Note: Descriptions are shown in the official language in which they were submitted.
l '?~
-1 ¦ B~ Q~ n~ L ~Y~
2 ¦ There are many place~ where ins~all~tion of ice accumulation
3 ¦ monito~6 could be advan~geou~O ~y way of example:
4 ¦ At a1rports~ operationR personnel could use 1nformation fzom
5 ¦ ice accumulatlon monltor6 to ~lert ~hem to un6afe operatlng
6 ¦ condltions cau3ed by lce ac¢umulation on runway~;
7 ¦ On highways~ in~ormation ~rom lce accumulation monito~s
8 ¦ could actuate 8ign~ to alert motori~t6 of dangProus icings, and
9 ¦ inormation rom ice accumulation monitor~ could inform highway
10 ¦ department per~onnel a~ to where tbe highway~ nePd sanding,
11 ¦ salting, and/or ice removal;
12 ¦ On buildings, ice accumulat~on on roof~ could be monltored
13 ¦ to indlcate when ice r~moval wa needed~
14 ¦ On aircraf~ wings and o~her aircraft s~rface~, ice
15 ¦ accumulation monitors woul~ provide informat~on to warn aircraft
16 ¦ operators of unsafe ice buildups~ and
17 ¦ On radomes, ice accumula~ion monitor6 would activate deicing
~8 ¦ equipment when ice accumulation is great enough to interfere with
~9 ¦ reliabl~ operation of the enclosed antennas, or. warn per~onnel
2~ ¦ when deicing was necessaryO
21 ¦ ïn re~erenc~ to previously disclosed equipment used ~o
22 measure ice accumulations, there has been:
23 Equipment :~or me~suring ice accumulation by analyzlng
c~any2~ tn ~recduency of an oscillating element as lce accumulate~
2~ on the elementO ~he ~l~men~ generally protrudes iErom a ~ur~ace~
1 ,~`
"Jj~
. . ,
: ;. . ~ , ,
- . ~
.
~,
-1 ¦ 50 the element i5 susreptible to traff ic da~D2ge when ~nstalled in
~ ¦ a roadways Al~o becau~e the element protrude~ rom the surfa~e
3 b~ing monl ored, $cing conditions on the element may differ rom
4 icing conditions on the ~urace. In anc~ther embodiment of æuch
5 an osc~llating element, a protective cap~ flat for roadway~,
6 accumulate~ d ir~ ~o that this element i~ not rel:lable because it
7 does not dlstin~ui~h between dir'c accumulation and ice
8 accumulat ion;
9 EquiplDent or measuring ice accumula~ion by analyz~ng
changes in the obstruction of light by the formation of ice, witb
the light channel portions protruding above the ~urface and
12 thereby being subjç~ct to damage by traffic and inacc:uracies
associated with protrudlng elementsi
14 Equipment for meaF~uring ice accumulation by analyzing
15 changes in the pressure drop across an orifice9 being caused by
16 the formation of ice, with orif ice por~ions protruding above the
17 surface and thereby being subject o damage by traffic and to
18 inaccuracies as~ociated with protruding elements~
19 ~quipment using internal reflections to detect ice formatior
on a ~urface, a~ set fortb in U.S. ~aten~ 2~359,78~. HoweYe~a
21 this equipment does not measl re ~he amoun~ o~ ice accumulated)
22 and does not indicate methods for compensatlrlg for interferences
23 ~rom chang~s in ambient light o~ ~or di~tinguishing the pre~ent::e
24 o~ dir~ or mud~ and
Equipment using internal reflecl:ions to d~tect ~ce formation
' .
--
~ 3~3
~ 1 on a surface,1 as set forth in U.S. Pa~ent 3,540~02~. ~owever,
2 this equ ipmen~ u~es a se~ ies of hea'cin~3 steps followed by removal
3 of the melted ice, to indlca~e ice formationO Because the~e
4 meltlng steps interfere with ice accumulations, continuou~
5 mea6uremerlt~ of ic~ accumulatlon are not pra¢~ical with ~his
6 e qu ipmen t ,,
7 The prior equipment is believed not to have been adequate in
~ measurlng accumulationG of lce and espec:ially inadequate for
9 measur ing the continuisus accumulation of cracked or otherwise
f lawed ice .
~1
12 5~:~}1~
13 This ic:e accumulation monitor ~dequately mea~ure~ ~.he
14 accumulation o ice, includ~ng accumulations o cracked, or
o~herwise ~lawed ice, as i~ ocs::urs on any ~urface, such as
16 roadwaysD airport runways, sidPwalks9 radomes, aircraf~ sur~acesJ
17 and the roof~ o buildings. The ic~ accumulation mon tor
18 inc:lude~ a prism which is transparent to radiation emitted by an
19 emitt~rg which prism ha~ one surface exposed to~ice accumulation,
thls surace being flush with, and cont nuously in the same plane
21 as r the surface be~ng monitored; an emitter o~ pul~ed
22 electromagnetic radiatioll orlerl~ed so ~hat a~ ~che exposed prism
23 surface the emitted radiatiorl is ~otally rel~ected within the
2~ prism when the exposed sur~ace ~s ~are, but the emitted radiation
~s only parit{~lly reflected within the pri~m w}~en ice cover~ the
__ ._ _ . . . ... . ..
. .
.
'
~ ' :
, ~ ~
~ ~-
t 3
1 exposed prism surf~ce; and ~wo radiation detectors to measure the
~ lntensities of the reflected radiation, and located with one
3 detector clo~er to the e~posed surface than the other detectorO
d~ A temperatur0 sensor, located ln the pr ism near the exposed
5 surface; i8 used to aid in distinguish:ing accumulations of ice
7 from accumulations of watera Preferably th~ expo~ed surface of
the prism is al80 a surface of a very hard transparent layer that
8 will not be ~cratched or otherwlse d2maged by traff ic or o9:h~r
9 abusive elements. To avoid nonl~near detector responses at the
10 relatively high radia ion levels that can result from ome
11 ambient ligh lng conditlorls, a bandpass filter, with its bandpass
12 wavelength centered near the dominant wavelength emitted by the
13 emitter, is located at a position in the prism that s:~au es the
14 amount of ambient radiation reaching the detector6 to be reducedO
15 The effect of ambient radiation lz then eliminated from the ice
16 accumulation measurements by subtracting the rad iation detector
17 responses when the emitter is in the off portion of its cycle
18 from the rad iation detectos responses when the emittPr is in he
19 on portion of its cycle.
20 ¦ When ice is not present on the exposed surface of the pxism"
21 ¦ the emitted radiation is cc>mplete}y reflected back into the prism
22 ¦ at the expo~ed prism surfacl3 and detected ~y the ~adiation
23 ¦ detectorsO ~he relative position~ of the d~Ptect~rs.i~ ~ucb that
24 ¦ the intenf;~ty of rad~ation detected by one de~ector is greater
2~; than detecteà by tbe other detector. When ~c:e ~tart~ to
.
.
~ 3~3
1 accumulate, some of the emitted radiation is transmitted into the
2 ice~ thereby reducing ~he amount of r~dia~ion reflected ak the
3 exposed surfac~ Tbis reduction in radiation reflec~ed at the
4 e~posed surface, combi~ed with the dif~erent path to the
detector~ by radiation re~lect~d at ~he ice-alr interface,
6 changes the radiation i~tenæitles detecSed by each det~ctorO
7 Through calibration, ~hese changed intensities are relat~d ~o ~he
8 amount of ice accumulated~ By this method, accumulation~ sf
9 cracked, or otherwise flawed, lce, as well a6 accumulation~ of
la pe~fect ice can be detected and measuredO
11 In callbra~ing this ice accumula~ion monitor, ~he dominan~
12 wavelength o~ tbe emitted radiation is selected ~o that ~he inde~
13 of refractlon of ice at ~his wavelength i~ practically ~he ~ame
14 as the index of refrac~ion of water at this wavelength~ ~ereby
allowing accumulations o~ water to be u~ed to determ~ne a
16 callbration ~urve for each radlation detector. Additional
17 calibrations are undertaken o the ~ea~ured intensities of the
18 reflected radiation will indicate when the e~posed surface of the
19 pr i8m i~ cover~d with dirt or mud and needs cleaning.
As so arranged D installed, and used, this ice accumulation
21 monitor adequately m~a~ures the accumulation of ice in all of it~
22 formationsO If dirt or mud appear, their presence is detected,
23 ao they may b~ removed and ~he measurement~ can he resumed~ The
24 meaaurements ~ay be tran~mitt~d to central observing instruments,
to nearby ~igns~ a~d to other place~ to warn inter sted observe~g
.~' ' ~ .
~ i3~L~
~ of tbe amount of ice accumulated on the monitored ~urface,.
4 The lce acc:umulat~on monitor i~ ~bown" in ~eference to a
preferred embodlment, in the drawings~ whereins
6 Figura 1 shows tbe reflectivity of bared and ice ~overed,,
7 fu6ed quartz 1nterfaces ~or unpolarized radiation orig:lnat~ng in
8 the fused quartz;
~ Figure 2 i~ a vi~3w of the ice accumulatlorl monitor in th~
10 pl2ne of a ~urface l:hat 15 ~eing monitored fo~ ice accumulat~on;
11 Figure 3 i8 a schematic sec~cion view of the il~e ac:cumulation
12 monitox pv8 itioned s~lth ~he exposed surfaoe ~f it~ transparent
13 prl~m flush withp and contiruou~ withr the surfac~ being
14 monltored or ice acc-lmu~ation" and $ndic:ating the location oiE an
15 emitter of pul~ed electromagnetic radiation, the locat~on~ of 'cwo
16 radia~cion detector~, the location of a len~ for collimating
17 radiation from the emltter, the location of a bandpas~ fill:er
18 positioned 1:o reduce the amount of ambient radiation reaching th
19 radiation detectors~ and a locatior; for a . empera~ure sen~or~
Figure 4 i8 a s hemat ~ diagram of an emitter drilveJc:ontrol
21 circuit ~or temperature-independen~ pul~;ed emis;lon from a laser
22 diode/photodiode package~
23 Figure 5 is a ~c~ema ic d~agram of an emi~'cer drive,~c:o2ltrol
2~ circuit ~hat u~;es a thermistor as a ¢ontrol element to obtain
25 temperature-ind~pend~n~ pul~ed emi~;ion frsm an emitter that doe~
___ _. . . . .. . . . .. .... . . .
.. , ~ . , ~ .. . .
- : ' ~
. .
9.~ 3
-1 not bave an in~egral means for monitoring eml~sion in ensity~
2 Figure 6 i6 a ~chematic: 6ection view, showlng an optlcal
3 fiber ~or transm~tt:lng emitted radiation from a remote emittez ~o
4 the prism~ and 6howing optical fibers for tran~mitting internally
reflected rad~ation to remote detectors~
6 Flgure 7A shows an alternative ~ rectangular prism c~o~
7 section, with the emiltter and de~ec:tor located within the prlsm;
8 Figure 7E~ shows an alterna'cive, ~riangular prism cro~s
9 ~ection, with the emikter~ and detector located on pri6m urfac:e~;
lo Figure 8 i~ a schematic sectiona~ view, imllar to figure 3,
11 but showing electr~cal connection6 to a cablLe connector ~ and the
12 prism in a container and cushi~>ned ~y an elastic material~
13 Figur~ 9 show~ a ~chematic c~rcuit diagram of a s:on~tant~
14 current 80urc~ driving a thermi~tor temperature ~en~or;
Fi~ure lû is a schemstlc sectional vlew" similar to igure
l~i 3, but showing an accumulation of ice on the surface bei~g
17 monitored and on the expo~ed surface of the transparent prism,
1~ and showing a path for emitted radiation that is reflec:ted from
19 the eacposed surface of the prism and a path for emitted radiaition
20 that is re~lected iErom the ice-air inter~ace of the accumulated
21 ice,
22 Figure ll shows rad iation detector responses to
23 accumulal:lons of p~riEect ice or of water, and ~hows ranges of
~ respon~e& to an accumulation o~ flawed ice;
Figure 12 shows an interpretat~on of radiation detector
~ ~753~3
1 ¦ re6pon~e~ a~ bands of accumulations;
2 ¦ Flgure 13 ~;hows detect~r responseE; corre~pondirlg to ps~ ble
3 ¦ accumulat$o~ of water ~ and
4 ¦ Figures 14a and 14b show logical steps involved in analyzing
5 ¦ data ~rom th~ radiation detectors to eliminate the effect of ambient
6 ¦ radiation, to discriminate against accumulation of water, to
8 ¦ discri~inate against deposits of soil ox o~ mud, to determine ice
9 ¦ accumulatiorls, and/or warn of dangerous ice accumulations.
'lU i ~_~ _
l To provlde a backgro~.and for understanding ~he equipment and
12 ¦ opera~ion de~cribed, opticE; concepts that relate to thi~ lce
13 accumulation monitor are described ir to then the equipm~n~ and
i~ operatiLon are describeda
~hen a light wave (electromagnetic radiation~ i~ incident a'c
16 an interface between two tran~;parent ~aterials with different
1~7 indexe~ of refraction" the wave ~;plits into t~o waves; a
18 transmitted wave which proceed~ into ~he sec~nd materi3.1f and a
19 I reflect~d wave which i~ propayated bac:k in'co-~he fir. t matelials,
20 ¦ Snell'6 Law relates th~ or~en ation of khe r~diation ~chat i~
21 ¦ transmi~ed into ~he second material ~o the orientation o the
22 ¦ inc iden t r ad iat ion .,
23 I The proportion of the inciden. energy that is reflected at
I the interface 15 characterized by the reflectiv~ty (t~e energy
æs I a~3socia~eed w~th ~he reflected wave divided by ~he en~rgy
I 8
. ' , . . .
.
'
.
.
` 1 as~ocia~ed wlth the incident wave) which can be calculated froin
~ Fre~nel's formulas~, and which depends on the angle of incidence,
3 ,0~, ~the angle that ~he incident wave alakes wlth the normal to
d~ the interface~ ~ and which also depend~ on the ra'cio oiE the
inde2~e~ o refrac~loll of 'che ma~er ial~ on either ~;ide s;~f th~
6 interface. A xeflectivl~y of one indic:ate~ total reflec'c~on~,
7 Figure 1 shows the reflectivi~y of bare 12 and ice-cs~7ered
8 13 fused quartz interface~ iEor unpolar:Lzed radiatls~n originatlng
in the fused sIuartz. For lncident angles greater than a critical
angle7 ~c~ described by
11 0c ~ (n~nl~ ~ n2~
12 where nl i~ the inde~ of refrac:tion of the material ln which the
13 radlation originate~ and n2 is the lndea~ of refrac~ion o~ the
14 ma erial on the other 8ide of the interface~ the reflectiYity iB
one and the incidlent radiation is totally reflected. For
16 inc~dent angles less than the critical angle, the reflectivity ~
17 less than one, 80 some xadiation i5 transmi~ted acro~ the
18 interface into the material on the other slde of the lnterface.
19 The critical angle for bare fu~ed quartz is 43, and for ice-
covered ~u~ed quaxtz, the cri~ical angle is 64. Therefore~ when
21 ~ce cover~ a fu~d quar~z 8urface and radiation is incident at
22 the inte~face at an angle le~ than 64~ only part o~ tbe
23 incident rad~tion will be reflected~ the balance will be
2~ ~c ansmitted lnto the icea In ad~ition, ~nell'~ Law, ~ombined
with ~quation 1~ show~ that the radia~ion that i~ tran~mi~t d
I ~ ~
I ~ 3~3
~ into the ice will be totally reflec~ed a~ 'che ~ubsequant ice-air
2 interface if the radiatlon inc~dent at the fused quartz interface
3 is incident a~c an angle greater than the critical angle for the
4 bare fused quartz interface ~43) 9 and the fu~ed guartz-air and
S ice-air interfaces are parallel. Therefore,, ~adiation that i8
6 ~nc ident at an ice covered used quartz interfac:e at incident
7 angles between 43 and 64 will be parkially reflected ait tbe
8 interface and part~ally tran~mitted into the ice~ with that I?art
that i~ transmitted lnto the ice being totally reflected at the
10 ~ubsequent ice-air interface.
11 In figure 2~ th expo~ed surface 14 of the prlsm 17 of an
12 ice accumulation monitor 15 that use~ these optics conc~pts is
13 shown surrounded by a surac:e 16 that i6 to be monitored for lce
14 accumulationO E'igure 3 show~ a cross s~ction of the pri~m 17
15 . with a rad lation emitter 18, and a detector lg comp~l~ed of
16 separate radiation detectors 20 and 21, arrangad to u~e these
17 optics concepts to measure ice accumulation on the surface 160
1~ ~h~L~
19 In the preferl:ed embodimen~, the emi~te~ 18 is a
20 ¦ commercially ava~ lable la~er diode/photodlo~e package in which
21 ¦ the p~otodiode monltors ~he emission inten~ity o~ the lase~
22 ¦ diode, 60 that outpu~ from ~h~ photodiode can be used as feedbacllc
23 ¦ irl an electronic circuit to laaintain ~che la~er diode emis~ion
intensi~cy constant regardles~ o~ tempF~ratureO Emitter opera~ion
is also pulsed, so that the e~fect~ of cbange. in ambient
~O
' ' " ' '
~7~3~
1 rad~ation can be elimlnated from ice accumulation monitor
2 operation 0 By way of example, f igure 4 6hows a method for
3 electronically controlling ~he emltter 13 to obtain Pmperatllre-
4 independent emi~s~on intan~lty 30, and to obtain pulsed
5 operation,. 0UtPU~ from the photodiode 31 i~ the laser
6 d iode/pho~od iode pac:kage i8 used as ~eedback to cont~ol an
7 operational amplifier circul~ 32~ which supplies khe laser diode
8 drive current,. Pul~ed em~tter operation ls obtained by using a
9 pulse generator circui~: 34, based on a timer integrated circuit~
10 ts~ provide a ~quare wave input 35 to the operational ampll ier
circuit 3~ and to the amplifier section 336.
12 Alternatively~, ~n emitter such as a laser dlode or a light
13 emttt~ng diode ~LED) that does not contain an integral emission
14 moniltor can be u~ed with feedback from a temperature sensor 22 to
15 ob~air~ t~mperature~ dependent emis6~0n., Temperature sensor~
16 usable for this purpose include thermocouples, resistance
17 temperature de~ec~ors (P~lrDs) ~ solid state temperature devices~
18 and thermistor~; 9 By way of example, f igure 5 ~hows a method for
19 elec:tronically controlling opera~ion of a LE~ emitter 36 to
20 obtain a corlstant emisslon iIlten~ity 30 regardless of teDIperatu~e
21 and tD obtain pulsed emissions., ~n operational amplifier c:ircuit
22 37 dri~eR an amplifier section 32~, which supplies the I-ED drive
23 curren. Temperature depen~len~ feedback to the op~rat~onal
24 ampl;f ier ts provided by a thermis~oE 22 so tha~ ~he outpu~ o~
25 the operational ampli~ier changes to offset changes in emis&is:~
11
. _ _ . . _ . _ .. , .. . .. . .. _ _ _
.
- ~
~Z~531:~
1 ¦ lntensi~ty tha~ would re~ul~ from temperature change~. Output
2 ¦ from the operational amplif ~er i~ proportional to the thermi~tor
3 ¦ resl~tance, which ls proportional to temperature, ~o me~urement
4 ¦ s~f ~che operatlonal amplif ier OU~pll~ voltage, TEMP O ~180 provide~
5 ¦ a means for mea~uring the ~emperature, which will be uæ~d in
6 di~tingui~hlng lce accumulation~ from accumulation6 s~f water,.
7 As ~hown in f igures 3 0 8, and lO O ~he emitter 18 i~ mounted
8 withln the prl~m 17 and oriented ~o 'chat when the em~tted
9 radlation reache~ the expo~ed ~urface 14, it i~ in~ident at an
angle greater than the critical angle for a bare e~po~ed surface,
:11 ~0cYbare' but le~s than the crltical angle for an ice-covered
12 exp o~ ed s u r f ace ~ 0c ~ ic e-c ove r ed c
13 Alterna~ively thi lce accumulation monitor will operate
14 effectlvely with the emit~er mounted on the ~Loplng prism ~urface
lS 26 and the emitted rad i ation d irected at the eYposed sur~ace 1~
16 60 that the radiation is incident at the e~posed ~urface 14 at an
17 angle greater than 0c~b~re but le~ than 0c~:~ce-covered' or thi
18 ice accumulation monitor will also operate effectively with the
19 emitter 18 e~erlor ~co the prism and the elsitted radia'cion
20 tran~mitted to the prism~, and directed a~c ~he expo~ied surface at
21 an incid~nt angle greater than 0c ~ba~e but le~s c ic:e
22 c~ve~ ed by an optlcal f iber 38, as shown in igure h . Therefore
23 it i~ under~tood that the efectivene~s o~ th~ ic2 accumulatlon
24 monitor i8 llOt limi1;ed tc> emit~er placement; within the prism.
In addit~on, thi~ ice accumulation moni~or 15 will al~o
. 12
.
.
~ 75;1: L3
1 ¦ operate a~ de~cribed hereaf~er under ~_
2 ¦ Q~ i$ the emitter i8 or iented to produce less than total
3 ¦ reflec:tlon at the bare ea~poaed ~urface- ~owev~r, in thi~
4 ¦ situation, reflect$on at the lc:e-air interface i~ leas than total
5 ¦ and operation ls le~ efiEective, ~o emitter s~rientation producing
6 ¦ total reflec~lon at ~he bare expo};ed ~urfacP 1B preferred~
7 ¦ A lens 23 i~ located in a cylindris:~al cavity 24, which abut
8 ¦ the emitter 18, to be effective in c:ol:l imating the radlat~on from
¦ the emitter . Some emitter~ have int~3gral ::olllmating optlc:s 80 a
10 ¦ separate collimating lens 23 would not be requlred for the6e
11 ¦ emltter~ O Elowever ~ rad iation em~tted by many emiJcters is no~
12 ¦ ~uff iciently collimatad to provide e~fective operation of the lce
13 ¦ accumula~ion monitor, ~o the collimating len~ is lndicated in
14 ¦ this preferred embodiment~.
15 I ~h~i~m
16 ¦ The pr ism 17 is tran~parent to rad iation emitt~d by the
17 ¦ emitter 18 and ~n ~he preferred embodiment the prism ~ection 3-3
18 ¦ has a trapezoidal shape as ~;hown in figure 3. Elowever~ aB lo~g
19 ¦ as the ori~ntation of the ~mltted radiation ~ith respect to the
20 ¦ exposed sur~ace 14 i~ such that significant reflection 0C:611r~; at
21 ¦ both he bare e~posed surface and at the ice-air interface of an
22 ice-covere;9 exposed surface~ ~his ice accumulation monitor will
23 opera~ce eiEfec~ively wi~b prisms havin~ other ~:ro~æ sectional
24 ~hapes, ~uch a~ the rectangular ~;hape ~hown ln f igure 7A and the
25 triangular ~hape shown in ~igure 7B. There~ore it is under~ood
.
.
~ 5;3~3
1 that the ef~c~ivene~ o ~hi~ ic:e accumulation monitor is not
2 limited to prisms having the trapezoidal shape ~uch as 6hown in
3 ~Eigure 3.
4 In the pr~erred embodimerlt th~ p;t:i8m i5 made of fu~ed
5 quartz, but thi~; ~ce accumulation monitor will also operate
6 e~fectively with a p~$~m made ~rom any oth~r optical quality
8 material which i~ . ran~parerlt to radiation from the emitter and
has an indeY of re~raction greater than the inde2~ of re~rac:tion
of ice. One embodiment of the preferred emitter emit~ a'c 8~0 nm.
10 For this emitter, such other mater ials include most optical
11 glasses, ~apphire, and ruby.
12 The longer 14 of the two parallel ~urfaces of the prism is
13 e:~po~ed to lce accumulation ~ and i~ arranged flush with the
14 surfac~ 16 which is to be monitored for Ice accumulation.
15 Because scratche s~n ~he e~po~ed surface 14 interf~re wi~h
16 effective operation of this ice accumulation monitor~ it ifi
17 preferable that the exposed ~urfa~e 14 also be the e~posed
18 ~urface b~ a hard transparent layer 28~ as ~hown in f~gure~ 3t 8,
19 and 10, which will not be ~c:ratched or o~herwise damaged by
20 traff ic or other abusive el~ments, and which al~;o has an inde~ o~
21 refrac~ion grea~er than the index o~ reîraction o~ ice. 5uitable
22 mater ial~ ~or he hard transparen~ layer include sapphiEe a~d
23 ruby. :tn addition, the operation o~ the ice ac:cumu}ation monitor
~!4 15, i~ not changed i~ ~he entire prl m 17 is made from the hard
mater i al; used preferably as the hard tran~parent layer 280
14
_ _, . _ _ _ . . . . , _ . . . . .
,' ~ . : '
.
.
.
.
~ ~7~3~3
¦ ~lowever~ bec:au~e the hard materi~ 3 are typ~ ally more expen&iv~
2 ¦ than the prism mater~al and are u~ually more difficult to
3 ¦ machine~ llmiting the hard m2'cerial to a layer 15 pxeferable tO
4 ¦ making the enti e prism from the hard mal~e~lalb
5 ¦ To further pro~ect against eatpo~;ed~surfac~ damage in
6 ¦ appl~catlo~ uch as roadway~ and runway~3, a~ ~hown ln figure 8,
¦ ~he entire pri~m 17 may be mounted in a contaln~r 41 a~d
8 ¦ cushis)ned by ar~ elast~c m~terial 42 that maintain~ it~ ela~ticlty
a~ low tempera~ure~ and ~ha~ deform~ ~o accommoda e agent~ that
10 mlght damage the exposed surfac~, then recover~ af'cer the
11 damagirlg agent pas e~O Suitable ela~tlc material~; for l;hi~
purpose include low tempera~ure silicon rubber~ eYpand d
13 polyethylene foams~ and clo~ed- cell~ high re~;illence polyur~3thane
14 f oam~ .
1~ Figure 8 also schema~ically show~ electrlcal connectlon6
16 from the laser diode/photodiode paclcage 18, a detector 19, and a
17 thermi~tor 22, ~o a cable connector 43, which cabl~ connecto~
18 connect3; ~h~e ice accumula~ ion moni~or components to an e~ter~al
19 cable 44 for c:o~ununication with the laser diode.:~photodlode drive
~0 control cirl::uit~ a ~eadout devic~ ~oz the detector, and a ~ceadout
21 dev~ce for the thermistor .
23 In ~he pr :Eerre~ embodiment ~h~ sloplng 6i~e ~6 o ~he pri~m
is angled ~o th~t radiation emitted perpendicular ~o this side i8
24 incident at the expo~ed sur~ace 14 at an lllcident angle greater
thar~ a~e but le~æ than 0c ~ ic:e -coYered ~ ~hi~ O
' ~ ~
~' ' ' '
. `
: -
1 the ~loplng s:ide facilitate~ mounting the emitter for effective
2 operation o~ thl6 ice accumulation monitor~ The other zloping
3 side 27 of ~he prl~m i~ angled ~o that radlatiorl re~lected frvm
dy 'che bare e~:po~ed surace inter~ect~ thls ~ p~ng ~ide
perpendiclllarly., Thi~ orlentation o~ the other ~loping 6ide
6 facilitates mountlng the detector 19 for ef~ective operation,,
8 A photodetector l9s c:omprised vf two separ~te radiat~on
~ detector~ 20 and 21~ i~ positioned within the prism 17, opposite
f~om the emitter 18, and oriented ~o d~tect internally reflected
11 radiationO Alternatively~ the operation of thi6 ice accumulation
12 monitor i8 not chanl3ed ~y tbe use of two, separate, radiatioTI
13 detector~ whic:h are not housed in a ~ingle unlt. In addltion,
14 operation of thi~ lce accumulation monitor i8 not changed by
positlonlng the photodetects)r on the ~loping prism surface 27t 03:
16 by transmitting the reflected rad~ation by optical fiber~ 39 to
17 e:Kternal photodetectors 40, as shown in f igure 6 .
18 A bandpa~s ~ilter 25 ~ with its bandpas~; waYelength centered
19 near the em~tter ~s dom~nant wavelens~th tran~mits r~flected
radi~tion from the emi~ter, bu~` 8i9ni~Ei.oantly redures ~he amount
21 of ambient radiation reachir~g the rad1ation detec:tors 20 and 21~
22 so that possible nonlin~ar radiation detertor ' responses at very
23 high radiLa ion l~vel~ do not occur. The e~ect of ambient
~!4 radiatiorl ~B then ~liminated by pul~ing tbe emitter 18 and
subtr~ctill~ detector respons~ obtained while lthe emitter i8 o~i~
16
.
,.
.
~ '
~753~3
1 from res1pon~es obtained while the emltter i~ on.
2 f_~
3 A ~emperature sensor 22, preferably located near the e:spo. ed
4 ~urface 14, i6 U ed I as di~cufi~ed hereafter under
5 ~_t_ D irl conjunctlon with response6
6 ~rom the two radiation det2ators to dl~tingui h betw~en
8 acs:umulation~ of wat~r and accumulation~ of ice. Tempera~ure
sensor~ usable ~or this purpose inr:Lude t~ermocouples, R~Ds,
solld ~ta~e temperature devices, and thermistor~. By way of
10 example, figure 9 shows a circuit diagram of a con~tant current
11 source driving a thermi~tor for use a~ a ~emperatllre sensor . The
12 6ame type of ~lrcuit 18 also applicable to RT3~o Alkernat~Lvelyt
î3 a bridge oircuit mea6uring the resistance of the thermi&tor or
14 RTD, or other resistance-measurlng circuits fam:lllar ~:o ~hose
15 skilled in ~3lec ronic~ could be used to determine temperature
16 with a thermistor or an RTD . Standard voltage measuring
17 technigue~ could be used to determlne temperatures from volt~ge
18 measureme2lt~ s)n thermocouples or sol:ld 6tate devtces.
19 As dlscu~sed previously ir~ ~he section ~h~m~0 the
20 temp~rature ~en60r 22 also may be used a~ a con~rsl element ~or
21 temperature sensitive emit'Lers that do not have an integr~l mean~;
22 ~or maintaining ~emperature independent emis8ion in'cen6iti ~0 I~
;3 t.he temperature 81~n~ 1r i~; al80 u~ed a~; ~ control element, the
24 ~emperature sensor is located 80 that it i~ near both the emitt~
. and ~he exposed ~ur~ace,9
h~
_ __ _, __ ..... . . , . ~. __ .. ...
, ' . ' ,'. ' - ' , ' ': , '
'~ ' ' ' - ' ~ ~ '
. . . .
.
' ~ ' ' '
~ ~7~ 3
2 ¦ AE; shown in f igure 10, when the ice acc:umulation monitor 15
3 ¦ i~ operated, a collima~ed beam of radiation 45 from th~ emitter
4 ¦ 18 ln~ers2cts the expo~ed surface 14 a~d ~L~ totally reflected 46
5 ¦ $f the e~po~ed ~urface is baIeq For clari. y i,n figure 10, beam~
6 ¦ o~ radiation are shown a~ respective rays 45~ 46, and 47. The
7 ¦ raaiation intensities d~tected by rad~ation detectors 20 and 21~
8 ¦ which are ~eparate section~ of photodetector 19r differ because
~ ¦ of the diferent positions, of 1;he~e radia~ion detectors 2û and ~1
îl) ¦ relative to the reflected rad~ation 46. A~ ic:e 48 accumulates on
11 ¦ the e~poaed ~urface 14y part of the emitted radlatiorl i~
12 ¦ tarn~mitlted ~nto the ice ~8~ and ~ubsequently reflected 47 at the
~3 ¦ ice-air lnterface 49, tbereby ~hiting tbe average effect of th~
14 ¦ re~lected radiation 46 and 47 towards the center of radlatio2l
15 ¦ de~es:tor 20, and ~lmultaneously ~ ting the ave~age e~fect of
16 ¦ the reflec ed radiation 46 and 47 from radiation de~ector 20
17 towards radlat;ion detector 210 Continued accumulation eventually
18 causes the aver~ge effec:t of the re~lected radia-ion to ~hift
19 pass radia~ion detector 2û ~o ~hat a maYimum oc:curs in the
20 re6po~se accumulation curve for radiatiorl de ec or 20.. The
21 response of rad~ation detector 21 i3 similar, but becau~e of the
22 d i~erent relative positions of radiation detectors 20 and 21,
23 the ma~imum for radiat~on de~ctor 21 occ:urs at 2 greater
24 accumulat~on tharl the maac :Imum ~or rad la~lon detes:~cor 20 . In
f igu~ 1, the cu rve 51 5 hows a typ1oal reiponBe-eocumulition
:
~ 3:~
-1 curve for radiation detecto.r 20" and the curve ~2 ~hows a typical
2 respon~e-accumulation curve for radiatlon det~r~tor 21.
3Calibration~ to obtain re~ponse -accumu~ ation ¢urve~ ~uch ~
a~51 and 52 are p~rformed by cal~brating radla'cion detector
5re~pon~e~ to kno~n accumulat i on~ of water ~. ~hifi iB poss~ble
6becau~e tbe inde:~ of refractiLon o:~ water i~ 1033 at the dominallt
7w~aveleng th emit~ed by the preferred eml'cter ~, and thi6 inde~s of
8refraction l~ practlcally the same a~ the index of refraction o~
lce,, 1.31~ at this wavelengtha
10Des$gn selections, ir~clu~ g t.he placemers'c of ~e 2mitter
1118, the placament of the radiation detec or~ 20 and 21, and lthe
12 l;rltensity of the emitted rad~atis:~n~ a~fect the 6hap~s6 and
13 locations of the calib~atlon c:l~rves with re~pect tv the re~pon~e-
14 as::cumulation coordinate~, ~o with differe~t de~ign ~election~;,
15 different calibration cur~e~ will be obtained. ~owe~RrJ
16 regardless of the ~hap~ and location~ of the c:allbration curve~i~
17 once the c:allbration c:urve~ have been s)b'ca~ned~ interpretat~on,
18 a~ de6cribed h~raafter, of radiation decector r~spon~e~ in te~m~
19 of the calibrat~on curve~ serve~ to d~termine ~he amoun of ise
20 accumulated 3
21I~ the ln~erf ace between iC2 and a~r 49 ~s un~verl t ~uch als
22 might be cau~ed by ~u~Eace ice needles form~d du~lng fre~zing or
23 by surface damage of the ice caused by tra~f ic:, or i.~ ~e ice ha~
24 in~ernal defec~s such as ~racture c:raclc6 caused by traffic, the
25 e~fec~ o~ the re~les~ed radia~on 47 will ~e diffu~ed and
19
.
'
,
. . . ; . ' .
' ' '
: ~ .
~7~3~3
1 orlented di~ferently from the effect of reflected radiatisn
2 tran~mi ted through perect ice with the ice-air interface
3 parallel to th~ e~posed ~urface 14 of the ice accumulat~on
4 monitor 150 Therefvre~ ~or any p~rticular accumulation of $ce,
the respon~e of aach radiation detector~ 20 or 21, will depend on
6 the severity of ~urface distortion and the severity o~ i~ternal
7 defects~ Thereore, response-accumulatlon cur~es ~uch as 51 and
8 52 repre~ent re~ponse~ to accumulations of per~ect lce? orO
because tbe index of refraction of wa~er i8 practically the ~ame
10 a~ the lndex of re~raction of ice at the dominant wavelength
emitted by the preferred emi~ter, accumulationc of wate~
12 ~owever~ becau~e o the po~sibility of ~urface di~tortion or
13 intgrnal defects, ~ny re~pon6e in a range between an upper l~mit
14 determined by curve~ such a~ Sl a~d 52t and a lower l$mit
15 determined ~y the response to a ~eYerely di~torted surface or a
16 severely damaged internal structure, w:l 11 be po~ible. Su¢h
17 limit~ are shown &Ghema~is:ally in f igure 11 a~ numeral~ 53 and 54
18 for upper and lower limi~ re~;pec~iYely for radiation detector
19 ¦ 20, and at numerals 55 and 56 ~or upper and 10WeE limits
20 ¦ respectively for radiation det~ctos 21, for a ~epre~entative
21 ¦ accumulation of ice, de~ianatad at numeral 57.
22 ¦ Becau~e of the po6~ibili~y of accumulatlo~ of flawed ice~
23 ¦ respon~e~ of th~ radlation detec~or~ do no~ determine unig~e ic~
2~ ¦ ~ccumulatlon~, Instead, each radiatlon detector re~pon~e
2S descr ibe6 a band of pO88 ible ice accumulation~, bou~ded by an
.
~ .
~ 3~3
upper lce accumulaitorl limit and a lower ice accumulation limit,~
2 determln~d by the calibratlon c:urve~0 For e~ample, for radiation
3 detector 20 ~ he responE~e 6~ in f lgure 12 de~cribe~ a band of ice
4 accumulations bour1ded by an upper ice ~ccumulatlon limi. 63 and a
5 lowsr lc~ accllmulation limit 64. Likewi6e" for radiation
6 detector 21 l the response 65 de~cribe~ a band of ice
7 accumulat~ons bounded by an upper ic:e accumulation limit 66 and a
8 lc~wf~r lce accumulation l~mit 670 For any ice accumulation~
9 re~pon~e6 from rad iation detector~ 20 and 21 must be compatible
10 because both ~adiation detector~ are responding to the ~ame ice
accumulatiot~p This compatibili y requ~rement res r~ctz
12 interpretation of ~hese re~pon6e~ to interpretation~ for whit:h
13 t~e ice accumulation bands overlap. For example~ the respor;se~
1462 for r~diation detector 20 ~nd 65 for radiation detector 21
l~i combine ~o lndicate an actual ice accumulatlon ln the range ~B in
16 f igure 12.
17In addition~ re6ponses from the radiation detector~ may
18 ~nclude a si~uation in which an i e ~ccumula'cion limit ~or one
19 ¦ radiatlon detector i8 the ~ame as an ice accumulation limit for
20 the other radiation detector,. 1:3camples o~ such a ~ltuation are
21~hown by the limlts 71 and 72 and the limits 73 and 74 in ~lgure
22 13. Th~ ~ituation can only occur for an acc:umlllation of watex
23 or of per~ect ice~. :E3ecau3e accumulations o~ per~ect ice are
24 ~ robable J thi~ ~ ituation . is normally interpreted a~ an
25 ac:cumulat~on ~f water, uslle~ the temperature s~ or indicates a
,
. - .
~ ~:7~i3~3
1 ¦ temperatllre less th~n the free:zing temperature of water. Then~
2 ¦ if the temperature ls leEi~ than the freezir:g temperature of
3 ¦ water, the c:or~b:lned response~ of radiation detectors 20 and 21
4 ¦ are lnterp~eted as lndlcatlng an accumulation in 'che range
5 ¦ determir~ed by the upper and lo~er ~ce ac:cumulation llmits.
6 ¦Salt on a pavement may lower the freezing temperature o~ the
7 ¦ water on the pavement t SO that water ~ ins~ead of ice ~ may be on
8 ¦ the pavement, even when ~he ~emperature ~ensor indicate~ a
¦ temperature below the fre~zing temperature of water. Elowever,
' 10 ¦ lnterpretation of the respon~e as ice in this ~nstance i~ a
11 ¦ s::on~ervative interpretation because lc:e will be indicated wher
12 ¦ the accumul~tion i~ actually unfrozen.
13 ¦Other mea~urements, such as impedance b~dge measurement~ of
14 ¦ the resi~tallc~ or tbe capacitance between elec~rcdes which would
15 ¦ be mounted flush with the eacpo~ed surface, c~n alAo be u ed in
16 ¦ con junction w~th re~ponBe~ from ~he r~diation detec:tors ~o
17 ¦ distingui~h accumulatiorl of lce from accumulations of water
~8 1 Therefore, although in this preferred f:mbod$merlt a temperature
19 ¦ ~ensor is used to ~ssist in d$~tinguishing arcumula~io~s of ice
~ ¦ from accumulations Df wate t operativn of thifi ice accumulation
21 monitor ~ not limited to an embodlment using a temper2ture
22 sensor ~OE this purpo ec
~3The ~ur~ace reflectivity o~ a ~oil- or mud-covered e~po~ed
24 ~r~e 14 i~ very low, ~o that when the expo~ed ~ur~ace beoomes
~5 coYered with ~oil or w~th mud~ nearly all of the emitted
,
~ 3
¦ radiation 1B transmltted lnto the ~oil or mud, instead of being
2 reflected a ~he expo6ed surface 14~ Ab~orptlon of radiation by
3 ~oil or mud ~ very high, ~o that after being transmi'c~ed into
4 the soil or mud on the e~posed sur~ace 1~ nearly all of the emitted
5 radlation is ab~orbed by the ~oil or mud,, ~herefore~ when the
6 e2~posed surfac~ i8 covered by ~o~l or by mud, tbe amount of
7 rad iation reflected to 'che radiation detector6 abruptly becomes
8 negllgible, be~ause ~uddenly nearly all o ti e emitted radiatlon
9 becomes ab~orbed by the ~oil or mud.
Responses from both radiation detec:t~rs will also be
11 negl~glble for very thick accumulations of lc:e. This . ~tuation
12 18 d~stlngui6hed from soil or mud depo~its by a g~adual decrea~e
13 in radiatiorl detectors~ xe~pon~es a~ ice accumulates, in c:ontra~t
14 with the abrupt decrease associated with ~oil or mud depo~ltsO
15 Theref ore the presence of ~o il 1 c~r mud on the e:~posed surf ace :14,
16 and the conseqllent need for cleaniRg the eYpo~ed surface, 1~
17 indica~ed by abrupt decrea~ef; in radiation detector re~pon~esO to
18 values whlch are also not greater than a charac:tPristic thre~hold
19 value ~or o~l or mude The thre~hold valu~ kha'c characte~i~e~ a
20 soil or mud-covered e~:po~;ed ~urface is determined by calibration
21 with soil- or mud covered e:Kpozed ~urace!; 0
22 The preceding discus~ n about in~erp~eting radaation
23 detector~ ' r~F:pon~es $~; incorpora~d into a series of logical
24 step6 to eliminate the ef~ect o~ amblent radiation on the
25 mea~ureDIent~ to indica~e and measure ~c:e accumula~iong~g
,' ~ ' . . - ' ~"'
..
- : .
.. ' ~ ' - ,
' ' .
' 3:~
1 ~75
¦ including accumulation6 of flawed ice~ to 8ignal when lce
2 ¦ accumulatlon has reached a critical th$ckne~8~ and to distlngui~h
3 ¦ accumulations of water from accumulation~ o~ i~e. By way of
4 ¦ example, such steps are indicated in figures 14a and 14b. Other
5 ¦ sequences of steps could also be ~Ised to interpret the radiation
6 I detectors' responses, but the sequence shown in figures 14a and 14b
7 ¦ contains the essential aspects of the interpretation. The interpre-
B ¦ tation is perEormed humanly or electronically.
¦ The interpretat~on re~ulrez the respanse-ac:~umulation
10 ¦ calibrat~on curves; 51 and 52, temperature-sensor c:alib~ation
¦ data, and he ~oll/mud threshold value, herein iden~lfied by MIJD.
12 ¦ If it is desired to signal an ice accumulation warning for
13 ¦ a~cumulations greater than a c:ritlcal accu~nulation, a value ~or
14 ¦ this critical accumulation~ herei~ identi~ied by CRIT, mu~t also
15 ¦ b~ ~upplied"
16 ¦ If electronic interpretatlon i8 tD be performed ~ elther
17 ¦ tabular or an analytic representa~ion of the calib~ation curves
18 ¦ ls stored in memory prior to starting the interpretation Values
19 for MI~D and CRIT, an arbikrary value, ~, for C~?mparing presen~
20 ~and prev~ous values of correc~ed radia~ion detec'cors' respon~es,,
21 and an arbitrary value, ~, ~or comparing acll:umulation limlt~3" are
22 also ~tored ill memory . Fo~ manual interpretation ~ graphlcal or
23 analytic ~epre~entatiorls of the calibration~ will no~emally be
24 used 0
~i Input data ~or the in'cerpreta ion a~e ~he ~cesponse o~
2-~
.
~ . .
, ': ' ' :
.
.~''
'
.
.
l ~2~53~3
- 1 ¦ radiation detes~or 20 while t:he emi~ter 1~3 of ~ ~ h~rein de~iynated
2 ¦ D9t and while the emitter i; on, herein de~;ignated Dlj t~e
3 ¦ respon~e o radlation detec~or 21 while t~ em~ter i~ off,
4 ¦ hereln deslgnated D10, and while the emitter i8 on~ be~el;rl
5 ¦ defilgnated D2; and the ~e pon6e of the temperature sensor, hereln
6 ¦ designated TEMP. In figures 14a and 14b these inpu~ data are
7 supplied from a readout device 77, such ~s a voltmeter, which is
8 switched between the output of radiation detector 20, 78, the output
9 o~ radiation detector 21, 79, and the output of the temperature
0 sensor, 80, to obtain the desired input data. In figur2 14a,
responses from the ice accumulation monitor 15 are shown as being
12 transmitted by a data cable 44. In some situations it will be
13 preferable to transmit the ice accumulation monitor responses by
14 telemetry, and this can also be readily accomplished by those
skilled in electronic data transmission.
16 Interpretation begins ~y as~3igning the value ~l-D~ 'co Vl and
17 the value D2-DlO to Y2, 81. Vl ~nd Y2 the~ repreE;ent detecto~
18 respon~e~ that haYe been correc~ed tv ellmir~ats the e~fect o~
19 ambient radiation . Subseque~t intea:pretation i~ based on Yl and
2() V2~, ~o ~e~e a~ignmentE; elimir;a~e the effect of amb~erlt
21 radiatiorl from the iLntarpretation0
22 The inte~pretation c:ontinue6 by dete~m~ning lf ~oil or mud
23 i8 pra~ent on tbe e:~po ed l3u~:Eace,D V~ and V2 are each compared
24 with the ~30~1~mud threshold value, 82 ~ 83, and i~ either Vl or Y2
ls greater than he threshold value, the interpretatio~ f~r ic:e
.
,
~- ~ ' ., . ~ .
' . -
~ , . ' ':
: ' :- ,' '
'~
~2~7~3~3
l c4n~cinue~0 If both Vl and V2 are les~ than the ol:L/mud
2 thre~hold ~ Vl and V2 are compared with heir values VlP and V2P
3 fram the previou~ cycle, 84, 85, to determine 1~ there ha~ been
4 an abrupt decrease in e~ ther Vl or V20 If there ha6 beerl an
5 abrupt decr~a~e in Vl or V2, a depo~it of ~oil or mud ~B
6 signalled 86. In figure 14 a depo~iit of soil or mud i8 ~iynall~d
7 a~ a diaplay on a monito~e 87. Alterna~ively a warning llght or
8 any Q her warnlng alarm could be actuated by the ~ollJmud 8i9n211~
After signalllng a deposit of ~o~l or mud, the interpretation
10 procedure ~top~ and awalts the cleaning ~d re~tartlng of the ice
11 accumulation morlitor.
12If there has noS been an abrupt decrea~e in either Vl ar V2,
13 or if eithgr Vl or V2 is greater than the threfiJhold value ~ the
14 interpretation continues by d~3term~ning the upper accumulation
15 bound, TMAX g and the lower accumulat lon boulld, TMIN. Vl ~8
16 compared with ~che calibration curve 51 for radiation detector 2
17 lto determ~Lne the ma~cimum accumulation a~i~oclated with Yl~ Tl~AX,
18 and the minimum accumulation a~soc ~ ated with Vl, Tl~IN~, 88.
19 Al~;o~ V2 is comparPd with the calibration s:~urve 52 ~or radiation
20detecto~ 21 to det~rmine the max1mum accumul2'cion a6~0ciated wlth
21 Y2, T2~iAX, and the minimum accumulation a~ociate~ with Y2~
22 T2~I~a, 89~ ~he upper accumula~lo~ bound i~ th~r~ tbe le~er .of
23 ~lPlP~X and T2NP.X ~ 90, and the lower accumulation .bound i~ the
~4 greater o~ Tlæ~IN and T2MIN, 91.
2~; . ~he interpretation then oontinue~ by dete~m~n~ng wheth~r the
.. . ., _
,
' '"~ '
' ~: . - ' .:
.
~ i3~
-1 accumulatis:)n i~ water or iC~13,. When water accumulates on the
2 e~posed Rurfac:e" tbe temperature i~ above freezlng, and one ~et
3 of accumulation bound~i ~or radiation detector~ 20 and 21
4 coincide~ such a~ 1DdiCa~ed by the ~oun~fi 71 and 72" or the
bound~ 73 and 74 in figure 13" ~c:cumulation bound~ coincide i,
6 I, bo~h upper bound~ are the ~;ame, II, botb ~ owex bounds are it!be
8 same, or III ~ the upper bound ~rom one curve i5 the same as the
lower bound flrom the o~her curv2. The~e po~ibili1;ies are
checked 92~ 93, 94~ d lf, to withln a ~3mall differenc:e, ~, non~
of the accum~alation bounds are lthe ~ame d th~ accumulation s:an no .
11 be water~ Therefore an accumulatlon of ice is p~esent, and
12 e ither;
13 1. An ~ce accumulatiom and the upper ~nd lower
14 accumulat~orl bound~ are ~ignalled, 95~ and recorded and~or
15 di6played, a~ de6$red 87, and the procedure is read~ed for th~
16 next set of data 96; or
17 2~. The upp~r accumulation bound iL8 compared with tbe
18 c:ritis:al acGumulatlon,r CRIT, 97, a warnlng i8 ac~uate~ 98 i the
19 accumulation e~ceeds CRIT or the wiarning i~ not actuated i~ the
20 ¦ accumulation i~ le~ than CRIT~ and tha procedure ~s read~ed for
21 ¦ the next s~t o~ data 96~ or
22 3 " The~3~ alternatives alre combined ~o that upper and lower
23 accllmulation bounds are signall~d 95, and reco~ded and/or
24 d i~play~d, a~ de~ired 87, }le accumulation i~ evaluated ~o
25 determine lf it i; a critical ~ccumulation 97, a warnirg i~
ll 27
.. _, _ _ , . _ .. , , .. , . . . _ .. ....
.
, .
~53~3
1 ¦ actuate~ lf ~h~ ac:cumulation ea~ceedfi CR3:T 98 ~ and the procedure
2 ¦ i~ read ied for the ne~ set o~ d~ta 96 ~,
3 ¦ In figures 14a and 14b, the alterrlative of testing for a critical
4 ¦ accwnulation is indica-ted by dashed lines, and the occurrence of
5 ¦ a critical accumulation is shown as actuating an active highway
6 ¦ warniny sign 98. Instead of actuating a highway warning sign,
7 ¦ warning lights, horns, or othr alarms, could also be actuated,
8 ¦ to suite the needs of the particular application.
¦ If any o~ the accumulation bounds do coincide, t~e
10 ¦ temp~rature is checked 99 and if th~ temp~orature i~ great~r than
11 1 zero degr~e~ Cels:ius" wa~er i8 ~iignalled ~00" and an ppropriate
12 ¦ mes~age i~ di~played on a mon~tor 87. If the temperature i~ less
13 ¦ than zero de~ree~ Celsiui ~ an accumulation o~ ice 1~; present, arld
14 ¦ either.
15 ¦ l. An ic:e ac:cumulat~Lorl and the upper and lower
16 ¦ accumulal~ion bound~ are ~;ignalled 95, and xecorded and~or
17 ¦ di~played~ a~ d~3~ired 87, and the pro~edure i~ readied for the
18 ¦ next ~;et of data 96; or
19 ¦ 2. The upper accumulation bourad i~ co~p ~ed ~:Lth ~he
~ I c~itlcal accumulationO CP~IT~ 97" a wa~:n~ng ls actua~ed 98 if the
21 ¦ accumulatlon e~ceed~ CRIT or the wa~ng i~ not actua ed if the
¦ accumulatio~ less than CRIT, arld the procedure i~ ~eadied ~or
23 1 ~he next ~t o~ data 96; or
24 3,, ~hes~ alternatives a~e com~in~d 130 that upper and lower
25 at:e~.~ulaltivr~ bounds ara ~igr~alled 95~, and reco~ded arld/or
28 .
'. ~ . : ' ~ ' :
~ , . . .
,''- :. ~ .
.
~ ~t7~3~3
-1 displayed~ a des~red 87, the accumulation i~ eYaluated to
2 determine ~f it i6 a critical accumulatlon 97, a warning i~
3 actuated if the accumulation e~cgeds C~IT 98, and the procedure
4 i6 readied for ~h~ next ~et of data 96 a
In addltion, inS~antaneou~ accumulation rate~, or average
6 accumulatlon rates ~or any de lred time int~rval~ can be readily
7 determined by storing m~asu~ed accumulation limits, taking
8 differences o accumulations, and divid$ng by the appropxiate
time interval.
By using this ice accumulation monitor 15~ many pers4ns will
11 be rellably informed of when~ and how mucha ice is being formed~
12 generally in places and on 6urfacss wher~ it is not wanted9 and~
13 if de6ired, per~ons can be warned when critical accumulation
14 limlt~ are exceeded, informed of accumulation rate~ and warned
when accumulation rat~s are dangerou~ Then appropriate mea~ures
16 can be taken to remove ~he lce or to mitigate against it~
17 consequencesO
18 ~
lg In addition~ o~al refl~c~ion at the bare eYposed ~urfac~9
with part~al transm$ssion at a covered e~posed surface and total
21 reflectio~ at the s~b~equent air interfaceO and calib~ation
22 curves similar to ~he responses 51 and 52 in figure 11~ will al~o
23 be ob~ained for accumulat~on~ of other transpar~nt ~ubs~3~ce~p
24 such a8 ethyl alcohol or ~.hyl ether~ whicb haYe inde~ sf
refraction le~ than the index 3~ refraction of the ~ri~m.
-
..
~ ~7Si33~3
3 ¦ Therefore, a~plic:al:lon of this accumula~ion monitor i6 not
2 ¦ re~tricted to measuring accumulation~ of ice or of water; but3 ¦ with calib~al:lons for th~se other 6ubstances, this accumulat1on
4 ¦ monitor will al~o mea6ure ~cs~umulatlons of the~e other sub~tanc:e~
5 ¦ and d istinguish accumula~is)n~ of the sol id form from
6 accumulations of the l~quidO
'10
11 I
12
13
161
17
lB
~9 ..
21
22
~3
24
2~
,, ~'
. ~ '
