Sensing Technologies of IoT

Sensing Technologies of IoT

Outline

• One-dimensional barcode
• Two-dementional barcode
• IC card
• RFID
• Sensor
• Positioning and GPS
• Smart device

2.1 One-dimensional Barcode 一维条形码

One-dimensional Barcode

BarCode 工作原理

• optical machine-readable representation of data.
  相关的数据的光学机器可读表示法.
• varying the widths and spacings of parallel lines.
  改变平行线的宽度和间距来表示数据的.
• Each character is represented by a pattern of wide and narrow bars.
  每一个字母是用一条细线代表的。
• As it moves, barcode reader uses a photosensor to convert the barcode into an electrical signal.
  在扫描器移动过程中其能把条码变成电子信号。
• Every barcode begins with a special start character and ends with a special stop character.
  每个条形码都以一个特殊的开始字符开始，以一个特殊的结束字符结束。
• Some barcodes may include a checksum character just before the stop character.
  有些条形码可能在停止字符之前包含校验和字符。

BarCode 具体形式

name	特点 1	特点2
UPC-A	for product
UPC-E	small items	automatically re-inserting
Codabar	for libraries, blood banks
EAN-13	marking retail goods	countrycodes
Interleaved 2 of 5	for warehouse and industries
Code 39	for government and industries
Code 93	more compact version of Code 39
Code 128	excellent density	support all ASCII symbols
Bookland EAN	for books, video, audio and software

• UPC-A

  • identifies the manufacturer and specific product
    识别制造商和具体的产品

    
    
    UPC-A

• UPC-E

  • for labeling small items

  • automatically re-inserting them at the scanner

    
    
    UPC-E

• Codabar

  • for libraries, blood banks

    
    
    Codabar

• EAN-13
  • for marking retail goods. 零售商品

  • 2 or 3 characters countrycodes + 9 or 10 data digits + 1 checksum

    
    
    EAN-13

• Interleaved 2 of 5
  • for warehouse(仓库) and industries

Interleaved 2 of 5

Interleaved 2 of 5

• Code 39
  • for government and industries

Code 39

• Code 93
  • more compact（紧凑） version of Code 39

Code 93

• Code 128
  • excellent density for all-numeric data and good density for alphanumeric data.
    对全数字和字母的数据有很好的密度
  • support all ASCII symbols

Code 128

• Bookland EAN (ISBN)

  • for books, video, audio and software

    
    
    Bookland EAN

BarCode Reader 工作原理

• light source, a lens and a light sensor translating optical impulses into electrical ones.
  光源、透镜和光传感器将光脉冲转换成电脉冲。
• contain decoder circuitry 译码器电路

BarCode Reader 具体形式（不重要）

BarCode Reader Type	特点
Pen-type readers	light source and photodiode
Laser scanners	laser beam & mirror
CCD readers	light sensors
Camera-based readers	camera and image processing
Omni-directional barcode scanners	Laser scanner, for grocery

• Pen-type readers: consist of a light source and photodiode 光源和光电二极管
• Laser scanners: laser beam 激光 mirror 棱镜反射扫描
• CCD readers: light sensors 光传感器
• Camera-based readers: camera and image processing
• Omni-directional barcode scanners(全方位的条形码扫描仪): Laser scanner, for grocery

BarCode System

• encoding module for generating a visually significant barcode
  生成具有视觉意义的条形码
• decoding module for receiving an acquired version of a visually significant barcode
  接收可能在典型的文档处理通道
• recovering the message
  恢复

2.2 Two-dimentional Code

工作原理

• encode a lot of information in a small space
• contain 100 to about 2000 characters

具体形式

• PDF-417

  
  
  PDF-417

• DataMatrix

• QR Code

2.3 IC card

工作原理

• embedded integrated circuits
  嵌入式集成电路
• provide identification, authentication, data storage and application processing.
  识别、认证、数据存储和应用程序处理。

具体形式

• smart card

  
  
  smart card

• chip card

  
  
  chip card

• integrated circuit card

  
  
  integrated circuit card

Contact smart cards 工作原理

• comprising gold plated contact pads
  包括若干镀金接触垫
• power is supplied by the card reader.
  电源由读卡器提供

Contactless smart cards 工作原理 (重点)

• RF induction technology 无线射频技术
• not have an internal power source 没电
• communicate with a terminal via radio waves
  通过无线电波与终端通信
• Contactless smart cards do not contain an ordinary readonly RFID, but they do contain a re-writeable smart card.
  非接触式智能卡不包含普通的只读RFID，但它们包含可重写的智能卡
• used for identification,authentication, and data storage
  可用于识别、认证和数据存储

应用场景

• Financial: ATM cards, fuel cards, mobile phone SIMs.
• Identifications: driver's license system, students card
• Healthcare: portable medical record

2.4 RFID

定义和特点

• RFID Radio Frequency Identification：Radio-frequency identification is the use of a wireless non-contact system that uses radio-frequency electromagnetic fields to transfer data from a tag attached to an object, for the purposes of automatic identification and tracking.
  射频识别:射频识别是使用无线非接触系统，利用射频电磁场将数据从附着在物体上的标签传输到物体上，以实现自动识别和跟踪。
• An ADC (Automated Data Collection) technology
  • uses radio-frequency waves to transfer data to identify, categorize, track
  • fast and doesn't require physical sight or contact
  • automatic
  • low cost
  • unique identification

RFID 组件

• RFID tag
• RF Antenna
• Network

• WorkStation

  
  
  RFID Components

RFID tag

• The tag contains electronically stored information.
  标签包含电子存储的信息，可以从几米(码)外读取
• the tag does not need to be within line of sight of the reader.
  标签不需要在阅读器的视线范围内
• Tags can be read-only or read-write

RFID Tag 概念图

RFID

name	名字
Antenna	天线
Power Supply	电力供应
Tx Modulator	Tx调制器
Rx Modulator	Rx调制器
Control Logic	逻辑控制模块
Memory Cells	记忆模块

RFID Tag 分类（重点）

Type	Battery	Range	其他特点
Passive	non-exist	Short	reflects radio signal
Semi-active	exist
Active	exist	High	Tag actively transmits radio signal

Type	Change
Read-only tags	never
Write once	once
Read/Write tags	over time

• Passive 被动

  • Operational power scavenged from reader radiated power
    从读出器辐射功率中清除的操作功率
  • Tag reflects radio signal from reader
    标签反射来自阅读器的无线电信号
  • Reader powered
  • Shorter Read Range

• Semi-active 半主动

  • Operational power provided by battery

• Active 主动

  • Operational power provided by battery - transmitter built into tag
    工作电源由内置在标签内的电池发射器提供
  • Tag transmits radio signal
    标签传送无线电信号
  • Battery powered memory, radio & circuitry
    电池供电的存储器，无线电和电路
  • High Read Range

• Read-only tags

• Write once, read many tags

• Read/Write tags

RFID Reader （重点）

• 功能

1. Remote power tags 远程电源标签
2. Establish a bidirectional data link 建立双向数据链路
3. Inventory tags, filter results 库存标签，过滤结果
4. Communicate with networked server(s) 与联网的伺服器通讯
5. Can read 100-300 tags per second 每秒可以读取100-300个标签

Frequencies of operations for Readers

Type	Frequency	Speed	Range	Penteates	Antennas Scale	Construction
Low-Frequency	30-300 kHz	slow	minimal	well except iron	Large	thick & complex & expensive
High-Frequency	3-30 kHz	mid-slow	0.7m	well except iron	Large	thin
Ultra High Frequency	300 MHz - 1GHz	fast	>1.0m	well in iron except else	Smaller	thinner
Microwave	2-30 GHz	very fast	greater	well in iron	Smaller	thinner

RFID 交流模型（重点）

communication

• Host 发出命令
• Reader 和 Tag 通过射频信号进行通信
• Reader 产生 Carrier signal
• Reader通过 Antennas 发送 Carrier signal
• Carrier signal hit Tag
• Tag recieves 并修改信号发送回Reader
• Antennas 接收并发送到 Reader
• Reader decode
• Reader 发送结果到 Host

Electronic Product Code EPC码

• universal identifier 通用标识符
• RFID tag
• EPCglobal Tag Data Standard
  其结构定义在EPCglobal标签数据标准中

EPC Network (PPT 要求理解)

• 定义
  The EPCglobal Network is a computer network used to share product data between trading partners. It was created by EPCglobal.
  EPCglobal网络是一个用于在贸易伙伴之间共享产品数据的计算机网络。它是由EPCglobal创建的。

• The EPCglobal Network consists of the following components:

Name	翻译
Object Naming Service (ONS)	对象命名服务(ONS)
EPC Discovery Services	EPC发现服务
EPC Information Services (EPCIS)	EPC信息服务(EPCIS)

2.5 Sensor

定义

A device that responds to a physical stimulus and transmits a resulting impulse.

A sensor is a converter that measures a physical quantity and converts it into a signal which can be read by an observer or by an (today mostly electronic) instrument.
传感器是一个转换器，它测量一个物理量，并将其转换成一个信号，该信号可以被观察者或(今天主要是电子)仪器读取。

分类

Type	特点
Active sensors	generate electric current
Passive sensors	require additional other electrical energy
Contact sensor	requires physical contact
Non-contact sensor	no physical contact

Classification

Input & Output

• Input: stimulus or measurand (temperature, pressure, light intensity)
• Output: electrical signal (voltage, current, frequency, phase)
• Relation:
  • Linear or nonlinear; single/multiple
  • inputs, single output;

Range and Span

Example: a sensors is designed for: −30 °C to +80 °C
to output 2.5V to 1.2V
Range: −30°C and +80 °C
Span: 80− (−30)=110 °C
Input full scale = 110 °C
Output full scale = 2.5V-1.2V=1.3V

Error

• Error Source

name	名字
materials used	材料
ageing	老化
operational errors	操作错误
calibration errors	校准错误
noise	噪音

• Error 分类

name	time dependent	cause
Static errors	NO
Dynamic error	YES
System error		imperfect design of the measurement setup
Random errors		uncontrolled variables

一堆概念（重点）

• Resolution(分辨力): the minimum increment in stimulus to which it can respond.
  最小感知单元的大小
• Accuracy(准确度): how closely the output will match the true value.
  感知信息的准确程度

• Precision(精确度): how close the measured values are to each other.

  
  
  Accuracy & Resolution
  
  
  Accuracy & Precision
• Reliability(可靠性): reproducibility, indicates the ability of the device to perform its stated function.
  也称为再现性:在不同时间测量时，传感器在相同条件下不能表示相同的值(即刺激或输入)。
  对设备质量的一种统计测量，它表明设备在正常运行条件下，在规定的一段时间或若干个周期内不发生故障的情况下，执行规定功能的能力。
• Sensitivity(灵敏度): represents the slope of the transfer function.
  传感器的灵敏度定义为给定输入变化(通常是输入的单位变化)的输出变化。灵敏度表示传递函数的斜率。
• Hysteresis(滞后程度): the deviation of the sensor’s output at any given point when approached from two different directions
  滞后程度:当传感器从两个不同的方向接近任意给定点时，传感器输出的偏差
• Linearity(线性度)： the deviation of the output from a best-fit straight line for a given range of the sensor
  线性度: 在给定的传感器范围内，输出与最佳拟合直线的偏差
  Response time(响应时间): delay time, indicates the time needed for the output to reach steady state for a step change in input.
  表示输出达到稳态所需的时间。
  Calibration(校准): the experimental determination of thetransfer function of a sensor.
  校准:传感器传递函数的实验测定。
  通常，当传递函数未知时，
  当设备必须在低于制造商规定的公差下运行时。
  例如，在0到100°C的温度范围内，使用容忍度为5%的热敏电阻来测量温度。

2.6 Positioning and GPS

定位基本原理（重点）

Signals in the electromagnetic spectrum
Signal time transit from known points converted to distance
Distances/ directions to known points are solved for the unknown position

电磁波谱中的信号
信号时间从已知点转换为距离
由多个已知点的距离/方向由未知位置求出

• Cellular positioning- EOTD 细胞定位

Cellular positioning

GPS

• Global Positioning System
• GPS provides:
  ① Location or positional fix
  ② Velocity
  ③ Direction of travel
  ④ Accurate time
• GPS Basic Steps:

Step	Name	Usage
1	Positioning	知道SV的位置
2	Timing	知道准确时间
3	SV Ranging（卫星测距）	算出物体到SV的举例
4	Trilateration（三边测量）	找到物体在地球上的交叉点
5	Correction of errors	Correcting for delays

• Range from each satellite calculated
  range = time delay * speed of light

• Sources of Errors

Name	名字
atmosphere	大气
Satellite clock errors	卫星时钟误差
SV position errors	SV位置误差
Quality of GPS receiver	GPS接收机质量
Multi-path errors	多路径误差