DCS和PLC的设计原理区别较大，PLC是由摸仿原继电器控制原理发展起来的，70年代的PLC只有开关量逻辑控制，首先应用的是汽车制造行业。它以存储执行逻辑运算、顺序控制、定时、计数和运算等操作的指令；并通过数字输入和输出操作，来控制各类机械或生产过程。用户编制的控制程序表达了生产过程的工艺要求，并事先存入PLC的用户程序存储器中。运行时按存储程序的内容逐条执行，以完成工艺流程要求的操作。PLC的CPU内有指示程序步存储地址的程序计数器，在程序运行过程中，每执行一步该计数器自动加1，程序从起始步（步序号为零）起依次执行到最终步（通常为END指令），然后再返回起始步循环运算。PLC每完成一次循环操作所需的时间称为一个扫描周期。不同型号的PLC，循环扫描周期在1微秒到几十微秒之间。程序计数器这样的循环操作，这是DCS所没有的。

 

Nikon SMZ800 Stereomicroscop?e w/ SDC-240 Digital Camera

 

Seven Associates B-1A Induction Heating Unit

 

Dukane Lot of Qty 2 43A240 & Qty 1 Ultra 351 Auto-Trac

 

Tektronix VM700A opt;s 01 / 30 / 40 (Reduced!)

 

HP Agilent 5361A CW Microwave Counter, 10Hz to 20 GHz

 

CyberOptics MicroScan Laser Measure Unit

 

Tektronix VX4101A w/opt's 1A/1D (Reduced!)

 

EMCO 5101 Dual TEM Cell (Reduced!)

 

HP Agilent E4431B Digital RF Signal Generator (Reduced)

 

HP / Agilent 81110A (Reduced!)

 

HP 54825A Infinium Oscilloscope, 500MHz, 2GSa/s

 

Edwards High Vacuum Pump (Reduced)

 

Knight Tool Co. KTC-FT-62 Press

 

Forma Scientific 3908 Reach-In Incubator

 

HP 16453A Dielectric Material Test Fixture

 

Spirent TAS 4500C RF Channel Emulator

 

LeCroy DDA-120 1.0 GHz, 4 Channel 8GS/sec Oscilloscope

 

Solartron 1254 Frequency Response Analyzer (Reduced!)

 

Solartron/Schlu?mberger 1253 Gain Phase Analyzer.

 

Schaffner NSG 431 Electrostatic Discharge System

 

HP Agilent 83592C Sweeper Plug-In (Reduced!)

 

Olympus SZ6045 Stereo Imaging Microscope System

 

Blue M WSP-109B-3 Shock  ABB 3HAC020046-001 Chamber Oven

 

GCI DE1AC Air Conensing Chiller

 

Agilent N4483A

 

Koolant Koolers KV2000 Industrial Chiller

 

HP 35665A

 

ENI POWER SYSTEMS OEM-25 RF ABB 3HAC020046-001   Generator

 

HP Agilent 8591E Portable Spectrum Analyzer w/ opt 105

 

HP 4380A 500 MHz S-Parameter Test Set (Reduced!)

 

Tektronix A6909 Two Channel Isolator

 

EXFO FTB-300 w/opt's D2/M1/W1/N4 (Reduced!)

 

HP 16190A Perbance  ABB 3HAC020046-001   Test Kit, Complete

 

HP 16454A Magnetic Material Test Fixture, Complete

 

IRD 350 Vibration Analyzer (Reduced!)

 

Teledyne Taber V-5 150-B Electric Stiffness Tester

 

Budzar BTU Multi-Zone Electrically HeatedTemp. Unit

 

HP 8590D Opt. 003 Spectrum ABB 3HAC020046-001  Analyzer 1.8 GHz (Reduced)

 

Watson PS2-CB-2 Dual Position Payoff

 

Millipore Waters Quanta 4000E (Reduced)

 

HP Agilent 5183U Precision Digitizing Oscilloscope

 

Knight Tool Co. KTC-FT-54 Press

 

Ideal 3915-95 Guilotine, New, with Accessories

 

Tektronix VM700A opt's 01/ 40 (Reduced!)

 

Keithley 237 High Voltage ABB 3HAC020046-001  Source-Measure Unit (Reduced)

 

Union Special 35800 DR Felling Machine

 

Agilent E1439A VXI Digitizer Mod. (Reduced!)

 

Standard Environmental Systems Temperature Chamber