NEC FC-9821X工業(yè)工廠計算機(jī)
RS485串行端口一個滿載的PQM配有三個串行端口。COM1是PQM后端的RS485端口，通常用作系統(tǒng)的主要通信接口。COM2也是一個后置RS485端口，可用于數(shù)據(jù)收集、打印報告或問題分析，而不會干擾主通信接口。COM3是一個前面板RS232端口，可用于使用EnerVista PQM設(shè)置軟件進(jìn)行設(shè)定點編程或記錄。串行端口提供PQM與遠(yuǎn)程計算機(jī)、PLC或分布式控制系統(tǒng)（DCS）之間的通信功能。在單個通信信道上，多達(dá)32個PQM可以與24 AWG絞合屏蔽雙絞線菊花鏈在一起。合適的導(dǎo)線應(yīng)具有120Ω的特性阻抗（如Belden#9841）。這些電線應(yīng)遠(yuǎn)離高功率交流線路和其他電噪聲源。通信線路的總長度不應(yīng)超過4000英尺，以確?？煽窟\行。正確的極性對通信端口的工作至關(guān)重要。
RS485 Serial Ports A fully loaded PQM is equipped with three serial ports. COM1 is a RS485 port available at the rear terminals of the PQM which is normally used as the main communications interface to the system. COM2, which is also a rear RS485 port, can be used for data collection, printing reports, or problem analysis without disturbing the main communications interface. COM3 is a front panel RS232 port that can be used for setpoint programming or recording using the EnerVista PQM Setup software.A serial port provides communication capabilities between the PQM and a remote computer, PLC, or distributed control system (DCS). Up to thirty-two PQMs can be daisy chained together with 24 AWG stranded, shielded, twisted-pair wire on a single communication channel. Suitable wire should have a characteristic impedance of 120 Ω (such as Belden #9841). These wires should be routed away from high power AC lines and other sources of electrical noise. The total length of the communications wiring should not exceed 4000 feet for reliable operation. Correct polarity is essential for the communications port to operate.
轉(zhuǎn)載請附上此鏈接：http://m.wzljsf.com/
