描述
據(jù)長(zhǎng)期從事該項(xiàng)技術(shù)工作的同志講:①RS485通信短距離(800m以?xún)?nèi))的一般可使用無(wú)屏蔽的普通雙絞線②干擾較重時(shí)可使用帶屏蔽層的雙絞線(屏蔽層空懸/或只一端接地——要與“強(qiáng)電地”特別是“變頻器地”分開(kāi))③信號(hào)地一般空懸(不接線),如果接地不好反而不能正常通信。
多數(shù)網(wǎng)友也是以上這個(gè)意見(jiàn)。但也有部分網(wǎng)友認(rèn)為:應(yīng)將互聯(lián)設(shè)備共地;否則,如果接收端有較高共模輸入,就有可能損壞接收端器件。
多數(shù)情況下,連接RS-485通信鏈路時(shí)只需簡(jiǎn)單地用一對(duì)雙絞線將各個(gè)接口的“A”、“B”端分別連在一起,而將信號(hào)地空懸——這種連接方法在許多場(chǎng)合是能正常工作的,但應(yīng)注意以下兩個(gè)問(wèn)題:
(1)共模干擾問(wèn)題:RS-485接口采用差分方式接收輸入信號(hào),并不需要相對(duì)于某個(gè)參照點(diǎn)來(lái)檢測(cè)信號(hào),系統(tǒng)只需檢測(cè)兩根輸入線之間的電位差就可以了。但人們往往忽視了接收器有一定的共模電壓范圍,RS-485接收器共模電壓范圍為-7~+12V,只有滿(mǎn)足上述條件,整個(gè)網(wǎng)絡(luò)才能正常工作。當(dāng)通信線路中共模電壓超出該范圍時(shí)就會(huì)影響通信的穩(wěn)定可靠,甚至損壞接口。
(2)電磁輻射問(wèn)題:驅(qū)動(dòng)器輸出信號(hào)中的共模部分需要一個(gè)返回通道,如果沒(méi)有一個(gè)低阻的返回通道(信號(hào)地),就會(huì)以輻射的形式返回源端,整個(gè)總線就會(huì)像一個(gè)巨大的天線向外輻射電磁波。
歐美品牌停產(chǎn)的,常用的“PLC”備品備件
我司產(chǎn)品應(yīng)用于以下領(lǐng)域:
1,《發(fā)電廠DCS監(jiān)控系統(tǒng)》
2,《智能平鋼化爐系統(tǒng)制造》
3,《PLC可編程輸送控制系統(tǒng)》
4,《DCS集散控制系統(tǒng)》
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5,《智能型消防供水控制系統(tǒng)》
6,《化工廠藥液恒流量計(jì)算機(jī)控制系統(tǒng)》
7,《電氣控制系統(tǒng)》造紙,印染生產(chǎn)線,變電站綜合自動(dòng)化控制系列
本特利,英維思,伍德沃德,??怂共_、西屋、瑞恩、施耐德莫迪康、ABB、AB、西門(mén)子、摩托羅拉、GE發(fā)那科、安川、博世力士樂(lè),ACSO,力士樂(lè)等各大品牌的DCS系統(tǒng)配件,機(jī)器人系統(tǒng)配件,大型伺服系統(tǒng)備件。
Woodward 5461-651 Analog Input-8 Channel 4-20 mA
Woodward 5461-652 CURRENT INPUT
Woodward 5461-653
Woodward 5461-654 8 Ch RTD/input
Woodward 5461-655
Woodward 5461-656
Woodward 5461-659 DISCREET MODULE
Woodward 5461-661 Current Output Isolated-507(8 Channel)
Woodward 5461-768 Speed Control
Woodward 5461-769 Speed Reference
Woodward 5461-770 Speed Control
Woodward 5461-771 Speed Reference
Woodward 5461-772 Temp Control
Woodward 5461-773 SW Mode
Woodward 5461-774 Freq.Control
Woodward 5461-775 Amb.Bias Ramp
Woodward 5461-776 Accel.Schedule
Woodward 5461-777 Decel.Jump Rate
Woodward 5461-778 Liq.Final Driver
Woodward 5461-779 Fuel Transfer Card/Board
Woodward 5461-780 Gas Final Driver
Woodward 5461-781 Synchonizer
Woodward 5461-798 N1 Speed Control
Woodward 5461-880 RTD
Woodward 5461-892
Woodward 5461-944 Speed Control
Woodward 5461-975 Power Supply DCS 2 LV
Woodward 5461-975 Power Supply DCS 2 LV
Woodward 5462-017 DCS DIGITAL SPD SENSOR
Woodward 5462-085 FINAL DRIVER
Woodward 5462-117 POS TRANSDUCER
Woodward 5462-236
Woodward 5462-244 Liq.Final Driver
Woodward 5462-268 Mother Board for 505
Woodward 5462-292 Speed Sensor
Woodward 5462-336 Speed SENSOR
Woodward 5462-338 Power Aux Card
Woodward 5462-443 Fuel Transfer Card/Board
Woodward 5462-472
Woodward 5462-482
Woodward 5462-518 Speed SENSOR
Woodward 5462-519 Speed Control
Woodward 5462-520 Speed Reference
Woodward 5462-521 Power Sensor
Woodward 5462-522 Power Control
Woodward 5462-523 Power Refernce
Woodward 5462-524 Extraction Control
Woodward 5462-525 Pressure Prefernce
Woodward 5462-526 Ratio Limiter
Woodward 5462-527 Valve Ramp
Woodward 5462-528 Final Driver
Woodward 5462-529 Valve Ramp
Woodward 5462-530 Final Driver
Woodward 5462-531 Auxiliary
Woodward 5462-532 Pressure Channel
Woodward 5462-533 Power Prefernce
Woodward 5462-578 High Volt P/S
Woodward 5462-581
Woodward 5462-584 DCS Motherboard
Woodward 5462-651 ANALOG 8CH 4-20MA INPUT
Woodward 5462-718 SPEED SENSOR
Woodward 5462-749 COPROCESSOR
Woodward 5462-750 SEC.POWER SUPPLY
Woodward 5462-753
Woodward 5462-756
Woodward 5462-757 DISCRETE INPUT
Woodward 5462-758 DISCRETE OUTPUT
Woodward 5462-762 SIO Card
Woodward 5462-893 CPU Card
Woodward 5462-896
Woodward 5462-916 FTC-DCS II
Woodward 5462-917
Woodward 5462-944 DPS3/DT
Woodward 5462-948 T/C Card-8 Channel
Woodward 5462-966 Speed Sensor/Analog In
Woodward 5463-033
Woodward 5463-034 POWER AUX.N.C.
Woodward 5463-089 CPU
Woodward 5463-120 cpu module
Woodward 5463-124 Sio
Woodward 5463-127 SIO
Woodward 5463-140 Master CPU
Woodward 5463-141 Master CO CPU
Woodward 5463-143 Aux Memory
Woodward 5463-154 MODULE ASSY-509 DISCREET I/O
Woodward 5463-178 CPU Card
Woodward 5463-190
Woodward 5463-191
Woodward 5463-193
Woodward 5463-306 CPU Interface
Woodward 5463-306 Interface Module
Woodward 5463-338 RTD Input
Woodward 5463-372 FINAL DRVR
Woodward 5463-373 Analog Input Position Fdbk
Woodward 5463-375 Analog Input Position Fdbk
Woodward 5463-384 Analog Output
Woodward 5463-388 8CH RTD A/I














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