6 are o~-. f--Led to the uut~L node~
124,120 of the ~upply circuit in Fig. 5. ~he top circuit in Fig.
6 is a simple voltage ~c~ ing circuit that connects the V~ and V~ supplies acros~ a preci~ion refe~n~s re~istor 140. A
reference resi~tor i~ used in thi~ c~se ~sc~ he ~ensor 12 of thi~ exa~ple is a ~agnetoresistive ensor having a resistance value that i~ the para~eter of inte~est. The voltage acro~ the reference resi~tor 140 ~ es a ref~ e ~UL~ that is converted into a neqative reference voltage, -Vref, by an inverting amplifier 142. A ~ecnn~ inverting amplifier 144 configured for unity gain ~o.J~oe~ a positive re~e~e..ce voltage, +Vref ~ -The ~iddle circuit in Fig. 6 realizes the sensor interface circuit 50 ~ig. Z) and is used to tr~n~A~ the ~en60r 12 output into a useful electrical ~ignal. The V~ and r ~upplies are co~nected acro~ t~e 6en~0~ resistance via th~ signal line~ 42 (Figs. z and 4). This produces a ~en~or ~u~len~ T~ _, which is co~ r~ed to a voltage, V~en~r, by anot~er a~plifier 146.
The v0ltage5 +Vref~ ~Voen~or and ~Vref are input to the lower circuit in Fig. 6, which realize6 the en~ circuit sZ (Fig.
2). The ba~ic fun~tion o~ thi6 particular e~eo~ng ci~cuit and enco~i ng schcme is to produce a series of ~ DR having a time displac ~ ~eL~_E-~ P"1~Q that C~ A~ to the 6en~0r 12 output re~A; n~ . Such a circuit and ~n~oA i ng sche~e are fully de~cribed in U.S. Patent ~05. ~,075,631 and 5,077,527 both ir~ d to Patriquin and ~ ly owned by the assignee of the present invention, the ~ntire ~cln-~re~ o~ both patents being f~lly in~u-~ulated herein by refe~nc~. Refe~- ~e to the~e patents ~o~ be ~ade for a detailed explanation of the R~roA-r c~rcuit.
Easentially, a ra~p ~enerator 150 is u,~ed to ~du~e a ~oltage ramp signal 15Z. The ramp generator is ~u..~.iently realized in the for~ of an integrator amplifier. The rA~p signal 15Z i9 input to one input 154 of a ~ ,- a~or 156. Ihe other input 1S8 to the comparator 156 is ~ Led to a ~ult~r~eYDr or ~ignal sYitcher circu$t 160 ~u--L ull-d by a ti~ing co~t~ol circuit 162 which can be realized with a counter. The c~n~rol circuit 162 sequentially applie~ t~e +Vr~f, ~V~en~or and ~Vref tû the comparator input 15~. The part~ 6equence only reguires that the ~e.~G~ volta~e be applied temporarily ~ ecn the t~o refe.e..~e voltage~. The co~parator 156 output ~ha~ 6tate ~hen the ramp voltaqe roa~hP~ the level of the applied ~ignal to the other 4_,~rator input. After the comparator change~ state, the COl~t~ ol circuit switches in the next signal to the comparator input 158 50 that the comparator 15~ output is a serie~ of 6hort pulses. The ,- ~Lor output 162 i~ c~ ~e~ed to the LEDlDriver zO circuit 54 ~igs. 2 and 8.) With reference to Fig. 7, there i8 sho~n a timing Ai~.n;
for typical pul~e~ output from the ~ o~. circuit of Fig. 6.
In this case, the ~o.l~oller 60 ~Fig. 2) turn~ off the light source 56 after sufficient time ha~ passed ~a~ at 170) to c~arge the storage capacitor~ 106,110 (Fig. 5.) At ti~e Tl, the comparator 156 G~uLs a first pul~e that ha~ a leading edge dete. i n~ ~y the value of the +Vref signal. The secon~ pulse has a l~-~ing edge at time T2 and this c~ 5~ ' to the value of the sign~l 3~ Veen~or The third pulse has a leading edge at ti~e T3 that is deteL inefl by the value of the ~vr~f eignal. aPc~ s~ the ra~p voltage VR~ i6 a etable conetant, and the ref~lelJ~e voltagee +Vr~f and -VrRf are ~table conetant~, the tL~e delay ~e~._en the 1P~jn~ edgee at Tl and T3 ~o~ be a fixed refere~.ce ti~e. The time o~u~ence of leading edge T2 ~hich CO~ O~ S to the -- - data will vary ~ith the 9~n6G~ 12 re~i~L~r.~e value and t~U~ CG--8-~na to the fuel guantity/level in the tank. Thus, the ratio (Tl-T2~/~Tl-T3) define~ the ~ractional im~ersion of the sen60r 12 in the fuel.
It vill `oe a~pLe~iated by those ~killed in the art tbat ~n the ~pecific : ,le de~crlbed herein, Ir ';~g edge ti~ing i~
used for ~n~-o~ . u~ " other timing 6~ cec can be us`ed just as cu~ r.iently.
With refel6..~e to Fig. ~, there i~ d~own a ~i~ple circuit for interfacihg the ~-.c~' 52 to the LE~/Driver circuit 54. The V~ and V~ supplies are cQn~e~ to t~elcuLye~ ng terminal~
ll6~lao fro~ the 5~UL _, _ circuit in Fig. 5. An LED, or alternatively a" array of ~ED~, are series ~ c~ed with a svitch lB2. The ~witch 182 has a cor.~ ol input ~84 that i9 c~nn~Gted to the output 162 of the ~ co~parator 156. T~u~, the ~witch 182 i~ r-lc~ on and off by the e..~ a ~ ses fron the comparator 156, thus ~uLL~ ngly pul~inq the LED 180 on and off. A len~ 136 collimates the light ~roo the LED 18~ and transmits the light p~lses through a window 18B toward~ the hand held unit. The lens and window are, of cuulse~ optio~al ~F~ on the particular application.
~ ith ref~.~..ce to Fig. 6A, t~ere i5 shown another embodi~ent (with like ~ - Ls beinq given like refelence r,~ ~ ~18 followed by ~ pri~e') for an ~0~? circuit suitable ~or use with our invention. In thi~ example, an output comparator 156' i~ u~ed to produce a serie~ o~ p~ e~ having a ti~e domain di~place~ent that corre-~nA~ to the s~nsor 12 uuL~u~ data. A
conL~ol circuit 162' i~ u~ed to switch seyue--Li~lly to the comparator (by ne~n~ of a ~witc~ing circuit 160l) eiqnal6 from a pair of one ~hot timers 190,192. The first ons shot prnA~ e6 a pulse sdge at a ti~e that cu~ to a re~ere,-~æ re~i~tor 140', and the _e ~,' one shot 192 y~ A a pul~e edge that cot.~6~0~ to the ~en~or 12 re~istnnce value. The firbt ons ~hot ~ay be armed from a ~ignal p~ lu~æ~ by the en~L~ 6tor~gs circuit 46 (Fig. ~), and the ~econ~ o~e ~hot ar~ed by the pul~e 19 215288û

d ~y the refsren¢e one shot. As in the other de~cribed hodirent~ the co~parstor output 162' i~ a seriefi of pul6e~
.c~r' ~ith t~e ~en~or 1~ n~, ~8 descri~ed hereinbefore, the hand held ~nit 34 includes a~.u~rlate circuitry fo~ tran~ oinq the ~ light rec~ivsd from the ~u..~ ~1 c~rcuit 40 by ~ ~ns of the detector circuit 58.
The c~..LLull~r 60 can be e_sily ~Q~y~o~med to ~ Ate the rat`io (T1-T2)/(~1-T3) to detc~ ;ne the fuel level and quantity.
Al~ho~yh not ~hown in detail in the Figure~, the ec~
circuit 52 ~ay inc~ a recnn~ or ~ore r~ p , _~ort6) and sociated circuitry to generate a pulse ~erie~ that enc~e~
ident$fication data ~uch as tbe sen~or 12 ' , locatlon, plane - identifier and ~o on. Alternativsly, the ~ could tran~it one or ~ore digital ~ords (for eXample by use of a y,o~ oable R0~ or other ~emory devics) to the hand held unit 34 before ths s~nsor data ic tran~mitted, with the digital vord~ being e data of interest to the ground crew.
With refe~ e to Fig~. 9A and' 9B, there $5 ~ho~n in si~plified ~orm another ~ of the invent$on that includes a fully integrated magnetostrictive fluid le~el ~ensor and ~anually ~erated stick gauge. An ad~antage of thi6 e~bodiment is the u~e of the magnetostrictive ~ DUL that can be interrogaeed electrically to deter~ine the po~ition of a float.
The 3agneto~trictive sensor i~ contained ~ithin a small envelope that can acco~cod~te a stick gauge a~ ~ell, thus providing in a single unit both an electrically reAA~h!e sen60r a~ well a~ a y readable ~tick gauge. ~6 ~ith the earlier de~cribed hoAi -rL~ herein, the . eLostrictive ~en~or can be interrogated by h_rdwired ~ ~L~ion (such a6 by the o.. Lo~rd electronic~ for exa~ple in aircraft applicationD), and/or remotely ~y use of the remote ~and held unit. T~e sntire ~8~ ` ly of t~e magnetostrictive e~rDoL, DtiC~ gauge ~nd ele~onic~ tfor re~ote o~ hardwired inte~,uy~ion) are ~elf-cont~ in a 6Lngle p--~r~e that can'fit Yithin the di~en~ions 35 of a co..~ ional fluid gauge housing, thu~ per~itting si~ple and direct form, fit and function repl~- ~ of a c~nv~ ional ~luid level proke.
ln 5 --_al, th~ ay~aLaLul~ 300 iDClUdeB a ~ain h9~Ci~J 302 that is installed in the fluld c~nt~;n~r (not sho~n). T~e hou~inq 302 typically i6 ~ade of alucin~m, s~Ainles-q ~eel or other suitable non-~agnetic material that ~ill not be ~-~?, -~ by the fluid in the container, such a~ ~et fuel. ~`
An ann~ll~r float ar- ~ly 304 is ~e~ ~.d the housing 302 as a coll_r and ~li' along the bousing at the level of fluid in the container. The float assembly 304 holds a ~agnet asseibly 306 which provides a ~echanis~ for detecting the pos~tion of the float as will be described hereina~ter. The magnet assembly ~y inr-~ '~ one or ~ore r$ng ~agnets or other s~itaole &~,ge~ent of ~agnets.
A dripstick ~ 'ly ~nit 308 i~ di~Fo~ ~ithin the ~o~1ng 30Z, and in this ~ bodi ,~ includes a -Lostrictive =---350 and fitick gauge 31~ that are ir.Le~Led into a self contA1r~
unit. The sensor/gauge dripstick unit 308 is A~a~te~ to ~lide ea~ily ~ithin the ~ain hou~ing 302 ~o that the ~agnetostrictive sen~or can be partially or fully withdrawn rro~ the hnl-~in~ 302.
T~e ~tick gauge 318 is al~o adapted to slide easily with ~es~e~L
to both the housing 302 and the magnetostrictive ~en~or 350.
The unit 308 include~ a cap ~c~ ~ly 310 tha~ can be ~ated to a mounting '-- 312 ~uch a~ a ~lange ~or eYample th~t can be part of the main housing or part of the container ~L~Luue.
~hus, when the ACC_ ~ly 30~ is fully inserted into the housing 30Z (as illustrated in Fig. 9B~, it is held in place by the mated cap ~si 'ly and ~ou~ting 312. This can be, for example, a threaded ~ ment so that when a n~lal reoAin~ of the stick gauge is desired, the cap ~C~F `ly is uu~ d from the housing and the magnetostrictiYe sensor can be withd,_ ..from the housing ~in most cases the sensor will ~e substantially ~ith~,_-n but not completely ,~ .~d from the hn"Ging) B0 that the ~tick gauge can be Aon~ed and vis~ ly ~ead.

21S2g80 Ibe drip~tid~ ~6~emb1y unit 30~ ~ a ~elf-cont~n~ unit th~t '~nc'~ es th~ l agnetOE:triCtiVe S:e..B~, a ~tic~c gauge and th~
elc_-.ol~ics for u~ Ling the ~a~J~G~LLictiv~ as well as for the re~ote inte~u~ion vhen 1~cl~de~. 5he electronic~ alao include~ the circuit~ describ~d ~ith 1~ ~e ~ to the other ~ for c~ ing received ele~ tiC energy into useful electrical e..~l~y to power the ~_ ~o~L~ictiVe sensor.
In this ~anner, electrical Ln~y~ cs~-~ in tbe a~e~bly 30~
only during actual rea~iry6. When the ap~ u~ 10 ic Opt~ lly hardwired to an on-board fuel gauging ~ , provi~ion can be made to apply power to the ~agneto6trictive - nr,c~ only as n~Pd~d during int.~lG~ation of the 8e~0~ -With re~erence to Fig. 10, we sho~ in ~ e ~ive a ~oredetailed illu~tration of the apparatu6 900. The housing 302 and float ~ -r~ hly 304 are ~iCpo~e~ in~ide the container or tank nc~
(partially shown~. The ~ovsing 302 i~ rlgidly mounted in the container ~uch a~ to a mwunting flange or wall of the rQn~in~
and in a ~ - ally vertical orientation. Altl-- Jl tbe exe~plary em~Ddinent herein sho~s a botto~ ~ounted arrange~ent, tho~e skilled in the ~rt will readily appreciate that ~he invention can be co..ve,liently adapted for a top ~ounted arrangement.
The housing 302 is provided with a male threaded bo~ 3S~
that threadably ~ate~ vitb ~o~ es~cl~Aing fe~ale thread6 in the mounting flange or other suitable structure on the container.
The cap ~cc- ~ly 310 is at the lower end of the drip~tick ~r~6~ hly unit 308, which i6 ~ho~n in a partially withdrawn po6ition in Fig. 10. The cap ~5~ 'ly 310 includes a ~ale threaded ring 315 that ~ates with a fe~ale threaded re~tacle on the container mounting flange or the hou~ing, for . ,le.
~hi~ allow6 the dripstick ~r-~ bly 308 ~o be fully in~erted ~nto the container and loc~ed into place ~y the tl~. ~c' ~n~ . 'r~-The unit 308 can be withdra~n from the container by ~i~ply unscrewing the cap as~embly fro~ the ~ounting flange and Eliding the unit out of the ~ain h~--Qinq 302.

The dripstick ac~eDbly unit 308 ~ r&lly include~ the cap ass~nbly 310, an elongated, rigid and s~ ble tube as~e~bly 316 and a 6tick gauqe 318. The tu~e as~Dbly 316 contain~ an elongated ~agnetostricti~e sensor therein as ~ell as all the ele~ ,ics n cded for o~ ion of the e lF,~_ including a trAn~r~V~r circuit for remote interrogation ~not ~hown in Fig.
10). If ~eedcd for a parti~lA- ~pF~ tlon, the ele d~o..ics can be located ext-rDal the a~sembly 30B. The cap ~r~" ~ly ~10 includeg an end piece 3ao t~at pro~ides ~ Q~ to a photoccll array and LED for ~ireless communication L~ _en the dripstick A~ ly 308 and a re~ote cu..~ol hand-held unit such as descri~ed hereinbe~ore. ~he dripstick aa6embly 308 i~ t-hu5 a completely ~elf-~ontained ~luid level sensor t~at can be remotely interrogate~, hardwired interrogated or manually ~nt~L G4~ed to dete~ inP the position of tbe float ~c- ~ly 304 and hence the fluid level in the container.
In this - ho~ t, the magneto~trictive sen~or 350 and the stic~ gauge 31B both function ~ith re~pect tD the Ra~e magnetic fl~at asse~bly. m ose s~illed in the art will understand that the ~igid tube 316 could also function as a ra~ual dripstick 6uch a6 illustrated in ~igs. 9A, B (in an aL~ , ~ent similar to the earlier described e3~0~i L in which the ~ toresistive ~e s~
was dispose~ in~ide a housing that function-d also a~ a conventional manual dripstick) by provid$ng the tube 316 with gradations, so that the separa~e sticX gauge 318 could be omitted. As a further alternative, the stick gauqe can ke integral with or permanently affixed to the tube 316 ~or t~e 6a~e purpose of ucing the rigid tube as a sticX gaug~. u~ v~, in so~e application~, the weight of the ~FF~ b~y 308 will be 33 sufficient as to preclude the use of such an a~l J~ent (as ~ill be explajned hereinafter, the -n~al sticX gauge u~e~aLes during a ~anual reading by having the gauge cd~Lu~d at the upper end thereof by the ~agnetic float assembly ~Ce6s weight can cau~e the assembly to drop past the ~loat ~enting an ac~ra~e re~ing)~

23 2 1 ~ 2 8 8 With refer~ to Figs. llA-C, the dripotick ~ ~ly 30B
is 6hov~ in elevation in Fig. 11~, in longit~ n~J crose section in Fig. llB .(rotated 90 degree~ about t~e longi~u~inAl axis comp_red to Fig. llA), ~nd a partial top ~n~ ~i~Y in ~i~. llC (to sho~ ~o ally t~e ~D~ 6hape of the tube 330). ~he ae8e~bly include~ an outsr tube 330 ~ich, as best oho~n in Fig. llC, i5 in the shape of a ~D~ to pro~ide a generally rl~t surface 3~z.
It ~ill be noted t~at in this embodiuent, t~e entire unit sho~n in Figs. llA-C i5 fili~able ~ithin the ~ai~ houfii~g 302, The D-tube 330 is crln~ed at one end to a 6~ivel ball mechani~ 334. The ~ n~sm includes a ~f~e,dlly t~hvl~r cup 336 that i~ attached at one end or ~ensor end to the D-tube and at the other end to a 6wivel ball 33B. The ~all 33B is pivotally ca~L~red inside a kall socket ext-nsion 3~0 on the cap a6sembly 310. The ~all and ~ocket arrange~ent i6 providcd to allov ~or mounting ~J~nges on the container that are not exactly tralls~ e to the longit~l~in~l or vertical axis of the D-tube 330. The swivel ball 338 is provided v~th an axial bore 3~2 th~ou~ll whic~
vire~ can be routed to the nagnetostrictive sensor ~ ly and ele~ru.,ic~ circuit board from the photodiode array and LED (a~
explained in greater detail hereinafter).
The ~ ostrictive sen~u~ as~e~bly 350 (~or clarity ohown in a si~plified manner in Fig. llB) is an elQ~ted unit that ia generally ~isFn~e~ AYia~ly withln the D-tube 330- m. 6en~0r assembly 350 includes an elongated body 352 and a receiver unit head 354. The recei~er unit 354 contains the various com~n_rl~s used to apply a~ electric cuL~enL pulse in the magnetostrictive element a~d for detecting the arri~al of an acoustic pulse generated by the interaction of the ~U-~ell~ pul5e ragnetic field and the -, -tic field a~sociated with the float 304. A~ ~ho~n in ~igs. llA and llB, the upper distal end 356 (distal from the sensor end) of t~e ~ o~trictive ~n~ul body 352 extend~
so~e~hat L_~o.ld the upper end of t~e D-tuhe 330. A ~pring load retaine~ pin arr~-~o~ t 358 ~i~pose~ at the Upper end 35~ ~an z~ 21S2880 be used, ~or exa~ple, to posit$on t~e upper end o~ the D-tube in the hou6ing 302.
In ~urther a_c4,1ance Yith the invention, the elon~-ted D-tube al~o retains an ~ JrL~ printed circuit board and A~6cciAted ele~L-u,.ics 360. The ~idth or the elongat-d cilcult boa~d 360 c~n be sized to ~ust fit Yithin the D-tub~ er.
The circuit bcard carrie~ all the lw L~u-lic~ n~e~ for operation of the ~agnetostrictlve sensor, 8s well as t~e interface circuit~ for the wireless tr~sc ~ver link ~ith a re~ote unit. A~ter all the conp~.cl~Ls are pocition~ inside the D-tube, the entire ~s~ hly of the sensor 350 ~nd printed circuit board 360 can b~ potted inside the D-tube u~ing c~ ional - potting ~a~erials.
The cap as6e~bly 310 i6 pro~ided with a key 610t 362 ao that a sc,~ iver or other suitable tool can be used to UnSCreY the ~ap ~Frihly fro~ the housing, whereby the op~rator c~n gra~p the cap as~e~bly and pull the entire d~ip~tic~ asse~bly 308 out of the ho'-~7 (or 6i~p1y allo~ the a6se~b1y to drop under the forc~
of gravity). The retainer pin as~e~bly 3S8 can co--~2l-iently be adapted to ~e~n~ the unit 308 from ~c ,letely f~ ng out o~
the hou ing onto the g,ou~d, by engagin~ with the mountinq flange or other suitable ~tructure on the container, while at the Sa~e ti~e allowing for complete re~oval o~ the unit fro~ the if 80 desired.
~e ~agnetostrictive ~en60r ~cs~-'ly 350 i~ an integral unit that includes the ~longated ~en~or 352 and a receiver head 354 located at one end of the sensor ~ody 352. The part~ r type of magne~u~L~ictive sensor selected is a matter of de~ign rhoire~
In the exemplary : ~o~i ~ of ~ig. 12, th~ ~en~or 350 ~ e a ~agnetostrictive wavP~ 3C4 co~Yially ~ F~ e a ~tainle~ steel she~th 366. The wav~guide can be 5U~OL Led in~ide the ~heath by a l.l ~l of .~ ~r~ 368. The di6tal end of the ~heath i~ closed by a br~ plug ~70 that al~o ~erves to electrically c~ e~L the waveguide 364 to the ~heath 366. In 35 this nner~ a ~ pulee can be applied to the waveguide by 25 21~2880 the el~L~onics, and is cQ~ ted by the waveguide 364 to its distal end a~nd l~Lur - to the ele~L,~ic8 via the sheath 366.
A nagnetic field is pro~u~P~ by the ~u~ pulse along the length of the ~ ~
When the magnetic field ~ ciated ~ith the ~u~ t pulse interacts with the magnetic field of the pen~anent ~agnet 306 in the ~loat 304 (~hich e6sentially o~ ~on~u.,~-Lly with t~e ~u~rænL pulse), a tor~ional acoustic pul~e is initially in~
at the point of interaction by the ~aveguide 364, and thi~
acoustic pulse travels back along the ~ it'- 364 to the receiver head 354 where it is detected by an acoustic pick-up 372. The time delay rrOm ~rrlic~tion of tbe ~ pulse to ~ detection of the fir6t acoustic pul6e t~us c~e6~ to the position of the float relative to the receiver head 354.
Si~Ul~An~o~ ~ith thi6 dl~ect acouRtic l~L~ pulse, an induced acoustic pulse also travel~ towards ~e distal end Of the waveguide where it is reflected back to~ards the receiver head and is detected by the acou6tic pickup 372. ~he total tiDe delay~ fro~ application of the ~u~ pulse to receipt of t~e direct and reflected acoustic pul~es can then be u6ed to calculate the relative poæition of the float ~long the length of the waveguide ~en~or body 352 based on the fact that the total distance tra~elled by the reflected pulse and the direct pulse is equal to two ti~es the length of thS wa~ . The ~peed of ~ound along the ~aveguide can be easily o~itted ~rom the calculation by ta~ing a ratio of the direct pulse time ~ea~urcment to the sum of the time mea~ 5 for the reflected or second pulse ti~e ~easu~ and the direct pulse ti~e mea~e~- ~. This ratio is thus inherently self-compe~sated, ~or exa~ple, for Y~-Jr~de ~peed of sound.
The ele~L.onics on the circuit board 360 can ke used to apply ~ er,L pul~es to the va~eguide 364 u6ing cu.~r.L$onal ti~inq circuits and pulse ~hapinq circuits. The ~aveguide is c~n~ted to the circuit board by ~per wires in~ide the D-tube 330 ~not ~ho~n). The receiver 354 convert~ the detected acoustic 26 , 215288~

into cu~ u~ing electrical ~t~n~a,l~ that can ~e sent to an on-board f~el gauging ~yste~, or c_n be u~ed a~ the 8en~0r input sig~al~ to the ~ireless reuote i~ u~ation npparatus previou~ly de~cribsd herein (6ee Fig8. lA and 2 and the ~iR~ion related thereto~.
The particular de~ign of the ma~n~l- L~ict$ve sensor 350, in~]~lAin~ the receiver unit 354, can be c~ r.tional and wIll ~' ,~ ' on each partirlllar ar~ ation. These type~ of ~er.~o~l, ~-/e~, are ~ell Xnown, such as describsd for ~ ~ ,le, in United State~ Patent ~o. 3,B98,555 is~ued to Telleraan. Suitable e~GaL~ictive _-~ul6, including the ~e¢ei~er unit 354, are av~ilahle from ~TS Syste~s C~OlaLiOn, S ._`a ~$vi~ion, r~ rch Triangle Park, North ~arolina. In t~e exe~plary ~ ent herein, the waveguide 364 is u~ed ~or both the cu~n~
puls~ and the tor6ie~al acoustic pul~es, but thi~ is but one eYa~ple. ~any differen~ types of ~agneto~tricti~e ~en~u~ can be u~ed.
A part~ r advantage of the exemplary de~ign i~ that it can ea~ily interface ~ith the re~ote interrogation apparatus 34, ZO 40 h~C~uce the electrical signals produ~ by the receiver un$t 354 in ,~ e to the detected acou~tic p-l ~D~ are simply separated in ti~e in relation to the position of the float.
The~e ~ignal~ fro~ the ~agnetostrictive assembly 350 can thuc ~e u~ed directly to pulse the enety~ ~ource 54 (see F$g. 2) such a~
an LED, and the re~ote control unit 34 can ' L6~L the p~lcec and dete~ i n~ the time delay ~eL~ the received elec~ rLic pulses, all without the need for special ti~ing log~c ci~cuits in the ~ensor el~_L,~nic~, if so desired. In other ~ords, t~e output ~ignal p~lfic5 from the ~ -Lostrictive asse~bly 350 inherently contain, in their time r',~ in spacing~ the dat~ for determining the float 304 relative position and hence the fluid level, quantity, volu~e, ~ass and so forth. These pul~e~ can thu~ be coupled to an LED to pulse the LED in a ~i~ila~ manner for detect$on by the re~ote unit.

27 21~2880 A refQ~_..C_ ele-8r~ ie pul~e can be p~o~o~ c~ ul~er~t ~ith the ~rP~ tion of th- curl~L pul~e to the ~veguide if so de6ired. In thi6 arrange~ent, the ti~e del~y ~ e.. receipt of the ref~ e ele_L,r ~ ic pulse ~nd receipt of the el-~L~ pul~e t~at ~rr~ to the r~flected acous~ic ~ignal provide~ an in~ tion of the sen~o~ 352 length and thus could he u~ed a8 part of a 6~.a~ e~ification code.
With re~er. ~e to Fig~. 13A and 13B, the ~tick gauge 318 is an ~lo~Pted ~e~ber that ha~ a relatively flat ~tick-like body 1~ 3~0. The stlck is attached ~t one end to a ~ide of a spool 382.
The spool 382 carries a ferro~agnetic band 384 th~t is nagnetically ~d~t~led by the float magnet 306 ~hen the ~tick 318 i~ allo~ed to drop down fro~ it~ ~tored po~ition (when the dripstick a6se~b1y 308 i~ fully installed in tbe housing 302).
The spool 382 includes a tb~ou~ bore 386 that is laterally of~set fro~ the sti~k 380 ter~inus on the spool. The bore i8 a~p~y~iately sizcd to sli~ably receive the upper di~tal end 356 of the magneto~tricti~e 8ensor 350. The lateral offset ~et~
the bore 386 and the stiok 380 per~it~ the sticX 3R0 to lie on or closely adjacen~ the flat surface 332 of the D-~be 330 (~ig.
llA), As shown in Fig. 10, the free end 3~8 of the ~tick gauge extend~ to the lower end of the D-tube as~embly 316, and for co~venience can slide into a small gap in the cup 336. As further ill~strated in Fig. 10, the stic~ body 380 is pro~ided wi~h a serie6 of ~arkings or gradations 378 that provide a visual indication of the float le~el inside the container. The markings can be read, for exa~ple, with e~ec~ to the container ~dge ~here the stick exits the container, or alternatively for example, vith l~a~ec~ to a reference mark placed on the D-tube 330.
With ref~er.~e to Fig. 14, the cap as~e~bly 310 include~ ~
shallo~ cup ex~pns~nn 322 in Y~ich is ~ o~1 a photocell array 3Z4 and an LED 326. Th~ illed in the art will ~re~iate ~hat, al~-o~ in this exemplary : ` 'i r~t the array 324 and LED

2~ 2152880 326 are ~ir-D~,e' in the cap ac5e~bly 310, thi~ is a matter of co,..~ r~o. me optical el~ t~ could be located in other areas, of a w mg or aircraft for exa~ple, ns de~ired for a particular ~rFIication- P~lLh_~more, the photocell array 324 need not be ~i6pQ~d at the sa~e location a8 ~he LED. The energization of the ~ensu~ ~50 ele~LLu--ic~ could alternati~ely be acco~plirh~', for exa~ple, ~rom anuL~_~ location, or even ~ro~
a~ on-board supply (without an opti CA1 cv ~ Ler as de~cribed herein). Tyrically, al2L~h not n~ o~ily, the LED 326 (or other transmi~ting device as de~ired) will be ~-cro~e~ near the sensor 350 ou2~uL to reduce lo-~s of eignal sL~el.yLh and noi~e.
~ he photocell array 324 i-~ one example of a detector 44 (Fig. 2) tbat detects elec~ . ~rDtic el~ received from the remote ~u~L~ul unit 34 and ~u..~ L~ it into useful electrical en~rgy that i~ u~ed to enerqize the ~agnetostrictive sensor 350 and associated cle~ru~lics~ as well a~ the data e~ circuits ~ssociated with the sensor cG~LLol circuit 40 a~ previously de~cribed herein. The L~D 326 can be used in this case as the electromagnetic energy ~ource 54 to transnit data back to the re~ote control hand-held unit 34. As shown in Fig. 10, these photosensitive devices are positioned outside the container 80 that a re~ote unit can trans~it and receive ele_L~ etic energy su~h a~ from the ground (in application~ 8uch as ~ing mounted fuel tanks, ~or example). Wires 3~0 ~on~_L t~e photocell array 32q and the T-~n to the el~LL~-,ics on the circuit board 360 located inside t~e D-tube 330. The~e wires can be routed through a bore 39~ in the cap a~se~bly and the axial bore in the s~ivel ball 333 previously de~cribed herein.
With reference to Fig. 15, we show an electrical ~che~atic diagram of a ~uitable tr~c~i~er cu..L~ol circuit 400 for the ~agnetostrictive sensor 350. ~hose ~ e~ in the art ~ill re~dily a~le~iate that thi~ circuit i~ but one example o~ ~any types of control circuit~ that can be ufied, the design of ~hich will be application bpecific. The circuit of F$g. 15 can be co~ r.iently i~ple~ented with the overall data tran~fer circuits 29 215~880 Yith the re~ote c~.l~ ol unit 34 earlier de~cri~ed herein if so de6ired.
~ n ~ig. 15, the photocell array 324 p~O~lC~ electrical ~e~ in ~e~ to detecting ele~ ic c~Lyy received fro~ the remote unit 34 ~or alternatively from a~blent light, for exa~ple, vhen ~nah!e~ by a 6igna1 fro~ the re~ote unit). Thi~
electrical E.~ $s ~tored $n c~pa~;tor C3 for ~upply to ~he el~c~ cc over a positive rail 401 (Y~UPP1Y) and a n~gative rail 403. A co~ ional multivibrator 402 ~hen energiz~d periodic~lly pulsec an FET switch Q2 Dn. Those ~ e~ in the art will readily a~e~ia~e that more intricate ~ ul circuits can be i~pl~ l~ted, alt~ough in so~e application~ power di~sipation ~ay be a de~;~n ~actor ~ on ho~ ~uc~
electrical e..e~gy i~ stored (alternatively as de~cribed herein 15 the electri~al supply can be provided thlU!~ 'O~ th~
inte~ ~dtion period).
The waveguide 364 is e~ cLed electrically in series ~ith the LED 326 ~Dl) and the po6itive supply rail, as well a6 in 6erie~ with the FET ~witch Q2 and the negative supply rail.
Thus, when the switch Q2 is p~lsed on, a ~4L~ -- pulse is applied to the ~aveguide and a reference light pul~e i6 p? ~.7..c~.1 by the LED 326 ~hic~ can be detected by the remote ~u,.L~l unit 34.
The magneto~trictive sensor receiver unit 354 detect~ the acoustic p~ s and produce~ electr$cal pulse6 that cu~ n~
to anplitude and duration of t~e direct and reflected aco~tic ~ignals. The~e electrical signal~ are a~plified by a conventional a~plifier circuit 404 and dete~ted by a comparator circuit 406. The comparator output is used to pul~e a eQoo~A
switch Q1 at each time an acoustic cignal $~ detected above a detection threshold level by the conparator c$rcuit 406. Thi6 e5 p~ from the LED 326 that can be detected by the remote unit 34 corre~po~i n~ in time to the acou~tic pulse detections.
The remote unit 34 can be provided ~ith a~op-iate tining circuits for deter~ining the time peribds between the detected LED p~l6es and hence therefron c~ ate the relati~e pos$tion of the floa~ 304. Fro~ the calculated float po~ition, the remote unit 34 el~ o..ics can further deter~ine the fluld quantity from look-up tables stored in :1~ that relate ~uel height mea~ureoents at one or nore ~loat 6ensors to voluoe, as descrlbe~
here~n~fore. Alt~rnati~ely, Yhen the ~agn_LG~ tive ~en~or i~ interrogated by on-board circuitry (~uch as an aircraft f~el ~ ent 6yste~), the a~pli~i~d r~ can be traneritted to the fuel ~rJ ment ~ystem by hard~ired c~--"~c~ions in~lll~lng electrical c~ ors or optic fiber~" ~or exa~ple, for further o~es~ing to deter~ine fuel height and quantity.
A6 another alternative, the sen~or el~L~o~.ic~ o~ Fig. 15 - could ~urther include logic circuits rOr deter~inin~ the float po~ition ba~ed on the time delay kat~ee., the received acoustic p~aes~ and ~n~ this data for vireless tran~nission to the r~mote unit 34. Other alternative ~ Ls o~ the cu..~
ele~401-ic~ and 6ignal ~voes~i~g functions ~ill be apparent to tho~e skilled in ~he art, Yith the . ~ i~entS of Fig~. 2 a~d 15 being inte~ded to be exe~plary in nature and not otherwi~e limiting.
In the exemplary e~oAi - t herein, ~ahual rea~ing of the - stick gauge 313 ~an be carried out as f~llo~s. m~ cap a~6embly 310 i~ ~.6cr~J~d fro~ the hDusing or container mount$ng ~tructure, and the a~seib~y 308 i~ either p-ll-~ do~n or alloved to drop dovn until its upper end engages the ~ounting 6~ u~ æ
via retainer 35B to ~le~"L the entire agg- ~ly fro~ dropping out of the ho~ g 302. As the drip~tick asse~bly 308 i~ lo_ ~ed, the ~tick gauge 31B al~o drops until the fe,rl ~etic band on the spool 382 aligns and is eng7Jnd by the ~agnetic flux o~ the float ~agnet 306. When the spool ls nagnetically c~tul~d, the ~tick gauge 318 di~. ~79~ ro~ free e~d 356 of the ~agneto~trictive ~ensor 350 ~hich continueæ to drop ~ntil retainer 35B e~ . AS the æen~or 350 is 1~ , the fre~ end 388 of the ~tic~ gauge also Rl id-- out of t~e c~p 336 of the D-tube a~æ~ ~ly 330, and ~ ~6 free of the __.~o~ 350 ~o that th~

-n-la,~ rea~ing thereof can then be taken. Due to clo~e tole~anm~- bet~_~n t~e D-tube and t~e hou~in~ 30Z, the ~tick 318 Yill tend to ~tay adja~ent the D-tube during a re~in~ but ~ho~ not hang-up and can be -n~l ly ~nved or rsadjusted in height until the operator feel~ the ~pool engage6 the float ~agnet 306. After the te~ i6 taken, t~e D-tube aF~er~ly can be ~ ac~ up into the ho~fi1~g 302. As tho ~-tube~
reLn~erted, the free en~ 356 of the ~ L~ 1ctlve ~n~ 350 will ~lide back into the bore 3~6 in the cpool 382 and the etick ~ill l~e,~-J-ge with the cUp 336, and the stick gau~e ~ill ~o~e inteqrally with the D-tube baok up into the hou~ing 302. The ~tick gauge ~ can al~o be taken with the a~eV ~ly 308 - co~pletely ~ d from the hou~ing 302 if ~o de6ired.
While the invent$on ha~ been sho~n and described ~ith re~e_~ to specific e~bodLments thereof, thi~ i~ for the ~r~c of illuatration rat~er than li~ltation, and other ~ariation~ and modif icat$0n8 of the specific embodiment~ herein sho~n ~nd described ~ill be apparent to thoae ~killed in the art ~ithin the intended spirit and ~cope of the invention as aet forth in the 20 a~Fe. ~_a claima.

Claims (10)

1. Apparatus for detecting fluid level in a container, comprising: a housing adapted to be disposed in the container; a float with an associated magnetic element, the float position corresponding to fluid level in the container; a magnetostrictive sensor disposed inside the housing; and a stick gauge disposed inside the housing;
the magnetostrictive sensor and the stick gauge each being operable with the float to determine the position thereof.

2. The apparatus of claim 1 wherein the container includes an opening through which the magnetostrictive sensor and the stick gauge can be at least partially withdrawn from the container without loss of fluid in the container.

3. The apparatus of claim 2 wherein the stick gauge comprises a ferromagnetic element that is captured by the float magnetic element when the stick is partially withdrawn from the container, the stick carrying indicia thereon for visual determination of fluid level in the container.

4. The apparatus of claim 2 wherein the magnetostrictive sensor comprises an outer tube that is slidable within the housing and which helps guide the stick gauge within the housing.

5. The apparatus of claim 3 wherein the stick gauge includes a spool at one end thereof that engages with one end of the magnetostrictive sensor when both are inserted inside the housing; the spool carrying the ferromagnetic element so that the spool is captured by the float magnetic element and disengages from the magnetostrictive sensor when the sensor is at least partially withdrawn from thehousing.

6. The apparatus of claim 1 further comprising means for wireless interrogation of the magnetostrictive sensor.

7. The apparatus of claim 6 wherein the wireless means comprises a transceiver coupled to the magnetostrictive sensor, and a remote unit that transmits and receives electromagnetic energy therewith.

8. The apparatus of claim 7 wherein the magnetostrictive sensor is disposed inside a mounting tube; the mounting tube having a mechanism that releasably engages a mounting flange on the container so that the sensor can be at least partially withdrawn from the container.

9. The apparatus of claim 8 wherein the transceiver comprises means for detecting electromagnetic energy from the remote unit, means for transmitting electromagnetic energy to the remote unit, and circuit means for controlling thedetecting means and the transmitting means.

10. The apparatus of claim 9 wherein the transmitting means and detecting means are retained in the tube mechanism, and the circuit means is disposed on acircuit board disposed inside the sensor mounting tube.
1 1. The apparatus of claim 10 wherein the detecting means and transmitting means comprises photoelectric devices.
12. The apparatus of claim 11 wherein the photoelectric devices operate in the infrared spectrum.
13. The apparatus of claim 12 wherein the remote unit is a hand held device that can be used to interrogate the magnetostrictive sensor from ground level.
14. The apparatus of claim 1 further comprising a circuit for applying current pulses to the sensor and processing output signals from the sensor, said circuit being disposed in the housing with the sensor and stick gauge.
15. The apparatus of claim 14 wherein the magnetostrictive sensor is disposed inside an elongated mounting tube; and further wherein the circuit comprises a number of components disposed on an elongated circuit board disposed inside the mounting tube.
16. An integral fluid level detection apparatus adapted to be disposed in a housing that is disposed in a fluid tank and having a magnetic float associated therewith such that the position of the float corresponds to the fluid level, the apparatus comprising: a magnetostrictive sensor that can be installed in the housing through an opening in the tank, and a stick gauge that can be installed in the housing with the magnetostrictive sensor; the sensor and stick gauge each being operable to determine the float position.
17. The apparatus of claim 16 wherein the magnetostrictive sensor is slidable inside the housing and can be at least partially withdrawn therefrom to permit the stick gauge to be manually operated.
18. The apparatus of claim 16 wherein the magnetostrictive sensor comprises a wireless transceiver that can be interrogated by a remote hand held unit.
19. The apparatus of claim 18 wherein the transceiver comprises means for converting detected electromagnetic energy received from the remote unit into electrical energy for energizing the sensor and transceiver.
20. The apparatus of claim 16 wherein the container is an aircraft fuel tank.
21. The apparatus of claim 20 wherein the magnetostrictive sensor can be interrogated by fuel gauging circuits on the aircraft.
22. The apparatus of claim 20 further comprising a remote hand held unit for wireless interrogation of the sensor.
23. An integral fluid level detection apparatus adapted to be disposed in a housing installed in a fluid tank and having a magnetic float associated therewith such that the position of the float corresponds to the fluid level, the apparatus comprising:
an electrically readable sensor assembly that can be installed in the housing through an opening in the tank, and a stick gauge that can be installed in the housing with the sensor; the sensor and stick gauge each being operable to determine the float position .
24. The apparatus of claim 23 wherein the sensor assembly comprises a magnetostrictive sensor and the stick gauge comprises a manually operated gauge that provides visual fluid level detection.

25. In combination, a magnetostrictive sensor for determining position of a movable element, and means for wireless interrogation of the sensor.
26. The combination of claim 25 wherein said interrogation means comprises a circuit disposed near the sensor, and a transceiver disposed at a remote location that transmits and receives electromagnetic energy through air with the circuit.27. The combination of claim 26 wherein the magnetostrictive sensor is disposed in an elongated tube that is adapted to be slidably installed in a housing inside a fluid tank for determining the position of a float guided by the housing.
28. The combination of claim 27 wherein the circuit is disposed on an elongated circuit board inside the elongated tube with the magnetostrictive sensor.
29. The combination of claim 26 wherein the sensor produces output pulses that correspond in time to the position of the element, and the circuit comprises means for transmitting electromagnetic energy pulses to the transceiver in response to said sensor pulses.
30. The combination of claim 29 wherein said transmitting means comprises an LED that emits light pulses in response to the sensor output pulses.
31. The combination of claim 26 wherein the sensor is energized by electromagnetic energy received from the transceiver.
32. A method for determining fluid level in a container comprising the steps of:
a. determining the position of a float that floats at the fluid surface using a magnetostrictive sensor;
b. producing pulses from the sensor that correspond in time to the float position; and c. using the sensor pulses to pulse a device that transmits electromagnetic energy to a detector unit remote from the sensor.

33. The method of claim 32 further comprising the step of using electromagnetic energy transmitted by the remote detector unit to energize the sensor.
34. The method of claim 32 wherein the device is an LED that is pulsed in response to the pulses from the sensor, and transmits light through air to the detector unit.