在40年代，過(guò)程控制是基于3～15PSI的氣動(dòng)標(biāo)準(zhǔn)信號(hào)。其后，由于4～20mA模擬信號(hào)的使用，使得模擬控制器得到了廣泛應(yīng)用，但是并不是所有的傳感儀表和驅(qū)動(dòng)裝置都使用統(tǒng)一的4～20mA信號(hào)。70年代，由于在檢測(cè)、模擬控制和邏輯控制領(lǐng)域率先使用了計(jì)算機(jī)，從而產(chǎn)生了集中控制。進(jìn)入80年代，由于微處理器的出現(xiàn)，促使工業(yè)儀表進(jìn)入了數(shù)字化和智能化的時(shí)代，4～20mA模擬信號(hào)傳輸逐步被數(shù)字化通信代替，加之分布式控制以及網(wǎng)絡(luò)技術(shù)的迅速發(fā)展，促進(jìn)了控制、調(diào)度、優(yōu)化、決策等功能一體化的發(fā)展。然而由于檢測(cè)、變送、執(zhí)行等機(jī)構(gòu)大都采用模擬信號(hào)連接，其傳送方式是一對(duì)一結(jié)構(gòu)，這使得接線復(fù)雜，工程費(fèi)用高，維護(hù)困難，而信號(hào)傳輸精度底，易受干擾，儀表互換性差，這都阻礙了上層系統(tǒng)的功能發(fā)揮。另一方面，由于智能儀表的功能遠(yuǎn)遠(yuǎn)超過(guò)了現(xiàn)場(chǎng)模擬儀表，如對(duì)量程和零點(diǎn)進(jìn)行遠(yuǎn)方設(shè)定，儀表工作狀態(tài)實(shí)現(xiàn)自診斷，能進(jìn)行多參數(shù)測(cè)量和對(duì)環(huán)境影響的補(bǔ)償?shù)?。由此可?jiàn)，智能儀表和控制系統(tǒng)的發(fā)展，都要求上層系統(tǒng)和現(xiàn)場(chǎng)儀表實(shí)現(xiàn)數(shù)字通信。計(jì)算機(jī)及網(wǎng)絡(luò)技術(shù)與控制系統(tǒng)的發(fā)展有著緊密的聯(lián)系。早在50年代中后期，計(jì)算機(jī)就已經(jīng)被應(yīng)用到控制系統(tǒng)中。60年代初，出現(xiàn)了由計(jì)算機(jī)完全替代模擬控制的控制系統(tǒng)，被稱為直接數(shù)字控制（DirectDigitalControl,DDC）。70年代中期，隨著微處理器的出現(xiàn)，計(jì)算機(jī)控制系統(tǒng)進(jìn)入一個(gè)新的快速發(fā)展的時(shí)期，1975年世界上套以微處理為基礎(chǔ)的分散式計(jì)算機(jī)控制系統(tǒng)問(wèn)世，它以多臺(tái)微處理器共同分散控制，并通過(guò)數(shù)據(jù)通信網(wǎng)絡(luò)實(shí)現(xiàn)集中管理，被稱為集散控制系統(tǒng)
M7030S-0003
ERA-4662
PAS57-0-200-400
MR-S12-80B-Z33
ATOX48RG01100000
Y-GC-02-009
546-G4983-1
MPA-09-460-196
MPM-190ZFRMM-AM
446964-01E
CP-06-30S-S
MPA-25-184
MPA-35-460-167
MPFLX230X35A
MPFLXI230X08BY08
MPM1141RE-1176
MPM1901FRMM-427
MPM1902FRM-418
MPM-1904-1550
MPM-1904R-1198
MPM3202-R1-1405
MPA-25-124
269PLUS100P120
735-5-5-HI-485
750P5G5S5HIA20R
750P5G5S5HIA20RE
PQMT20CA
T60G03ACHF8HH6MM
MCR1V-DCU-001-E1
1336F-B050-AA-EN-GM6-HAS2-L5
AUXL-111
MDM212H2V
NACHI MDM212HIV USPP MDM212HIV
NACHI MFM352H1V USPP MFM352H1V
NACHI MFM452H5V NSPP MFM452H5V
NACHI MFM452H5V USPP MFM452H5V
NACHI MFM552H1V USPP MFM552H1V
NACHI MFM552Q3V USPP MFM552Q3V
NACHI MSM302H4V1 NSPP MSM302H4V1
RAX11
RBX1100
SC35-BJ1-S-A
SC700DL-AX20
UM139-20
USADED-37-FC43
A4-N46-2-11-415
ER920-13812
ER920-17812
Nanometer Technologies MCP 12 Mass Connector Polisher
Nanometer Technologies MCP 24 Fiber Optic Polisher
Nanometer Technologies MCP 24-60C Fiber Optic Polisher
NANOMETRICS 7200-2161 REV P1,115VAC 5AMP 50/60HZ,OLYMPUS OPTICAL 12V 50W HAL-L
NANOMETRICS MULTI-WAVELENGTH ELLIPSOMETER CONTROL MODULE EC110,UR80-0.01,2SS 32-
NANOMETRICS NANOLINE IV line width measuring system
Nanometrics Trident Digitiser 13885R3-01
NANOMOTION HR-8 ceramic motor 28mmx28mm X - Y Stage & AB5 driver
NAP361000 Square D Circuit Breaker NAL361000 NAP 1000A
Narda 4745-69
NARDA 8718B RF SURVEY METER/8723D PROBE/ PKG
NARDA 8718B RF SURVEY METER/8723D PROBE/ PKG 2 NIST CALIBRATION
Narda A8722D
NASA Thermal Imager / Infrared Camera 600°C To 1600°C, T.P. 1400°C
NASA ARTIFACT VPI Vehicle Power Interface Rack & Console Hubble Space Telescope
NASARC INTELLIGREAM MP REAMER ROBOTIC NOZZLE TORCH CLEANING STATION IRM010001-MP
NASH VACUUM PUMP MODEL CL 2001
NASH VACUUM PUMP MODEL CL2002
NASH VACUUM PUMP MODEL CL701
National AC Servo Motor ACF-1212E2-E0S, ACF1212E2E0S, ACF-1212E2-EOS
NATIONAL AERONAUTICS GEL-0700 LASER SYSTEM COUNTER
National Industrial 330 KVA 4160 X 460/266 Volt Dry Type Transformer - T27
National Institute of Standards & Technology; Phase Noise Measurement System
National Instrument cDAQ-9178 8-s USB Chassis w/ NI 9221 & 9472
NATIONAL INSTRUMENT NI-CFP-2020 NSFP NICFP2020
NATIONAL INSTRUMENT NIPXI-4472 USPP NIPXI4472
National Instrument PXI-1006
NATIONAL INSTRUMENT VME-MX1-2
National Instruments 777119-32 VXI-PCI8015 Windows, No Cable ( )
National Instruments 900851E Debug Deployment Environment 3.5
National Instruments Acoustic Data Acquisition System - Sound Level Measurement
National Instruments cDAQ-9178, NI 9213, 9203, 9265, 9264, 9205, 9485
NATIONAL INSTRUMENTS EVS-1464RT REAL TIME VISION SYSTEM FOR GIGE/1394 CAMERAS
NATIONAL INSTRUMENTS MID-7654 4-AXIS SERVO MOTOR DRIVE
National Instruments NI 185014-01 PCI-4451
National Instruments NI 185014-01 PCI-4451 Tested
National Instruments NI 185014-01 PCI-4452
National Instruments NI PCI 4461 Tested
National Instruments NI PCI-4472 8-Channel Dynamic Signal Ac Tested good
National Instruments NI PCI-4472 8-Channel Dynamic Signal Acquisition Board/Card
NATIONAL INSTRUMENTS NI PCI-5114 250 MS/s, 8-Bit Digitizer/Oscilloscope
Nationa