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电容式位移传感器 S 极板的遮盖面积,单位为极板的遮盖面积,单位为m2;极板间介质的介电系数;极板间介质的介电系数;两平行极板间的距离,单位为两平行极板间的距离,单位为m;0 真空的介电常数,真空的介电常数,0=8.85410-12 F/m;r 极板间介质的相对介电常数,对于空气介质,极板间介质的相对介电常数,对于空气介质,r 1。)(130 S S Cr极板极板1极板极板2图图3-1 3-1 变极距型电容传感器变极距型电容传感器C00 0CC0 0图图3-2 3-2 C C-特性曲线特性曲线)(23000000 CS S S C00 SC)(3310000 CC时,当10/)(4313020000 .CC)(5300 CC所以变极距型电容传感器在设计时要考虑所以变极距型电容传感器在设计时要考虑满足满足 0 0的条件。且一般的条件。且一般 只能在极只能在极小的范围内变化。小的范围内变化。)(73120200 SCKr)()(631000020%r1000011 CSCCC1000021 CSCCC0201,02100 SC C1 1C2 2时,当1/0.13020001CC.13020002CC)(8322300021 .CCCC)(123200 CCK)(11310010020030%r)(103200 CC)()()(9312402000 CCS C 0,0)(1331100 CS CCC,00CC)(143100 axCxab CCCxbaxaxCC0D0D1La圆柱形电容式线位移传感器圆柱形电容式线位移传感器:筒长L)pF/C;cm/L(DDln.LC,DDlnLCrr10010008012成线性关系。与aLaCDDaLCr,ln1201001xCC1C2C3)(1530321 abCCCCxx1CBld2d12xCACACBC)(1632110 ddblC)(173 111212211ddxlbddbxCCCBA)(183121212100 ddlxCCC2r22r1hhxC2C1C)(19322120120 KhAr/rlnhr/rlnhCxx1202r/rlnK1202r/rlnhAxxKhAr/rlnhr/rlnhC12012022pF.lnm.)m/pF.(rrlnhCmin46418402185822120pF.pF.)r/rln(h)r/rln(h )r/rln(h)()r/rln(hCrmax0787124641222212012120120图5-5 变面积型电容传感器原理图 L.m.m.hdV623521450422L/pF.L.pF.pF.VCCKminmax190623546410787RP(a)CRLC(b)UCr1C(a)RRUSCCr1R(b)RCr2USCU(c)USCUCr1Cr2CC(d)UCr1Cr2USCLLCr1Cr2USCUCr1Cr2USC相敏相敏检波检波CxC0UUSCIiIxIxixxiiIICjIUCjIU00)(20300 CCUUxiS CxSCUUi00(a)C2C1UERLR1R2i1i2+0-R2R1RLC2C1D1D2iC1iC2+UE+(b)UE+i2 R1R2C1C2RL+i1 在负半周时,二极管在负半周时,二极管D D2 2导通、导通、D D1 1截止,电截止,电容容C C2 2很快被充电至电压很快被充电至电压U UE E;电源经电阻;电源经电阻R R2 2以以i i1 1 向负载电阻向负载电阻R RL L供电,与此同时,电容供电,与此同时,电容C C1 1经电阻经电阻R R1 1、负载电阻、负载电阻R RL L 放电,流过放电,流过R RL L 的放电电流为的放电电流为i i2 2。流过。流过R RL L的总电流的总电流i iL L 为为i i1 1 和和i i2 2 的代数和。的代数和。0-R2R1RLC2C1D1D2iC1iC2+UE+22CRRRRRtexpRRRRRURRRUiLLLLELLE20220222111CURRRRTdtiTdtiTIELLT22TCRRRRRLL1121CURRRRTIELLC2122102CCTU)RR(RRRRIIRRRRUELLLLL2)(2LLLRRRRRR)(243210 CCUfKUER2D1D2ABR1C1C2U0FUrG+-+-QQRS双稳态触发器A2A1QQQQtuAuAuBuBuABuABUFUFUGUGUrUrUrUr-U1U1T1U1-U10000000000T2U1U1U1U1T1T2ttttttttt(a)(b)差动脉冲调宽电路各点电压波形图U012121211UTTTU UTTTUBA,)(2631122211111 UUUlnCRTUUUlnCRTrr)(27312121121212110 UTTTTUTTTUTTTUUUBA)(283121210 UCCCCU UddU100 USSU100L)CCC(fc01021)(32321010 LCCCCfffcLCf21cCCCC01振荡回路固有电容振荡回路固有电容传感器电容传感器电容引线分布电容引线分布电容Cxf振荡器振荡器uf限幅限幅放大器放大器uL鉴频器鉴频器0,0 fC Cxf振荡器振荡器uf限幅限幅放大器放大器uL鉴频器鉴频器Q Q
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