PLC是以微处理器为基础，综合了计算机技术、自动控制技术和通信技术，用面向控制过程面向用户的“自然语言”编程，适应工业环境，简单易懂、操作方便、可靠性高的新一代通用工业控制装置。PLC是在继电器顺序控制基础上发展起来的以微处理器为核心的通用自动控制装置。

可编程序控制器是一种数字运算操作电子系统，专为在工业环境下应用而设计。它采用了可编程序的存储器，用来在其内部存储执行逻辑运算、顺序控制、定时、计数和算术运算等操作指令，并通过数字的、模拟的输入和输出，控制各种类型的机械或生产过程。可编程序控制器及其有关的外围设备，都应按易于与工业控制系统形成一个整体、易于扩充其功能的原则设计。

PLC产品种类繁多，其规格和性能也各不相同。对于PLC，通常根据其结构形式的不同、功能的差异和I/O点数的多少等进行大致分类。

按结构形式分类

根据PLC的结构形式，可将PLC分为整体式和模块式两类。

整体式PLC

整体式PLC是将电源、CPU、I/O接口等部件都集中装在一个机箱内，如图所示。具有结构紧凑、体积小、价格低的特点。小型PLC一般采用这种整体式结构。整体式PLC由不同I/O点数的基本单元（又称主机）和扩展单元组成，基本单元内有CPU、I/O接口、与I/O扩展单元相连的扩展口以及与编程器或EPROM写入器相连的接口等；扩展单元内只有I/O和电源等，而没有CPU。基本单元和扩展单元之间一般用扁平电缆连接。整体式PLC一般还可配备特殊功能单元，如模拟量单元、位置控制单元等，使其功能得以扩展。

2）模块式PLC

模块式PLC将PLC的各组成部分分别做成若干个单独的模块，如CPU模块、I/O模块、电源模块（有的含在CPU模块中）以及各种功能模块。模块式PLC由框架或基板和各种模块组成，模块装在框架或基板的插座上，如图所示。这种模块式PLC的特点是配置灵活，可根据需要选配不同规模的系统，而且装配方便，便于扩展和维修。大、中型PLC一般采用模块式结构。

还有一些PLC将整体式和模块式的特点结合起来，构成所谓的叠装式PLC。叠装式PLC的CPU、电源、I/O接口等也是各自独立的模块，但它们之间是靠电缆进行连接的，并且各模块可以一层层地叠装。这样，不但系统可以灵活配置，还可做得体积小巧。

2.2.按功能分类

根据PLC的功能不同，可将PLC分为低档、中档、。

SWICHTEC INVENSYS ENERGY MAIN POWER BOARD 350-00079-01D DRG 21135 FOR R5800 ILPS
SWICHTEC INVENSYS ENERGY DRG 21592 CIRCUIT BOARD 350-00079-18B R5800 LCD DISPLAY
SWICHTEC INVENSYS ENERGY 350-0079-54C R5848-11 RECTIFIER CONNECTOR BOARD
STRONGARM Infrared Touchscreen Monitor SS NEMA4, WonderWare Invensys, InTouch?
SPARK MODULE, SM2 INVENSYS 120V. 3mA. A10006 - AMERICAN RANGE, BAKERS PRIDE 
SOME PLATES ARE DAMAGED SEE PICS FOR DETAILS
SM50 Intergy Invensys Supervisory Module
SIM-CCN GCM SIEBE Barber-Colman Invensys Carrier CCN Systems Integration Module
SIEBE PP-2446 PRESSURE TRANSDUCER BARBER COLMAN TAC INVENSYS ERIE
Siebe MSC-P-751 Environmental Controls Controller (Invensys?)
Siebe MSC-P1504-D Controller Lev-11 w/ AO & clock invensys robertshaw
Siebe MSC-NCM-D Controller invensys robertshaw
Siebe MSC-NCM Network Controller W/Modem MSCNCM Invensys
SIEBE INVENSYS MPC-8AI HVAC CONTROL, MULTI-PURPOSE CONTROLLER, ANALOG INPUT - US
SIEBE INVENSYS MPC-4A0 MULTI-PURPOSE CONTROLLER, ANALOG OUTPUT MODULE -  w/G
Siebe Invensys MK-2690-0-0-2 VKS-9263-203-4-35 Actuator Valve Stainless Steel
Siebe GCM SIM-York GCM-86000 York Talk Invensys TAC Network 8000
SIEBE BARBER COLMAN INVENSYS 1/2" NPT 3-WAY CONTROL BLEND VALVE VS-9313-201-4-4
SIEBE BARBER COLMAN INVENSYS 1/2" NPT 2-WAY CONTROL BLEND VALVE VK-9211-201-4-3
Siebe Barber Coleman Invensys VK-7213-201-4-01 Valve Assembly 1/2" reduced port
Sensus Invensys ICE 5/8" by 5/8" Water Meter SRII BRAND 
SEALED ! LAMBDA / INVENSYS POWER SUPPLY SE-500-3 SE5003
Scotsman Water Valve for CM250 120V 50/60hz 10W Invensys S-30 K-63916-12
Scotsman Water Valve 24V 60HZ 10W Invensys S-53N 283H11 K-67953
Scotsman Water Valve 24V 60HZ 10W INVENSYS K-76858
Scotsman 12-2548-01 Water Valve 24V 60HZ 10W Invensys 12-2548-01c
Schneider TAC Invensys Unit Ventilator Thermostat 2298-060  In Box
Schneider Invensys MP-495-0-2-2 Actuator 120V 50W .95A MP495022 50/60Hz
SCHNEIDER ELECTRIC, INVENSYS, TAC MN 150 LON CONTROLLER, SAT3 W/ROOFTOP PROFILE_
SCHNEIDER ELECTRIC, INVENSYS TAC MNL-V3R VAV CONTROLLER VAV MNL-V3RV2 PROFILE +_
Schneider Electric Invensys diverting relay 4-20 PSIG set point 2325-502
Safetran Invensys DC to DC Converter A53106 9000-53106-0001 Rev E3
RX-19-36 ROBERTSHAW / INVENSYS FRYER THERMOSTAT FOR MILLIVOLTS RX1936 RX 19 36
ROTAVAL STAINLESS FEEDER W/ INVENSYS(.90HP) MOTOR AND RADICON GEAR 
Robertshaw Invensys Valve Model #P2
Robertshaw Invensys Range Temperature Dial Knob #4590-004
ROBERTSHAW INVENSYS MG21-1126 PRESSURE CONTROL (R2-4-24KD)
ROBERTSHAW INVENSYS GIST 100 - 320°C GRIDDLE THERMOSTAT GAS VALVE WITH IGNITION
Robertshaw Invensys Gas Thermostat,for Vulcan,Garland,Southbend #BJWA 25PC1-536
Robertshaw Invensys Gas Thermostat,3/8" FPT, #46-347
Robertshaw Invensys FD0-3-02-54 Gas Thermostat Model FD0, 461128 GARLAND 
Robertshaw Invensys Electric Thermostat,25A,250VAC,Max 325*F, #KP-87-60
Robertshaw Invensys Electric Thermostat KXT-466-36 175 to 500 Degree
Robertshaw Invensys Electric Thermostat KX-289-30 100 to 450 Degree
Robertshaw Invensys Electric Thermostat 5110-052
Robertshaw Invensys Electric Oven Thermostat,30A,277VAC,Max Temp 325*F, #S-476-4
Robertshaw Invensys Electric Oven Thermostat,30A,277VAC,Max 450*F,#S-100-48
Robertshaw Invensys EA5-484-72 Electric Thermostat 180 degree max TST2528
Robertshaw Invensys Dual Solenoid Valve 3/8" FJT 120V #00497639-000G1
Robertshaw Invensys Add-On Stuffing Box Kit For Capillaries #4650-001
Robertshaw Invensys 9920I Thermostat Heat Pump
Robertshaw Invensys 9801I Thermostat Gas Electric Oil Heat Pump
Robertshaw Invensys 9560 Thermostat Heat Pump
ROBERTSHAW INVENSYS 9025i REMOTE OUTDOOR SENSOR
Robertshaw Invensys 9020I Remote Sensor Indoor Use
Robertshaw Invensys 8625 Thermostat Gas Electric Oil Heat Pump
Robertshaw Invensys 8425 Thermostat Gas Electric Oil Heat Pump
Robertshaw Invensys 8401 Thermostat Gas Electric Oil Heat Pump
Robertshaw Invensys 700-705 Energy Cut Off Switch HT3 E
RobertShaw Invensys 60 to 250*F Electric Thermostat Assembly #5300-615
Robertshaw Invensys 41-1402 Hot Surface Furnace Ignitor
Robertshaw Invensys 41-1090 Hot Surface Furnace Ignitor Universal Kit
ROBERTSHAW GAS FRYER THERMOSTAT RX-1-36 MILLIVOLTS INVENSYS CATERING SPARES
Robertshaw Electric Thermostat S-224-24 5300-014 5300-01D 400 Degree Invensys
Robertshaw 5459-074 Invensys Thermostat BNP-404-64 BTP-404-60 288153
Robertshaw 5225-06G High Limit 440F/227C Thermosta Invensys LCC770240000 
Robertshaw 4020-007 Gas Safety Valve FMDA Invensys
Robertshaw 4020-005 Gas Safety Valve FMDA Invensys
Robert Shaw Thermostat Invensys 100-550°F - D1320605900
Robert Shaw / Invensys Gard-Pak 2 Solid State Motor Protector 3433-046
Robert Shaw / Invensys Gard-Pak 2 Solid State Motor Protector 3433-037
RELAY ELECTRIC PNEUMATIC HVAC INVENSYS 2364-211 R471-1  IN THE BOX
Reduzierung Typ EATON (INVENSYS) Durchflussrate 5,5l/min Druckbereich 1-10bar
RECEIVER CONTROLLER 2341-501 INVENSYS  IN THE BOX
Ranco Invensys L30-83 Solenoid Coil 24 VDC for V1-V12 Reversing Valve Heat Pump
Ranco / Invensys A30-181, ADAPTABLE REFRIGERATOR CONTROL
R2948 Intergy Invensys Rectifier Module
PROV-GCM Proview Programmer/Operator Keypad MMI Invensys Barber-Colman Siebe TAC
Pneumodular Diverting Relay Robertshaw Or Invensys 2353-501  In The Box
Pneumodular Diverting Relay Robertshaw Or Invensys 2353-501  In The Box
Pitco P5047588,Vulcan 410837-1, Invensys GSA60301800, Gas Thermostat 66-1017 
PEM-1 Invensys Barber Colman Siebe Packaged Equipment Module
PEM 1 BARBER COLMAN SIEBE INVENSYS TAC NETWORK 8000 PEM-1 PEM1 _
PEM 1 - BARBER COLMAN NETWORK 8000, SIEBE, INVENSYS, TAC  Charity item
Peco/T.A.C./Invensys/Schneider Elec - TA-168-9 Manufacturer discontinued GREAT!!
P0917LYFPS40024 - FOXBORO - P0917LY FPS400-24 INVENSYS POWER SUPPLY 
ORIGINAL AC POWER ADAPTER FOR INVENSYS WONDERWARE KONTRON TUOC