與PLC控制系統(tǒng)連接的各類信號傳輸線，除了傳輸有效的各類信息之外，總會有外部干擾信號侵入。此干擾主要有兩種途徑：一是通過變送器供電電源或共用信號儀表的供電電源串入的電網干擾，這往往被忽視；二是信號線受空間電磁輻射感應的干擾，即信號線上的外部感應干擾，這是很嚴重的。由信號引入干擾會引起I/O信號工作異常和測量精度大大降低，嚴重時將引起元器件損傷。對于隔離性能差的系統(tǒng)，還將導致信號間互相干擾，引起共地系統(tǒng)總線回流，造成邏輯數據變化、誤動和死機。PLC控制系統(tǒng)因信號引入干擾造成I/O模件損壞數相當嚴重，由此引起系統(tǒng)故障的情況也很多。來自接地系統(tǒng)混亂時的干擾接地是提高電子設備電磁兼容性（EMC）的有效手段之一。正確的接地，既能抑制電磁干擾的影響，又能抑制設備向外發(fā)出干擾；而錯誤的接地，反而會引入嚴重的干擾信號，使PLC系統(tǒng)將無法正常工作。PLC控制系統(tǒng)的地線包括系統(tǒng)地、屏蔽地、交流地和保護地等。接地系統(tǒng)混亂對PLC系統(tǒng)的干擾主要是各個接地點電位分布不均，不同接地點間存在地電位差，引起地環(huán)路電流，影響系統(tǒng)正常工作。例如電纜屏蔽層必須一點接地，如果電纜屏蔽層兩端A、B都接地，就存在地電位差，有電流流過屏蔽層，當發(fā)生異常狀態(tài)如雷擊時，地線電流將更大。此外，屏蔽層、接地線和大地有可能構成閉合環(huán)路，在變化磁場的作用下，屏蔽層內有會出現感應電流，通過屏蔽層與芯線之間的耦合，干擾信號回路。若系統(tǒng)地與其它接地處理混亂，所產生的地環(huán)流就可能在地線上產生不等電位分布，影響PLC內邏輯電路和模擬電路的正常工作。PLC工作的邏輯電壓干擾容限較低，邏輯地電位的分布干擾容易影響PLC的邏輯運算和數據存貯，造成數據混亂、程序跑飛或死機。模擬地電位的分布將導致測量精度下降，引起對信號測控的嚴重失真和誤動作。

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NetApp FAS6030-A 24.2TB Cluster w/ 56 450GB 15K FC

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Netapp FAS6030C w/48x DS14MK2 300GB X267A-R5 201TB!!

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Rack NetApp 14x DS14MK4 w/14x 300GB 15K X279A-R5 58.8TB

Rack NetApp 14x DS14MK4 w/14x 300GB 15K X279A-R5 58.8TB

Rack NetApp 14x DS14MK4 w/14x 300GB 15K X279A-R5 58.8TB

NetApp FAS3020C 10 Transferable Licenses 168TB X269A-R5

Full Rack Netapp 14x DS14MK2AT 1TB X269A-R5 168TB!!

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NetApp FAS3070C w/12x DS14MK2-AT 14x 1TB X269A-R5 168TB

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Netapp FAS6030C 24x DS14MK2AT 750GB X268A 252TB FAS6030

Netapp FAS6030C w/48x DS14MK2-AT 500GB 336TB!!! FAS6030

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Netapp FAS6030 w/12x DS14MK2-AT 1TB X269A-R5 168TB!!!!

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Netapp FAS6030C 24x DS14MK2 300GB X276A 100TB FAS6030

NetApp FAS3070-A Cluster 17TB 112x 144GB FC 10K REF

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NetApp FAS3070-A Cluster 28TB 56 500GB SATA 7.2K

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NetApp FAS3050C CIFS ISCSI CLUSTER MULTISTORE 24TB 15K

Network Appliance NETAPP FAS3040C with 8 Licenses

Dell, NetApp DS14MK2-AT FAS 3050 Storage System 56TB

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NetApp FAS3050C CIFS NFS ISCSI SNAP MOVE CLUSTER 24TB

Lot of 20 Netapp DS14 MK2 w/14x 300GB 10K X276A 84TB!!

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專業(yè)銷售進口DCS? PLC系統(tǒng)備件模塊