数据采集基础英汉对照.ppt

1、Basics of Data Acquisition 数据采集基础,Typical data acquisition applications数据采集典型应用,Physiological studies（生理学研究） Environmental studies (temperature, etc.)（环境研究） Materials testing（材料试验） Medical research（医学研究） Quality control and testing（质量控制与试验）,Typical data acquisition applications数据采集典型应用,Strain, press

2、ure, temperature and vibration analysis（应力、压力、温度、振动分析） Fluid analysis（流体分析） Manufacturing automation（制造自动化）,Components of a data acquisition systems数据采集系统的组成,Analog to digital conversion (A/D) 模数转换器 Digital to analog conversion (D/A) 数模转换器 Digital input/output (DIO) 数字输入/输出 Pacer clock 同步时钟,Analog t

3、o Digital Conversion (A/D)模数转换器,Once data has been converted from analog to digital, the digital information can then be processed by the computer, or transferred to memory 将模拟信号转换成数字信号以便被计算机进一步处理或传送到内存中,Digital to Analog Conversion (D/A),D/A converters convert stored data back to a continuous signa

4、l (analog voltage) for display or control purposes（数模转换器用于将存储的信号再变成模拟电压，以供显示和控制） Output from the D/A converter can be used to drive external devices which require an analog input（模数转换器的输出可用于需要模拟输入的外部设备的驱动）,Digital Input/Output (DIO)数字输入/输出,Used primarily for control purposes 用于控制 Used to transmit da

5、ta between the host processor and an external digital device that expects to receive 1s and 0s 处理器和外部数字设备之间的数据传递,Pacer Clock同步时钟,Used to initiate repetitive data conversions 重复数据变换的初始化 Used to control the sampling rate of conversions 采样率的控制,What is analog?何谓模拟量,Analog signals are “continuous” signal

6、s 模拟信号是“连续”信号 Represented by continuously changing physical quantities 用连续变化的物理量来表示 Level of signal can be increased or decreased indefinitely 信号的大小可以无限增加或减小 Ex. temperature, pressure, strain, voltage 如，温度、压力、应力、电压,What is digital?何谓数字量,Digital signals are “discrete” signals 数字信号是“离散”信号 Represented

7、by separate, individual units “bits” (binary digit) 用分离、独立的单位，比特表示 Bits are represented by one of two possible states: on/off, true/false, 1/0 比特代表两种量：开/关，真/假，1/0,What is data acquisition?何谓数据采集,A method of acquiring an analog signal and converting (digitizing) it into a binary code which can be man

8、ipulated by a computer 是一种获取模拟信号并将其转换成二进制代码的一种方法。 通过计算机来实现,Computer,Analog Signal,Analysis,A/D Interface模数转换接口,Converts analog data into digital data which can be processed（将模拟信号变换为数字信号以用于后续处理） Typical components（典型组成） Multiplexers（多路转换开关） Amplifiers（放大器或调理器） Sample and hold circuits（采样及保持电路） A/D co

9、nverters（A/D变换器）,A/D Converter FunctionsA/D变换器功能,Input and output (I/O)（输入/输出） Analog input is converted into a digital number, by comparing the voltage with its position within the Full Scale Range（将模拟信号以一个数字表示并与满量程电压中其相应位置的电压值进行比较） With an n-bit A/D converter the number of output levels equals 2n

10、e.g. 12-bit converter = 212 = 4096 （对于n位模数转换器，输出电平等于2n,Full Scale Range (FSR)满量程,Full scale range refers to the largest voltage range which can be input into the A/D converter 满量程对应于能够输入至模数转换器的最大电压值,Range量程（测量范围）,Range is an input span for an A/D and D/A system（量程：A/D和D/A系统的输入范围） Typical ranges are

11、based on available sensors（典型地，取决于传感器） Uni-polar (positive)（单极性） 0 to 5 volts 0 to 10 volts Bipolar（双极性） -5 to +5 volts -10 to +10 volts,Full scale range examples例子,+10v,0v,+10v,+1.25v,-10v,-1.25v,FSR = 10v,FSR = 20v,FSR = 2.5v,Input/Output输入/输出,Analog,Digital,(101110010011),Resolution分辨率,Resolution

12、 determines the smallest change that can be detected 分辨率决定了能够检测到的最小变化量 Specified in bits. Determines number of output levels, or steps 8 bits = 256 steps 10 bits = 1024 steps 12 bits = 4096 steps 16 bits = 65,536 steps,Typical Resolutions应用领域,8-bit common for image capture 图像捕捉 10-bit general analog

13、 acquisition 通用模拟量采集 12-bit general analog acquisition 16-bit precision analog acquisition 精密模拟量采集 24-bit high-accuracy analog acquisition 高精度模拟量采集,Output Levels/Resolution Example例子,1-bit A/D Converter,1,0,+10v,0v,Output Levels/Resolution Example,2-bit A/D Converter,11,00,+10v,0v,10,01,Output Level

14、s/Resolution Example,4-bit A/D Converter,+10v,0v,1111,1110,1101,1100,1011,1010,1001,1000,0111,0110,0101,0100,0011,0010,0001,0000,Output Levels/Resolution Example,12-bit A/D Converter,1111 1111 1111,0000 0000 0000,+10v,0v,4096 Output Levels,Output Levels/Resolution Example,16-bit A/D Converter,1111 1

15、111 1111,0000 0000 0000,+10v,0v,65,536 Output Levels,LSB,LSB stands for “least significant bit” 最小有效位 An LSB represents the smallest change that can be resolved by the A/D converter 代表了AD所能分辨的最小变化量 LSB = Full Scale Range (FSR) 2n,What affects conversion speed? 影响变换速度的因素,A/D converter only （仅由AD本身性质决

16、定） A/D converter and related circuitry （AD变换器及其相关电路） A/D system and host （AD系统和主机）,Acquisition time采集时间,The time required to perform a complete conversion from the analog signal to digital （从模拟信号转换为数字信号所需要的完整时间） The time required after receipt of “start digitizing” command until the A/D converter ha

17、s finished digitizing （收到“开始数字化指令”到数字化完成的时间）,Settling time延迟时间,Time it takes to switch to a new channel 从一个信号通道到另一个通道所需的时间 Each time a user switches between channels, there is a delay, referred to as settling time 通道之间相互转换的时间，也称为延迟,Throughput rate总传输率,The inverse of A/D conversion time + acquisition

18、 time AD变换+采集时间 - 时间的倒数 Measured in Hertz (Hz), which means the number of conversions per second 以赫兹来表征 The maximum rate at which the data conversion system can operate, while maintaining a specific accuracy 指在保持足够精度条件下数据变换系统能够执行的最大速率。,Throughput总时间,Acquisition System The acquisition system determin

19、es the maximum throughput possible （采集系统决定了可能的最大总时间） The entire system (host, disk, A/D board, and program) determines the practical throughput （实际系统由主机、硬盘、数采板和程序大小、速度来决定）,Throughput,Throughput is specified as an aggregate of all channels （定义为所有通道的集总时间） A/D runs at a constant rate （AD以固定速率运行） Number

20、 of channels determines throughput per channel （通道数决定了每通道的传输时间） The host computer and software must be able to service the A/D board before the next conversion is complete,Speeding up throughput rate提高总采样率的方法,Overlap mode - while one sample is in Sample and Hold circuitry, the next is read into the

21、multiplexer （重叠模式） Throughput equals the greater of conversion time OR acquisition time, plus any time needed for Sample and Hold switching （总采样时间等于变换时间或采集时间较大者加上“采样保持”时间）,Getting signals into the computer将信号送入计算机,Transducers convert physical variables into electrical outputs 传感器将物理变量转换成电输出信号 An inp

22、ut transducer (sensor) then supplies its output to signal conditioning circuitry (on a Screw Terminal Panel) 电输出信号然后被送入信号调理电路 Signal conditioning circuitry prepares for interfacing with the PC 信号调理电路通过接口与计算机相连,Amplification放大器,The output of a sensor usually requires amplification Apply gain 一般来讲，每一种

23、传感器都需要放大器,Gain增益,A scale (multiplying) factor which increases an input signal to better utilize the range of the A/D converter 是一个标尺，将输入信号放大，以更好地利用AD变换器的量程,Gain,Gain is the amplification applied to a signal to bring it to the range of the A/D system High Level Gains (PGH) for high level signals 1, 2

24、, 4, 8 Low Level Gains (PGL) for low level signals 1, 10, 100, 500,Selecting Gain and Range增益和量程的选择,0 volts,10 volts,User Input,Selected Range (uni-polar),Only 50% of the available A/D range is used. 增益：1：1，仅使用了满量程的50%,Selecting Gain and Range增益和量程的选择,-10 volts,+10 volts,User Input,Selected Range (b

25、ipolar),Only 25% of the available A/D range is used. 对于双极性AD，增益为1，仅使用了25%,0 volts,Selecting Gain and Range增益和量程的选择,-10 volts,+10 volts,User Input,Selected Range (bipolar),Only 25% of the available A/D range is used.,0 volts,Gain Amp,10,Selecting Gain and Range增益和量程的选择,1 volt,0 volts,-10 volts,10 vol

26、ts,User Input,Selected Range (bipolar),Using this range only utilizes 1/20th of the range. This would allow the input to be divided into 205 increments. 对于12位AD，分辨率=1/（20/4096）=205,0 volts,Selecting Gain and Range增益和量程的选择,1 volt,0 volts,0 volts,1.25 volts,User Input,Selected Range (uni-polar),Using this range utilizes 8/10ths of the range. This would allow the input to be divided into 3277 increments. 对于12位A