描述
从定时和计数控制上看，电器控制系统采用时间继电器的延时动作进行时间控制，时间继电器的延时时间易受环境温度和温度变化的影响，定时精度不高。而PLC采用半导体集成电路作定时器，时钟脉冲由晶体振荡器产生，精度高，定时范围宽，用户可根据需要在程序中设定定时值，修改方便，不受环境的影响，且PLC具有计数功能，而电器控制系统一般不具备计数功能。
NEW NATIONAL INSTRUMENTS PCI 232/485 8CH W/ CABLE
NATIONAL INSTRUMENTS AT-GPIB/TNT ASSY. 181830E-01 488.2
National Instruments BNC-2095 32 BNC connector
NATIONAL INSTRUMENTS GPIB-120A BUS EXPANDER/ISOLATOR
National Instruments SH48-48-A Shielded Cable 183229-01
NI National Instruments PCMCIA-232/4
National Instruments NI SH100-100-F FLEX 185095-02 2 m
Expedited shipping available
LOT NATIONAL INSTRUMENTS COMBO SOFTWARE DAQMX PXI SCXI
LOT 2 NATIONAL INSTRUMENTS 185196A CABLE 1M SH6868-8DB9
National Instruments SCX-1000 with 2x 1160 Modules
LOT NATIONAL INSTRUMENTS DAQ DAQMX SOFTWARE COMBO KIT
