Fuse Monitor Alarm infi-90 DCS


Thread Starter


Dear Friends
Greetings of the day

i appreciate if someone share his experience related to DCS Infi-90.
why we jumper on termination unit of digital input slave termination unit TU-NTDI01 with slave card IMDSI02 and describe it as fuse monitor?

when and why this input signal changes its state? in our case it is always one and when it goes zero for few seconds it also trigger at least four or five inputs from 12 inputs. Physically jumper is ok and fuse also ok, but it looks internal circuitry of TU open this contact in response of certain condition.

thanks in advance

The Net90/Infi-90/Symphony digital input modules do not have embedded fuse monitoring to develop system alarms. The architecture is so flexible in nature (can have 24VDC, 48VDC, 120VAC, and 125VDC inputs on the same module in the latest version) and as a result fuse monitoring is handled externally on an as needed basis. All fuse monitor inputs use digital input channels just like process inputs.

The flexible design allows four combinations of power use:

1. Use all external power, no system power
2. Allocate some or all inputs to system power E1/F1.
3. Allocate some or all inputs to system power E2/F2.
4. Allocate some inputs to system power E1/F1 and others to E2/F2.

Depending on the configuration, it is good practice and therefore common design to monitor the E1 and/or E2 system power after the F1/F2 fuses depending on which ones are used, on a per digital input module basis.

I'll use the example where one or more digital inputs use both E1/F1 and E2/F2 system power.

Appropriately located jumpers and dip shunts will route the fused power back to a digital input, with the appropriate connection on the dip shunt back to the voltate reference. It is possible also to eliminate the need for a physical jumper with an appropriately configured dip shunt.

With this arrangement, the digital inputs monitoring fused system power should ALWAYS be a logic one (true) state, except when there is a problem. The problems could be a blown fuse, or loss of power upstream of the fuse.

Naturally, if there is a power interruption, the other digital inputs monitoring process conditions will also go to a logic zero state (for those that are normally logic one) due to the same loss of power condition.

If the power loss is short and comes back without intervention, then you do not have a blown fuse condition - you will have to look for loose wiring or power source quality issues.
Dear Mr. John

Thank you very much for your sharing

In our case all contacts are system powered 24 DC and powered through E1/F1. now the confusion is this, which input is short/ground or taking more leakage current during the moment. cable testing with ground or megger test shows all input cables ok and Slave card+ TU (IMDSI02+NTDI01) already replaced with new one.

My focus is to locate the source of interruption because all alarms of 5 inputs appear and reset with in 10 seconds at same time. it is bit difficult to trace and these inputs are very critical like surge protection, flame and machine vibrations.

if i keep open the jumper of fuse monitor what will happen? fuse will blown? or something else?

Plz give your expert opinion how to locate and rectify the fault?

Rather than chase the fuse details, let's go back and very clearly describe the problem.

Can you describe in detail the problem, while answering some key questions?

1. Is the problem focused on only one termination unit/input module?

2. At what approximate cycle, or intervals does the problem occur?

3. Have you looked at the system and process alarm and event lists prior to and during the event, to determine if there is anything common between more than one event? If so what is it (or what are they)?

4. How many input channels are wired and configured? Are inputs 8 and 16 used?

5. Before the events, which channels are at a logic one (closed) state, and which are zero?

6. During the event, do all logic one (closed) inputs open?

7. During the event, does the slave status change state (if monitored?) If not monitored, it should be (they all should be).

8. Does the fuse require replacement to recover from the event?

Once we have these basics out of the way we can take the next step to the root cause.

Dear Mr. John

Thanks for your help.

Problem occurs at only one TU-Slave card where 11 modules are installed on MMU of 12 slots in the row.

Problem occurred on 4th August-2014, 11th August-2014 and 14th August-2014.

4th and 11th august alarm sequence is same.

16 channels are configured and only 14 are wired while 8th input is not used and 16th input is used for fuse monitor.

Before event 7-channels are zero and 7-chaanels are one.

after event 12 inputs status goes to zero for 10 seconds and reset.

Does not require fuse replacement.

Last performed actions:

Less critical input channel 7 cables removed from TU for observation on 14th august

IKTU01 Cable also swapped for observation

Tightening of cables from JB and TU

Today is 26th and problem not appeared yet but my focus is to pin point the issue.

if you share your e-mail address i will provide you the signal

drawing while my email address is [email protected]