在選擇方案時，應考慮盡量減少控制元件數、接點數和焊點數，以降低系統的失效率。采用可編程控制器（PC）來代替由繼電器等組成的控制柜可以提高系統的可靠性。在比較可編程序控制器和繼電器控制柜兩種方案時，除了購置價格以外，還應充分估計前者在提高可靠性、縮短開發周期和減小工作量以及節省維修時間等有利因素。為了減少系統的早期失效，機床制造廠可以對控制元件進行篩選，即使每臺元件在實際使用條件下連續工作一定次數，把失效產品排除，以減少裝到系統中的元件早期失效。元件進入耗損失效期以后，失效率將明顯上升。為了防止這種情況影響系統的可靠性，可以在有效壽命（或偶然故障期）將結束時，不管元件是否損壞，也進行更換。采用篩選和預防性更換，可以保證系統中的元件工作在偶然失效期內，在這個前提下才可以用元件的偶然失效率來計算系統的失效率。
提高可靠性的辦法，從根本上來說，應以現場失效調查和分析著手。和一般的產品設計和計算工作不同，可靠性設計不可能只通過理論和計算取得需要的結果，保證可靠性的程度取決于對使用現場實際發生的失效的了解（包括其深度和廣度）。實驗室試驗也是取得失效數據的一個方法，但由于試驗的內容、方法和條件限制，故只能是對現場使用情況的一個近似的模擬，它不可能代替使用現場失效情況的調查分析。脫離了現場條件的可靠性試驗是沒有實際意義的。
PLC可靠不等于PLC控制系統可靠。PLC控制系統比單獨的PLC復雜。系統復雜，出現故障的可能性就大，可靠性將降低。PLC控制系統不是PLC及其被控對象簡單地相加，而是兩者有機的結合。結合得好，才可靠。PLC控制系統也不等于PLC及其被控對象全面結合，只是與實施控制有關的才需要結合。
SQUARE D ATV18U09M2 ALTIVAR 1/2 HP DRIVE GOOD TAKEOUT
CONTROL TECHNOLOGY 2214 2 AXIS SERVO MODULE
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HEDLAND STAINLESS FLOWMETER 1/2'' FLOW RATE .3 TO 2.0
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AB6352-1 FAULT INDICATOR BOARD NEW SURPLUS
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KURZ MASS FLOW ELEMENT 450 FACTORY REMAN
TOSHIBA TOSVERT VT130G2 2025 TRANSISTOR INVERTER (2HP)
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MAZAK MITSUBISHI CIRCUIT BREAKER TYPE W-NV225-TA (NICE)
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CONTROL INSTRUMENTS PRB160 MAX 8000 CPU (NEW IN BOX)
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SIEMENS 6SE7090-0XX84-0KA0 WITH 6SE7090-0XX84-0FA0
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ACCURAY 64844-002 PRI PC BOARD EXCELLENT CONDITION
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ALLEN BRADLEY 1794-IB10X0B6 NEW FACTORY SEALED
ALLEN BRADLEY 1336S LANGUAGE MODULE 42336-602-41 NEW
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FANUC A860-0320-T111 PULSE CODER GOOD TAKE OFF
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NORTH AMERICAN SHAFT ENCODER H3107 (NEW!)
HARDMEIER CONTROL DV 1Q DRIVE CH-8307 NEW IN BOX
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YASKAWA JANCD-MM13 DF8203076/A0 MOTOMAN MEMORY BOARD
YASKAWA JANCD-HA03 REV.B MOTOMAN CARD *XLNT*
ALLEN BRADLEY 1398-DDM -009 SERVO DRIVE GOOD TAKEOUT
ALLEN BRADLEY 5431 8600 SERIES OASI BOARD
SIEMENS 500-5013 E-STAND BRAND NEW FACTORY SEALED
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ABB 5692-435-LX ENCODER (BRAND NEW)
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CONTROL INSTRUMENTS PRB160 MAX 8000 CPU (NEW IN BOX)
CONTROL INSTRUMENTS PRB172 PC BOARD MAX 8 CHANNELANALOG
SIEMENS 6SE7090-0XX84-0KA0 WITH 6SE7090-0XX84-0FA0
KOLLMORGEN PSR4/5A112 POWER SUPPLY GOOD CONDITION
