描述
为使PLC能可靠工作，在硬件与软件两个方面PLC厂家都采取了很多措施，对一些特殊可靠要求的PLC，还有相应的特殊的措施，如热备、冗余等等。这在介绍PLC的特点时已作了叙述。可靠措施的目的是增加PLC平均故障间隔时间、MTBF（MeanTimeBetweenFailure）及减少PLC的平均修复时间、MTTR（MeanTimeToRepair），以提高PLC的有效度A（Availability）。
National Instruments AT-MXI 180775E-01 Interface Card
One-day shipping available
NATIONAL INSTRUMENTS VXIpc-745 PENTIUM VXI CONTROLLER
National Instruments High-Current 96 Ch PCI-6509
National Instruments Lab PC Assy 180835-01
2 pcs National Instruments PC-OPDIO-16 Interface Card
HV# National instruments VXI-MXI-2
National Instruments VXIpc-486 Model 566 182429M-20
National Instruments GPIB-SCSI-A Controller/Interface
2 available! IEEE 488/SCSI talk/listen/control/convert!
National Instruments NI PCI-6601 Card TESTED
National Instruments PCI DIO-32HS 183480E-01
National Instruments 182419C-02 SH6868 Cable 2 m
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