Fieldbus Communication Fail

How old is your is Remote I/O device connecting 8-12 segments? If you have spare, replace Remote I/O module.

Magnetic properties of chips(gates, decoder, encoder) where firmware is encoded is sensitive to temperature, memory (program, settings) deteriorate with time and with above or nearing operating temperature, that's why most of this type of devices you need to update firmware to experience maximum optimum efficiency from time to time.

When Remote I/O module is on busy traffic and hot, usually this faults happen. Is the area Remote I/O located cool or hot and humid? If hot, ventilate. If hot and humid, air condition.

Is this an intermittant problem or are you having comm fail all the time?

intermittent problem

main issue is how to solve this problem , cause what device need to change we have no idea ,

It may not be a device at all.

A ground fault (which is many times an intermittent issue) can cause the problem you describe.

A loose wiring connection can also cause what you are seeing.

A single device internally (intermittently) shorting to ground, or shorting the loop is also a possibility.

Unless you have taken a lightning strike or some other voltage surge, I think you can rule out the likelihood that all field devices failed at once.

We checked no ground fault, if it is then it will continue, some how itdisapper after while...segment become normal Assuming one device shorting internally how to catch ..?its fieldbus any technique

Depending on the fieldbus communication you are using (Ethernet, RS485, etc.) you might have a terminating resistor that is loose or missing.

I have several testers that utilize fieldbus communications. On 2 of the systems, the bus is parallel. One unit under test in an array of 8 with mis-wired, or shorted com wires will take out the entire array. When this happens disconnect all but one unit. If communication is restored, add another unit and verify communication again, repeat until a device stops communication, and troubleshoot the cable and socket wiring. Use the cable wiggle test as well. Intermittent shorts are probably your bandit.

Mr.mike it's intermittent happen ,and restore back communication, then it's our worry to find out root cause so it can be avoid in future Next we hook FBT-6 fieldbus monitoring device at mega block to monitor segment as I mentioned in my thread and result of fat-6 confusing us, it s show all device bad so during finding root cause why it happen ...? We have no clue which device or wire made problem...or making problem Any way we did that test to disconnect each device one by one and monitor at Fbt-6 device that can catch background culpit also, but no result so thinking as last option to change I/o module plus mega block that has already end terminators, plus change surge protectors , until we didn't do it but it's plan May be this will solve the problems and let avoid this to happen it again so at least our plant can be run smoothly

Check to see if the Tx and Rx wires on the FAT-6 device are reversed. Your diagnostic tool could be the problem. Inspect internal wiring to the power/com ports (if possible) on the devices on the com lines. Start with your diagnostic tool plugged into the bus alone, insure it works properly, then add one device at a time until the error appears. Divide and conquer!

I see you are using a Relcom FBT-6 - that tells us immediately that the "fieldbus" is in fact "Foundation Fieldbus." That is a common problem in the use of the term fieldbus in English. We use it for ALL busses, not just for FFB. You need to specify that this is indeed a FFB system or you will get answer such as you did - concerning any fieldbus, many of which do not apply to FFB.