1、RF Admittance Basics Theory of Operation 射频导纳仪表基本原理和操作,What is Point Level?什么是点位控制?,Point level or On/Off measurement indicates the absence or presence of material at a certain point in the vessel, pit, pipe, etc 点位控制或开关量测量指示的是在容器或深井或管道里某一点被测介质的有无Point level measurements are used for 点位控制主要应用于 High
2、Level高液位测量 Spill Prevention溢出保护 Stop Fill 停止溢出Low Level 低液位测量 Stop Empty防止空罐 Refill Indication填充指示 Pump Protection泵保护,Dielectric Constant (K)介电常数 (K),The Tank and Probe form a Capacitor 罐壁和探头形成一个电容,C =,k A,d,C= Capacitance in pF 电容 pF k= Dielectric Constant of material介电常数 A= Area of the plates探头测量区
3、域 d= Distance between plates探头与罐壁距离,A,k air = 1,d,C,k oil = 2,The Tank and Probe form a Capacitor 罐壁和探头形成一个电容,C =,k A,d,C= Capacitance in pF 电容 pF k= Dielectric Constant of material介电常数 A= Area of the plates 探头测量区域 d= Distance between plates 探头与罐壁距离,k,k air = 1,A,d,C,k oil = 2,Affects of Dielectric
4、and Conductivity介电常数和电导率对电容值的影响,Vertical Insulated Probes 垂直的绝缘探头,Inches of Level 液位高度,C p (pF),0,10,20,30,绝缘探头 Insulated Probe,油Oil,水Water,Affects of Dielectric and Conductivity 介电常数和电导率对电容值的影响,Vertical Bare Probes 垂直的非绝缘探头,Inches of Level 液位高度,C p (pF),0,10,20,30,油Oil,水Water,Bare Probe 探头,Properti
5、es of Material 物质的特性,A Materials physical property does not affect RF Admittance measurements.物质的物理特性 不会影响RF Admittance 测量. RF Admittance uses the products electrical properties to make the measurement. RF Admittance 利用的是物质的导电特性来进行测量的.,Dielectric Constant (k) Scale 介电常数范围,1.0006,1.3,2.5,9,18.3,33.6,
6、37,56.6,80+,Air空气,Poly Chips聚乙烯,Most Hydrocarbons多数碳氢化合物,Phenol苯酚,Isopropyl Alcohol异丙醇,Methanol甲醇,Ethylene Glycol乙烯,Tap Water and Most Acids自来水和大部酸,Sand沙子,4.8,D.I. Water除盐水,1.6,Propane丙烷,1,Vacuum 真空,Methyl Alcohol甲醇,Conductivity (g) Scale 导电率,1,.001,10K,50 - 500,Kerosene 煤油,Methyl Alcohol甲醇,Orange J
7、uice 果汁,Tap Water自来水,Beer 啤酒,1250,D.I. Water 除盐 水,30% H2SO430% 硫酸,2,1M,Sea Water 海水,80K,90% H2SO490% 硫酸,2,The Capacitance Disadvantage: 电容式测量的缺点:,Affected by Conductive Coatings 挂料会影响测量,The RF Advantage: 射频导纳的优势:,Not Affected by Conductive Coatings 抗挂料,Cote-Shield Mounting Consideration Cote-Shield安
8、装用于抗挂料,Cote-shield must extend at least 50mm (2”) through the mounting and past any build up Cote-shield 最少 50mm (2”) 这样安装才能起到抗挂料作用,Cote Shield Demonstration Cote Shield 演示,Point Level Tuning Fork 点位测量 音叉,Tuning Fork Operation 音叉的操作原理,Tuning fork uses piezoelectric crystals to drivethe fork and make
9、 it vibrate at approximately 1200 Hz. 音叉是利用压电晶体产生振动频率(1200赫兹)来进 行工作的 When the tuning fork is covered in the productthe frequency changes 当音叉被物体覆盖时振动频率发生改变 . The frequency change is detected by the internal oscillator and converted to a switching command 频率的改变会被内部的震荡器检测出来并把它转换成开关输 出,Tuning Fork 音叉,Th
10、e TF-100 series tuning fork is to be used on clean liquids only TF-100 系列音叉 仅仅是用于纯净液体的测量的 Liquid applications that contain air are not a problem for the tuning fork. 液体中含有气泡对音叉无影响 . Tuning forks should not be used on liquidsthat coat or crystallize. 音叉不能被用于产生黏附和结晶的液体测量,Tuning Fork 音叉,Independent of
11、electrical characteristics 不受被测介质介电常数的影响 Trip point repeatability 2mm重复精度 2mm Short Insertion Lengths可以截断插入深度 Measure total level in non-dedicated vessels 可以测量液体液位 Clean liquids纯净的液体 Will measure liquid level under foam 可以测量泡沫以下的液位 Ignores Foam忽略泡沫影响,Point Level Ultrasonic 点位测量 超声波,Theory of “Gap Sw
12、itch” Operation 超声波测量开关的原理,Piezoelectric crystal on one side of the gap transmits acoustic energy Piezoelectric crystal on the other side of the gap acts as a receiver for this energy超声波测量开关有两个极板一个极板的压电晶体产生能量并且传送能量,另一个极板接收能量。 With air or gas in the gap the energy is not sufficient to cross the gap t
13、o the receive crystal 在空气或气体中能量不足以在两个极板间传送,Theory of “Gap Switch” Operation 超声波测量开关的原理,Liquids transmit acoustic energy more effectively than air or any other gas液体的声波能量传导性好于气体 When liquid fills the gap, the acoustic signal signal travels though the liquid to the receive crystal causing the output t
14、o go to the alarm condition (high level当液体充满在两个极板间的时候,声波传导能量增大因此产生报警,Gap Switch 超声波测量开关,Gap switches are for clean liquids 超声波液位开关用于纯净的液体测量 Gap switches should not be used on 超声波液位开关不能应用以下测量: Liquids with entrained air内部含有气泡的液体 Liquids with suspended solids含有悬浮物的液体 Coating liquids 有黏附性的液体,Gap Switch
15、 超声波测量开关,Independent of electrical characteristics 不受被测介质的介电常数的影响 Trip point repeatability 1/16”重复精度 1/16” Short Insertion Lengths可以截断插入长度 Measure total level in non-dedicated vessels 可以测量液体液位 Clean liquids纯净的液体 Will measure liquid level under foam 可以测量泡沫以下的液位 Ignores Foam忽略泡沫影响,Common Point Level T
16、erminology 点位测量技术的共同点,Integral vs. Remote 整体 与分体,Fail Safe安全保护,High Level Fail - Safe 高液位安全报警 Relays de-energize when materials touches sensing element当介质接触到探头时,继电器会翻转 Low Level Fail-Safe 低液为安全报警 Relays de-energize when material leaves the sensing element当介质离开探头时,继电器会翻转,Installation Orientation 安装方向
17、,C = KAD,Time Delay 时间延迟,Differential区别,Relay energizes and de-energizes at different points along the sensor.继电器动作与不动作在一个传感器的不同点上,Linepower vs. 2-Wire 供电模式 与. 2-线制比较,2-Wire Current Output 两线制电流输出 Intellipoint and ThePoint ,Or Field Changeable too,What is Verify? 校验是什么?,A test which mimics a high le
18、vel condition without actually raising the level in the tank 模拟高物位状态进行仪表测试. Available on 主要用于: High Level Only高液位报警测试 RF Intellipoint (Two Wire or Line Power)射频导纳RF Intellipoint两线或线路供电产品 Ultrasonic line powered and two wire VeriGAP超声波线路供电和两线 VeriGAP产品 Ideal for Overfill and Spill Prevention 用于溢出保护是很
19、理想的,How RF Verify works 射频导纳是如何完成校验工作的,Intellipoint The Intellipoint product runs an Auto-Verify check 3 times a second Intellipoint 产品运行自动检测功能每秒三次 The test compares the current capacitance to the air capacitance and indicates a fault due to loss of sensing element or disconnected wiring自动测试是通过比较空气中
20、的电容值并且指示报警由于传感器磨损或错误连线 The manual Certify button adds capacitance through software to mimic a high level condition手动测试按钮通过模拟电容值通过软件模拟高液位状态,How VeriGAP Verify Works 超声波开关是如何校验的,When the Verify is activated, the signal from the “send” crystal is boosted, and the signal is transmitted through the body
21、of the sensor, simulating a high level alarm.当校验功能开启时信号从传感器的发射端发出模拟高液位报警,What is Certify?什么是校验?,Certify is a manual verify check initiated by a magnetic key or push button. This manual certify checks the electronics, sensor and crystal bonding (Gap switches), and actuates the relays to check the entire control loop. 手动校验是用按键开始启动的.这种手动校验检测电子板,传感器和晶体发生器(超声波开关)并且激活继电器来检验整个控制回路.,Questions? 问题?,
