從控制速度上看，繼電器控制系統(tǒng)依靠機(jī)械觸點(diǎn)的動(dòng)作以實(shí)現(xiàn)控制，工作頻率低，機(jī)械觸點(diǎn)還會(huì)出現(xiàn)抖動(dòng)問(wèn)題。而PLC通過(guò)程序指令控制半導(dǎo)體電路來(lái)實(shí)現(xiàn)控制的，速度快， 程序指令執(zhí)行時(shí)間在微秒級(jí)，且不會(huì)出現(xiàn)觸點(diǎn)抖動(dòng)問(wèn)題。

在60年代，汽車生產(chǎn)流水線的自動(dòng)控制系統(tǒng)基本上都是由繼電器控制裝置構(gòu)成的。當(dāng)時(shí)汽車的每一次改型都直接導(dǎo)致繼電器控制裝置的重新設(shè)計(jì)和安裝。隨著生產(chǎn)的發(fā)展，汽車型號(hào)更新的周期愈來(lái)愈短，這樣，繼電器控制裝置就需要經(jīng)常地重新設(shè)計(jì)和安裝，十分費(fèi)時(shí)，費(fèi)工，費(fèi)料，甚至阻礙了更新周期的縮短。為了改變這一現(xiàn)狀，美國(guó)通用汽車公司在1969年公開(kāi)招標(biāo)，要求用新的控制裝置取代繼電器控制裝置，并提出了十項(xiàng)招標(biāo)指標(biāo)，即：

(1）編程方便，現(xiàn)場(chǎng)可修改程序；

(2）維修方便，采用模塊化結(jié)構(gòu)；

(3）可靠性高于繼電器控制裝置；

(4）體積小于繼電器控制裝置；

(5）數(shù)據(jù)可直接送入管理計(jì)算機(jī)；

(6）成本可與繼電器控制裝置競(jìng)爭(zhēng)；

(7）輸入可以是交流115V；

(8）輸出為交流115V，2A以上，能直接驅(qū)動(dòng)電磁閥，接觸器等；

(9）在擴(kuò)展時(shí)，原系統(tǒng)只要很小變更；

(10）用戶程序存儲(chǔ)器容量至少能擴(kuò)展到4K。

(4700) Siemens Circuit Breaker 35A ED63B035 3P 18Ka LD LUG

(4711) Cutler Hammer Circuit Breaker KT3225T 3P 225 Amp

(4723) Square D Circuit Breaker KAL36150 150A 3 P 600V

(4738) Gould Modicon Input True Low B353 24 VDC

(4740) Mirada Research CNG Cylinder Valve C-50985 3,600 Psi S/N: M-00266

(4741) Mirada Research CNG Cylinder Valve C-50985 3,600 Psi S/N: M-00272

(4750) Lot of 3 Allen Bradley Z-34040 Contact Kit 3 Pole

(4794) Westinghouse Circuit Breaker MCP13300CR 30A 3P 600 VAC

(4795) Westinghouse Circuit Breaker 15 Amp MCP03150CR 3P 600VAC

(4802) Siemens Simatic Digital Input 6ES5 420-7LA11 24VDC

(4808) Stromberg Power Amplifier 807430 2X30A/24V

(4820) RKC PCB Control Board C4UP33Y2

(4830) Allen Bradley Magnetic OL Relay 810-A351811-1

(4831) Allen Bradley Magnetic OL Relay 810-A351811

(4850) emecanique Limit Switch XCK-J5954B21 240VAC 3A

(4854) Cutler Hammer Safety Switch 100A 3P 600V DH363FRK

(4855) Modicon Input Module 16PT AS-BDEP-218 115VAC Isol

(4883) Allen Bradley Flex Input Module 1794-IA16 & 1794-TBN

(4889) Triconex Communication Module / 5 Cable 7400078-100 EICM4107

(4897) Atlas Copco Control Board 1900.0591.11

(4911) Allen Bradley Size 3 Contactor 500F-DOD920 2P 90A

(4916) Temposonics MTS GHS0240UD602RO Linear Transducer w/ Probe & CD

(4951) Druck PTX-1210 Pressure Transducer 100Psi 4-30 VDC

(4970) Allen Bradley Servo Module 1771-HS3A 3Axis

(4971) Allen Bradley PLC5 I/O Module 1771-DB /B

(4975) ABB Circuit Breaker UXAB718530R999 350A 3P 600V

(5002) Fisher Electronics Proximity Sensor RT 1110.03 2974 NWOB

(5003) Akron Standard Analog Input Card 440-0027-01 PC Board

(5011) GE Terminal Board 531X305NTBANG1 ACDC 2000 - SUPER CLEAN

(5024) Toshiba PC Control Board ARNI-845B1-R02-3G

(5025) Omron Power Supply C500-PS212-E 3G2A5-PS212-E 24 VDC

(5042) Lucas Schaevitz Pressure Sensor 0-30 psi P4063-0005

(5043) Lucas Schaevitz Pressure Sensor 0-30 psi P4064-0005

(5044) PCT Instruments Pressure Sensor 0-2000 PSIG PZA2KGC

(5054) Fanuc Memory Board A16B-1210-0381/01A

(5064) Siemens Auxiliary Switch A01FD62 Molded Case Circuit Breaker

(5071)B Allen Bradley Motor Controller 154-A11NB 400-480 VAC 11 Amp

(5098) Thalheim Encoder ITD40B14Y28 1024

(5134) Honeywell Pressure Control P455A 1022 Flame Control

(5135) Allen Bradley DC Control Relay 700DC-PH200Z24 35 A 2NO

(5136) Yokogawa Pressure Transmitter YA 11F-SMS4/FMF1/COM-B 24V DC 2000 Psi

(5137) Square D Pneumatic Timing Relay 120 V Coil 9050-BO26D

(5141) Conveyor Control MSD-2-700BG Conveyor Motion Control Tachometer

(5144) emecanique I/O Module Relay TSX 171 2028 20 DC 110-240 VAC

(5145) Allen Bradley Zero Speed Switch 808-E1 50-200 RPM 600V

(5160) GE Circuit Breaker SGDA3AT0400 240V SGD 3P 400A

(5178) Allen Bradley Servo Controller 1394-AM03

(5186) Chromalox Temperature Controller 3390-77777-0

(5204) Mercoid Pressure Switch Mercury 2-15 Psig PG-804-P1

(5226) Siemens Power Interface Board for DC Drive A1-106-100-531

(5232) Banner Photoelectric Scanner Head 27082 OSBLVAG

(5241) United Electric Pressure Switch 3-30 Psid 316SS 1/2" J400KS147B

(5247) Cutler Hammer Circuit Breaker 30A 3P 600VAC FDB3030L

(5249) Cutler Hammer Circuit Breaker 100A 3P 600VAC FDB3100L

(5266) ABB Contact Kit EHWCK160-3 3P

(5281)B Allen Bradley Gravity Return Limit Switch 802G-GP Nema 1

(5290) Allen Bradley Contactor 775-NX22 4P 90A @ 600V 24V Coil

(5301) Honeywell Temperature Controller DC330B-KE-000-20-OAOOOO-OO-O Digital

(5305) Cutler Hammer Circuit Breaker 60 Amps HFD3060 3P 600 VAC

(5306) Cutler Hammer Circuit Breaker 70 Amps HD3070 3P 600 VAC Molded Case

(5309) Cutler Hammer Magnetic Contactor C10CN3A Size 1 120V Coil W/ Interlock

(5329) Cutler Hammer Photoelectric Detector 1261B-100 9 FT Cable

(5332) United Electric Pressure Switch J7-9676-218 0-30 HGV 1.5 HG 15A 125/250V

(5339) Allen Bradley Input Card 1746-IO12 6PT 115 VAC SLC500

(5348) Moore Signal Conditioner Isolator Converter SCX/4-20MA/4-20MA/5 .5VLP-FA

(5356) Thermo Electric Plug Assembly CO-42503-KX-4MP

(5362) Woods Control Card PC332 Drive Board

(5365) Moore Industries Signal Converter SCT/4-20MA/4-20MA/117AC

(5369) Reliance Electric Remote I/O Head 120/240 VAC 57C330

(5372) Allen Bradley Controller Card 22DJ4-4000 On/Off for 4000 Series Sensors

(5373) Stegmann Encoder DG60D 10-30 VDC 200 Puls/Rev

(5377) Honeywell Analog Output Redundancy Board 51304355-125

(5378) Fanuc Automation Control Module A20B-2900-036