音叉.ppt

音叉式限位开关
周晓
物位产品经理Endress+Hauser China
Slide 1
周晓
上海销售中心地址:
上海市田林路388号
新业大楼八楼
邮编: 200030
电话: (021)54902300
传真(021)54902302
E-mail:.
.com
北京销售中心地址:
北京朝阳区朝外大街22号
泛利大厦7层10号
邮编: 100020
电话: (010)65882468
传真:(010)65881725
E-mail:.
.com
周晓
Endress+Hauser Shanghai
物位产品经理
2
周晓
物位仪表 Level Measurement
电容式物位仪表
Capacitive Level Measurement
音叉式限位开关
Vibration Level Limit Switches
超声波物位仪
Ultrasonic Level Measurement
微波式物位仪
Microwave Level Measurement
静压式液位计
Hydrostatic Level Measurement
伽玛射线
Radiometric Level Measurement
重锤式物位仪
Elec.-Mech. Level Measurement
差压式物位仪
Differential-Pressure Level Transmitter
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周晓
液体音叉
Liquiphant II
Liquiphant M
Liquiphant Failsafe
Liquiphant T
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周晓
液体音叉
IN LIQUIDS
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周晓
音叉–原理
symetrical 2 rod
sensor (frequency
shift limit switch)
drive
receiver
straight vibration rod
bent vibration rod
»
Df
vibration fork
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周晓
alternating voltage
causes the piezo to
expand and contract
individual crystalshave a fixedalignment and are polarised
voltage applied like poles reject
- press -
voltage applied
unlike poles attract
- crystals elongate -
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音叉–原理
7
周晓
Common
electrode
Driver
alternating voltage
causes the piezo to
expand and contract
Force
individual crystalshave a fixedalignment and are polarised
voltage applied like poles reject
- crystals
compress -
力
力
Receiver
音叉–原理
8
周晓
fault
immersed length[mm]
120
fa-10%
fa
fa+ 5%
600
f (Hz)
fa = fork resonance frequency in air (approx. 400 Hz )
fa-10% = switch point
fa+5% = corrosion alarm ( 60 s delay )
f < 120 Hz = alarm function ( s delay, 10 s by PMF,
. broken piezo wire, no power supply )
f > 600 Hz = alarm function ( s delay, . device error )
50
0
0
fault
normal operation
switch point
ALARM
ALARM
音叉–原理
9
周晓
changing liquids
foam
gas bubbles
build - up
electrial propertie