Capacitive sensing

Claim 1

means defining with a body to be sensed a variable capacitance, a fixed-value capacitance, and a voltage source connected to the fixed-value and variable capacitances to define a capacitive voltage divider, and means /or detecting the voltage across one arm of said divider. 2, Capacitive sensing means according to claim 1, wherein 4,aid detecting means is connectediacross the fixed- value capacitance. 3 Capacitive sensing means according to claim 1 or 2, P wherein Said voltage detecting means is a diode" detection ao circuit in the form of a voltage double circuit. .n 0 4. capacitve sensing means according to claim 1 or 2, S wherein said voltage detecting means is a circuit including 0 a JFET in common-drain configuration. Capacitive sensing means according to any preceding claim, including an array of four metal or metallized plates oo *comprising a capacitive sensor, said array, considting of a first plate which constitutes the 'live' electrode of said ao variable capagitance and also constitutes one plate of the S, fixed,-v~~3 capacitance, a second plate forming the other plate S" ,t the fixed-value capacitance, a third plate held at th? same potential as the secondplate to form with the second plate a screened region within which circuitry is housed, and a fourth -plate defining a grounded screen to reduce the influence of stray fields and metal objects on the measurements. 6. Capacitive sensing means according to any preceding claim, wherein two spaced sensors are utilised to provide information on height, roll and pitch. 7. Capacitive sensing means according to any preceding claim, when used in a sheep shearing operation to detect the distance between a shearing device and a body to be shorn. 8. Capacitive sensing means according to claim 7, said means being located on a surface of a wool or the like shearing device and including means fca reducing the effect of the wool SAND D3- IAU 1'27 "V a VVI' -13. 1 ke material to be jhorn or on the sensing means, forisacn the wool or like in terial be'tween the sensinig means. arid, a body -~to be shorn as the sheazring device engages the wool or like. riaterial. 9. Capaciti-\esernsing means. according 'to claim 8, wherein said means 'is-a- sh-ield J9evi-ce arranb' ed to overlie the sensors. Capac- tive sensing means according to claim:9, wherein the shield has sides 'Which extend around s&aid, sensors. apqtieen M~ reans according to claim 10, wherein' t '~ielda s is mounted to theserindvcebacopat -,unting. 1*2~ Capacit ai:i means accora .ing,,ito6any preceding vo 4 'i 'ei 7&-odes oj plates used in the sensor *are thin metallic layers on an insulating substrate. 13.. Capacitive -sensing means, according to any' prededing 44 claim,, wherein the or each sensor is mounted on 'a sheari.Tig, device a.t an angle of less, than S0 8 to the plaine the sole ~f the cutter. C) 14.' aTacitive sensing means according to claim 13, ,wherein said arigle is in the range 30 to 590 15. Capacitive s0tnsinq means substantially as herein 0 4. describe4 witl-refqrence to Figures 1 to 12 and 14, 1 to'12, and 16, or 17 to 19 of,.the accompanying drawings. l. A shearing device including a cfapacitive sen~ing 'means,, substantially as herein described-with reference to Figure s 1 an d 14,'J 15 arid 16, as modified by Figures 2 to 12 or' 17 to 19 the accompanying draiwngs. 17, 'A method of capacitively sensing at least distance, substantially as herein described, 18~ The articles, things, parts, elements,, steps, fea-4pres, 1< methods, processes, compouinds arid compositions referre~ to or indicated in the 'sprci fi cation and/or claims of. the application individually or collectivety, and, any -and all combinations of any twio or more of such. 0 I <9 f'7 ti~t escp~In w~uu o tns i timon, inciuding the best Method of performing it known DATED THI\13 17TH DlAY OF AUGUST, 1984~ //I THE UNIVERSITY OF WETEN AUSTR2\LIA A- By its Paten~t AtorneyS:) SANDERCOCK, SM BEADI1~bK NI Fellows Institute ofP tn Attorieys, of, Aus ralia. K' 'K (K, -N 0 KK' K' ~9 *t~ -K I K I? K' 'ZN ~-NV C- 1) 'K) 0. K' I, F' Thej'invention provides capacitive sensing means includifiq exoqed electrode means defining with a body to be sensea variable capacitance, a fixed value capacitApce,'and a, voltage U I W 'IM I i I I I.; I J. Sd-. L .JL -AL L I LL 'I ~may be connected to a robot arm. Shears 16 are earthed. Each capacitive sen~sor 12 has a characteristic of the form shown I,, corn i~n Figureza 2, where 18 is t17le ir dielectric "and, 20 the, wool, diele~cri,. The linear part of this curve can b1e described I 0 gT~ I. 0 -0 'y ~j. /1 0' II G2 64/84 '0 Al ga* *0 44 4 4 to, CL)4 "4.4 4 4404 ,44~ 4 4.44 04 4.4 4 4 44 4 44 44 .4 ~4 4 4 4444' 44 4 44 44 4 4 *4* p 44 O 444 'I -in 2. I O'Z. 4 1/ /1j/ i~ 999 9 V 4 .9 V 9 .9 9 9 $4 9 4 a 9 4 0 0 990 4S* B N *49 4 4 6 OSCILLATOR M~~Az- L-OW PASS FILTE't= 10-4s TNS~ouc~jj SC1-IDTT" DIODlES OJAA. A: LMAB-E 47k 0/P 47 K IN -4 AM1PV.IER (MPIN -V) "n ~,isona;' Cx disc1haAges and'~ charges. ~2 All Figure, 9 a graph showing the, 6harge pumpingl{ S .5 S S S SO SQ S S .00 0 S 0 0 S SO 0 0 0 0 0 0 050 S S S SO S S S S 5.5 5 0 0 J OSC1LLATUR O~z. Ku A' TRM~SUCIR OV-'oV ER (GI= 2 "p -32 064/84 44.4 9 #4#4 4, 44 4 4 4944 44 9 4 ~4 44 94 4 '4 4 4 4444 4 44 9 9 94 444 4 94 4 4, 494 'I I FXlo s M1\ A *1 i~i) 4 -0*0* 4 *0 4 4* 0* 4* 4 4 .4*4 4~ 4 4 *4 'a 4444 4 *0 4. 4 *4 .4 4*4 A .'TlME -Z lco~ 'U 1 Cc *4 0 w 1~~b 4 4 04 40 44 \I c. 4 4 0 4Y 9 fo 0 04 0 0 0* 4*40 4 44 4 N j *4 ~~rn ~WAG~iAT a t 44* a) 1.01- I I I aw. 106 OCLATMt MEQUENCf (LODG CM ~'0 Cgs gate-source capacitance Cgd- gate-drain capacitance K I J~H3 L~ B £~4 16 PO* B 0 7fffT 14 00*0 6. I, it /oI 4 4 44 4 4 4, 4 44 *4 4 <1' 444 4 44 4 *4 44 4 4 ~d lop4 Ij 44 44 4 444 I Ii .00.@ 0*0 0 0000 0* S 0*0e 0* II 49 0 Ii Ii 9 4?-z Offfy. 6 application individually or collectiv,ely, and any and all I' combinations of any two or' more of such. .4 J r~ 7, '/7 1) OSCLLATOCS de~ p .1oc p p 1*1 PP p I, p. 4~ P p p 17- I, p 4~oPP P.. p PpI~ 'p. p pp P P P pp., Pp 0 p ID PP pP 0. p. P. P OK lot qD I1 1I K I p av /v 0- K. C:> 1000 19 44 600 .4 4, 4 4 4, 500 400 4 4 4 4 *4 4, 100 4* 4, too I/d 11mm L~O.O~ 0.- .3Om~ii .4 9- hJ