3500/61本特利3500/613500/61本特利3500/61

編程需要敢于實踐的信心

我曾經(jīng)教過一個學(xué)生學(xué)AutoCAD，我對她的*要求就是實踐。我告訴她：你隨便怎么操作，大不了一張圖重畫；zui壞的結(jié)果是系統(tǒng)崩潰，沒關(guān)系，系統(tǒng)重做，再來；只要電腦沒被砸了，怎么都行。兩年后，我再看到她做的CAD圖紙，也自嘆不如。

同樣道理，只有不斷地在PLC上運行這些指令，觀察運行的結(jié)果，才能弄清PLC指令的作用。很多初學(xué)者對PLC一臉的迷茫，往往是出于一種畏懼，擔(dān)心損壞設(shè)備。而這些畏懼是沒有任何道理的。仔細的閱讀手冊是非常重要的，但是僅靠讀書是成不了一個工程師的。更何況手冊上的內(nèi)容并非面面俱到。我在接觸到那些不熟悉的指令時，喜歡單獨編一個小程序，讓PLC運行。然后逐個修改條件，觀察運行的結(jié)果（MicroWin為用戶提供了非常好的監(jiān)控手段），反過來再重新理解手冊的描述，這樣就可以非常直觀的理解這些指令的作用和使用方法。不必擔(dān)心自己寫的程序會有什么問題，會影響PLC的正常工作。程序有沒有問題，只有讓PLC運行了才能發(fā)現(xiàn)。而發(fā)現(xiàn)問題并解決問題就是對自己能力的提高。撇開硬件操作不談，單就軟件來說，我還真沒有遇到過由于軟件問題而損壞PLC的事。在這里不必擔(dān)心繼電器電路接錯線可能造成的后果。所以，大膽的實踐是PLC編程的必由之路。

當(dāng)然，大膽實踐并不是野蠻操作，而是必須遵循必要的規(guī)范。還有一個要注意的，在程序未經(jīng)可靠性證實之前，千萬不要掛接負載，以免造成不必要的損失。數(shù)字量的輸出有LED顯示；而模擬量處理可以采用一些硬件或軟件模擬手段來解決。

鄭娟萍

廈門仲鑫航自動化設(shè)備有限公司  

編程需要有縝密的邏輯思維

編程本身就是一種邏輯思維過程。在高級語言中，使用zui多的是if then else、select這些條件判別語句，這就是邏輯中的因果關(guān)系。PLC程序就是由這些因果關(guān)系組成的：判別條件是否成立，進而決定執(zhí)行相應(yīng)的指令。zui初的PLC是用來替代繼電器邏輯電路的，所以繼承了繼電器電路以觸點作為觸發(fā)條件的描述方式。在PLC中，以虛擬觸點代替了繼電器的金屬觸點，而繼電器電路所表達的邏輯關(guān)系還是被完整的保留下來。即使引入了繼電器電路難以勝任的數(shù)值處理過程，PLC從根本上還是在執(zhí)行一個個因果關(guān)系。所以，理順對象的各個事件之間的邏輯關(guān)系，是編程之前必須精心做好的準備工作。我在接到一項任務(wù)后，*件事就是整理出一份邏輯關(guān)系圖，與用戶反復(fù)商討，取得用戶的認可，然后才真正進入程序的編寫過程。

Steren 200-033 RG6 Quad Shield Coaxial Cable Crimp F Connector (Pack of 100)

GEM Electronics 301-4 2-Piece BNC Crimp Connector (Pack of 37)

GEM Electronics 301-4 2-Piece BNC Crimp Connector (Pack of 33)

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Spears AX1J3 Bulkhead Tank Fitting 1/2"

tyco 179935-000 Multiple Entry Connection Kit

United Electric SD6213-27 Brass Bushing Kit

Electroline L660-1 Two-Hole EMT Strap (Box of 50)

Hubbell RACO 3410 2-1/2" Liquid-Tight Straight Connnector

Electroline L660-1 Two-Hole EMT Strap (Box of 49)

Walker Parkersburg Textron 500T Single Low Tension Plate

T&B Liquid-Tight 3/8" Fitting 90 Degree

T&B 3/8" Liquid-Tight Fitting 90 Degree

Appleton 3/8" Fitting 90 Degree

Appleton Fitting 3/8" 90 Degree

T&B Liquid-Tight 1" Fitting 90 Degree

T&B 1" Liquid-Tight Fitting 90 Degree

O-Z/Gedney 3/8" Liquid-Tight Fitting 45 Degree

O-Z/Gedney Liquid-Tight 3/8" Fitting 45 Degree

RACO 3/8" Liquid-Tight Fitting 45 Degree

RACO Liquid-Tight 3/8"  Fitting 45 Degree

T&B Liquid-Tight Fitting 3/4" Straight

T&B 3/4" Liquid-Tight Fitting Straight

Hubbell 3/4" Liquid-Tight Fitting Straight

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Appleton ST-100 Steel Connector 1" (Box of 6)

Appleton 3/4" Fitting 90 Degree

Appleton Fitting 3/4" 90 Degree

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Appleton 3/4" Fitting Straight

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O-Z/Gedney 4Q-938 Liquidtight Connector (Box of 13)

Bryant Electric, Inc. BDS85L Cable Grip 0.85"-1.0"

Hubbell 07310005 Kellems Grip 0.850"-1.000"

Hubbell 07310004 Kellems Grip 0.730"-0.850"

Hubbell 074-09-3403 Kellems Grip

Hubbell SR-040 Kellems Grip 0.40"-0.54"

T&B Cable Grip 1/2"

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Hubbell 073-03-1201 Kellems Grip 0.32"-0.43"

Hubbell 073-03-1204 Kellems Grip 0.73"-0.97"

Hubbell 1/2F1 Cord Connector

RACO 1 1/2" Liquid-Tight Fitting Straight

MW 3/4" Fitting 45 Degree

Appleton 1/2" Fitting 90 Degree

3/8" Liquid-Tight Fitting 45 Degree

Appleton 2" Fitting Straight

Appleton 1 1/2" Fitting 90 Degree

O-Z/Gedney 4Q-9125 1 1/4" Liquid-Tight Fitting 90 Degree

O-Z/Gedney 4Q-9100 1" Liquid-Tight Fitting 90 Degree

O-Z/Gedney 1/2" Liquid-Tight Fitting 45 Degree

RACO 3/4" Liquid-Tight Fitting 90 Degree

T&B 1 1/4" Liquid-Tight Fitting 90 Degree

Appleton 1" Fitting Straight

O-Z/Gedney 3/8" Liquid-Tight Fitting 90 Degree

O-Z/Gedney 3/4" Liquid-Tight Fitting 45 Degree

Appleton 1/2" Fitting 45 Degree

T&B 1 1/4" Fitting 90 Degree

MW 3/8" Liquid-Tight Fitting 45 Degree

Gould Efcor 1" Liquid-Tight Fitting 90 Degree

13-50 1/2" Liquid-Tight Fitting 45 Degree

1/2" Liquid-Tight Fitting 45 Degree

Ideal 3/4" Liquid-Tight Fitting 90 Degree

Hubbell 1/2F2 1/2" Liquid-Tight Fitting 90 Degree

Lapp Kabel 1/2-NPT 1/2" Skintop liquid-Tight Connector Straight Black

MW 3" Fitting Straight

Appleton 1 1/4" Fitting 45 Degree

12-75 3/4" Liquid-Tight Fitting 90 Degree

RACO 1" Liquid-Tight Fitting 90 Degree

Appleton 2" Fitting 90 Degree

T&B 2" Liquid-Tight Fitting 90 Degree

MW 1" Liquid-Tight Fitting Straight

O-Z/Gedney 1" Liquid-Tight Fitting Straight

Appleton EGS CG3138 Aluminum Cord Connector 3/8"

Steel City 1/2" Fitting Straight

Steel City 2 1/2" Fitting Straight

Appleton 3/4" Liquid-Tight Fitting Straight

ETP 3/8" Liquid-Tight Fitting 45 Degree

1" Fitting Straight

3/8" Liquid-Tight Fitting Straight

Halex 42-4 1 1/2" Fitting Straight

EMC LSC-18 1 1/4" Fitting Straight

T&B 1" Fitting 90 Degree

1 1/4" Liquid-Tight Fitting 90 Degree

Appleton 1 1/4" Fitting Straight

O-Z/Gedney 3/4" Liquid-Tight Fitting Straight

T&B 1 1/4" Liquid-Tight Fitting Straight

Madison IL 110 Armored Cable Connector 3/8"

T&B 1/2" Liquid-Tight Fitting 45 Degree

T&B 3/8" Liquid-Tight Fitting 45 Degree

Appleton ST-9038 Mall Iron Connector 3/8" (Box of 25)

RACO 3543 Liquid-Tight Connector 3/4" (Box of 12)

Efcor 13-50 Liquid Tite Connector 1/2" (Box of 8)

Appleton ST-90100 Mall Iron Connector 1" (Box of 7)

ETP LQ 3845 Liquid-Tight Connector 3/8" (Box of 12)

Madison IL 110 Armored Cable Connector 3/8" (Box of 50)

Amphenol 31-71000-RFX Crimp Plug

Bridgeport 412-DC2 Squeeze Connector 1 1/4" (Box of 10)

T&B Fittings 5343 Liquidtight Conduit Connector 8-Pack

Neer EGS LMM-11 Liquidtight Conduit Connector 20-Pack

Neer EGS GC-100 Screw-In Connector (Box of 25)

Neer EGS LMM-11 Liquidtight Conduit Connector 25-Pack

Appleton EGS CG3138 Aluminum Cord Connector (Box of 25)

O-Z/Gedney 4Q-938 Liquidtight Connector (Box of 15)

O-Z/Gedney 4Q-9125 Liquidtight Connector (Box of 5)

O-Z/Gedney 4Q-975 Liquidtight Connector (Box of 10)

O-Z/Gedney 4Q-75 Liquidtight Connector (Box of 10)

O-Z/Gedney 4Q-9100 Liquidtight Connector (Box of 3)

Appleton ST-9038 Liquidtight Connector (Box of 25)

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ILSCO D1112 Lug AU-0 1/0-14 AL9CU

Foster Manufacturing H6 Hydraulic Disconnect Coupling

Maska L-099X7/8 Half Coupling with L-099X3/4

Wiremold RPD-2CA Walkermed Electrical Raceway Bracket 9

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IR ARO 4TR75 CSN6-G Connector Strain Relief 16MM