关于信号线路电阻值的问题!

maleis

我做的北大青鸟维护系统现在出现一个问题,系统遭雷击关闭!某一段信号线路用万用表蜂鸣档测量没有短路,但是用2M电阻档测量,就有800多阻值(正常情况应该是2条信号线间电阻超过2兆,2M档根本测不到),现在每拆掉一个探头或模块,阻值就增大一点,只要能测到小于2M的值应该都不正常,我的办法就是全部拆除后端设备查看到底是哪个设备的信号端子被击穿,造成信号线间阻值减小!

各位有不同意见可以探讨下,共同学习提高!

jinrenyu007

哎呀，这个问题啊是阻值的并联问题了，你用蜂鸣档没有短路就是没有短路了，用2M测量的话，你说的大于2M是没有负载的情况下了，你的负载越多他的总阻值就会越小，因为R=1/R1+1/R2+.....1/Rn  了。所以你不用拆了，直接上设备了就好了。还有，每种报警厂家都会有短路保护器的，等你接上主机看短路保护器有没有动作就好了。

易修师傅

现在报警主机上报了怎样的故障？


如果线路阻抗过小或短路隔离摸块会动作，如线路没问题，某个部损坏主机上应该会报故障。

maleis

现在不止报故障的问题了!

有些设备问题是用蜂鸣档及2M档根本测不出来,只有用二极管档位才测出来是被击穿,把这部分设备送厂家维修,他们根本不测二极管,说没问题,又给退回来,装上这些设备,回路就报故障,回路电压是正常的,但是回路板散热IC却烫手,拆掉被击穿的设备就OK.

你们遇到过类似问题吗?

xx2006

我遇到过松江的手动报警按钮二极管被雷击穿过的事，主机回路板、主板被雷击坏了，修好安装上后主机报回路短路，开始以为是短路隔离器有问题，从隔离器下端量电阻很小，开始怀疑是手报有问题，好在就7、8个手报，拆到第2个手报时系统就好了。一般雷击时手报比模块和探测器容易坏。

liwenfei

你说的问题不对

一个编码设备直接测量就不会超个2M，线路满载8K左右

雷击后可能现场设备可能短路,设备阻值变低,正反两端阻值不相等,再就是只能用编码器测试,设备有问题都会引起回路故障

maleis

恩．楼上的高手，学习了，是满载时候阻值远低于２Ｍ，看了下说明书，大于５Ｋ都正常，事实是大于７－８Ｋ才正常！多谢各位高手！

但是那个二极管反向值问题是事实，刚刚遇到，也刚刚排除这个故障，用编码器可以测试出来的设备故障的方法我的意见不敢苟同，问题是查出的设备用编码器测试一切正常！

总之，多谢各位高手的批评指正及帮助！

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