15340667322
热门搜索：
正确选择接地点，完善接地系统
接地的目的通常有两个，其一为了安全，其二是为了抑制干扰。完善的接地系统是PLC控制系统抗电磁干扰的重要措施之一。
系统接地方式有：浮地方式、直接接地方式和电容接地三种方式。对PLC控制系统而言，它属高速低电平控制装置，应采用直接接地方式。由于信号电缆分布电容和输入装置滤波等的影响，装置之间的信号交换频率一般都低于1MHz，所以PLC控制系统接地线采用一点接地和串联一点接地方式。集中布置的PLC系统适于并联一点接地方式，各装置的柜体中心接地点以单独的接地线引向接地较。如果装置间距较大，应采用串联一点接地方式。用一根大截面铜母线（或绝缘电缆）连接各装置的柜体中心接地点，然后将接地母线直接连接接地较。接地线采用截面大于22mm2的铜导线，总母线使用截面大于60mm2的铜排。接地较的接地电阻小于2Ω，接地较好埋在距建筑物10~15m远处，而且PLC系统接地点必须与强电设备接地点相距10m以上。信号源接地时，屏蔽层应在信号侧接地；不接地时，应在PLC侧接地；信号线中间有接头时，屏蔽层应牢固连接并进行绝缘处理，一定要避免多点接地；多个测点信号的屏蔽双绞线与多芯对绞总屏电缆连接时，各屏蔽层应相互连接好，并经绝缘处理。选择适当的接地处单点接点。
PLC控制系统中的干扰是一个十分复杂的问题，因此在抗干扰设计中应综合考虑各方面的因素，合理有效地抑制抗干扰，对有些干扰情况还需做具体分析，采取对症下药的方法，才能够使PLC控制系统正常工作。
下面我们着重介绍三菱公司的FX2N系列产品的一些编程元件及其功能。
NEW JUNIPER SSG-140-SH Juniper SSG 140 Security Gateway
Juniper DX-3200-SLB-SSL-N-2C USED
Juniper Netscreen NS-ISG-1000 NS-ISG-4FE 2GB Advanced
1 year warranty - we buy and sell networking equipment
Enlarge
Juniper P-4CHDS3-QPP
Juniper RE-400-256 for M10i/M7i Warranty
Juniper Networks J4350 Wired Router
Juniper Networks M40 Internet Backbone Router
Juniper PE-1GE-LH PE 1GE LH
Expedited shipping available
Juniper PB-1GE-LX-B
Expedited shipping available
NEW Juniper PB-4OC3-SON-SMIR 4-port SONET SDH OC-3,STM1
One-day shipping available
Juniper I-1OC48-SON-SFP + FPC-E GF
Juniper PB-1CHOC12SMIR-QPP PIC M40e M320 M640 T320 T640
Juniper Networks (J2320-JB-SC) J-series Services Rou...
Buy this product now!
One-day shipping available
Juniper P-1GE-LH PIC for M20/M40 Warranty
Juniper PB-1OC12-ATM2-SMIR M160 T320 M320 T640 Router
One-day shipping available
Juniper M20BASE-AC RE-600-2048 SSB 4 PICS FPC AC PWR GF
JUNIPER NETWORKS M7i WIRED ROUTER
Juniper Archer Field PC & Carlson SurvCE 2.0 Software
Agilestar - XFP-10G-E-OC192-IR2 - Juniper - New in Box
Agilestar - XFP-10G-E-OC192-IR2 - For Juniper Networks
Juniper PE-1GE-LH M7i M10i M5 M10
Juniper NS-SA-3010A NetScreen Secure Access 3000
Juniper SRX-GP-24GE-POE - SRX-GP-24GE with POE
World's Largest Reseller of Used Foundry/Brocade/Cisco
Expedited shipping available
Juniper M20BASE-AC RE333/768 P-1GE-SX P-4OC3-SON-SMIR
90 Day Warranty - Free Shipping!
Juniper M10BASE-DC-E M10 Router AC Power Available
90 Day Hardware Warranty - Free Shipping!
Juniper NS-5200 w/ NS-5000-M & NS-5000-2G24T 5000-24FE
Save big!! 1-YR warranty, CALL 415-483-1189
One-day shipping available
Juniper Router w/ RE-333-256 and 2 AC Power M10-BASE-AC
NEW Juniper PE-1OC12-SON-SMIR PIC for M5 M7i M10 M10i
90 Day Warranty - Free Shipping!
Juniper M10BASE-AC Chassis w/ RE-333-768 + AC Power
1 Year Warranty - No Reasonable Offers Ever Refused!
Juniper M10 Base AC w/ RE-333-768 and (1) AC
Juniper M5 Base AC w/ RE-333-768 and (1) AC
Juniper PB-4DS3-ATM2 Module 4 Port DS3 GF
NEW JUNIPER XFP-10GE-SR Juniper 10GBase-SR Interface Mo
NEW JUNIPER SRX240B Juniper SRX240 Service Gateway - 4
JUNIPER EX-XFP-10GE-ER : JUNIPER ORIGINAL W/ WARRANTY
Juniper M10BASE-DC Chassis w/ RE-333-768 + DC Power
1 Year Warranty - No Reasonable Offers Ever Refused!
Juniper Archer Field PC & XF101 Sub-Meter GPS Kit
Juniper J4350-JB-SC Router GF
*New Sealed* JUNIPER EX4200-24T 24-port 10/100/1000Base
Juniper PE-1GE-LH Gigabit Eth PIC, LH Optics M7i M10i
JUNIPER NETWORKS P-ML-128 MULTILINK SERVICES REFURB
TESTED 90 DAY WARRANTY
Juniper PIC PE 2DS3,DS3 for M7i,M10i non-qpp 4chds3
Mint, Guaranteed PE 2DS3 card for Juniper M7i / M10i
JUNIPER NETWORKS PE-ML-128 MULTILINK SERVICES REFURB
TESTED 90 DAY WARRANTY
Juniper PB-4OC3-SON-SMIR 4-port SONET,SDH OC-3,STM1 PIC
90 Day Warranty - Free Shipping!
Juniper PB-4OC12-SON-SMIR 4 OC12 T640/M160/M40e Router
90 Day Hardware Warranty - Free Overnight Shipping!
Juniper Netscreen NS-500ES-GB2-AC Advanced Firewall
100VSYS! - 90 Day Warranty - Free Shipping!
Juniper SSB-E-16-M20 System Switch Board M20 16m DRAM