Protection for signal conditioners

[NetNathan]

Okay forum control geeks ... Do you fuse each signal conditioner or a group?
I have a job that has 25 signal conditioners, some for voltage (0-80V = 4-20mA) and some for current (0-5A = 4-20mA).

Should I fuse the 24VDC power to each one or maybe groups of 5 or 1 fuse for all?

This seems debatable, I have never had a signal conditioner go bad as far as blowing a fuse.

 

[thingstodo]

Okay forum control geeks ... Do you fuse each signal conditioner or a group?
I have a job that has 25 signal conditioners, some for voltage (0-80V = 4-20mA) and some for current (0-5A = 4-20mA).

Should I fuse the 24VDC power to each one or maybe groups of 5 or 1 fuse for all?

This seems debatable, I have never had a signal conditioner go bad as far as blowing a fuse.

We have lost current sensors that output direct to 4-20 mA. The current signal just goes away. So it's reported as under-range

Is there a 'natural' split? Like your isolators are fed into an analog card with 8 channels? or 4?

I would likely use a power supply that detects short circuit and shuts itself off. The Devicenet power supplies all seem to do that. Then use a mini breaker big enough for all 25 signal conditioners.

Unless there a reason to use different 24V power supplies? Do you need one production stream to stay running if the other has a device trip?

 

[NetNathan]

All signal conditioners are on the same 24VDC power.

The 24VDC power supply has short circuit protection (Phoenix Contact QUINT) and is dedicated to the circuit for the signal conditioners and the Acromag Analog Input modules only...after that it is Profinet to PLC.

The signal conditioners are converting the voltage and current signals to 4-20mA for 2 16pt AI modules (Acromag XT1233) that have Profinet comms to GE RX3i PLC.
The Acromag AI modules are fused.

 

[Bit_Bucket_07]

All signal conditioners are on the same 24VDC power.

The 24VDC power supply has short circuit protection (Phoenix Contact QUINT) and is dedicated to the circuit for the signal conditioners and the Acromag Analog Input modules only...after that it is Profinet to PLC.

The signal conditioners are converting the voltage and current signals to 4-20mA for 2 16pt AI modules (Acromag XT1233) that have Profinet comms to GE RX3i PLC.
The Acromag AI modules are fused.

If your PS goes to 0V on short circuit, then you won't be blowing any fuses anyway. At best, they'll be convenience disconnects so that you could work on one instrument while leaving the others powered up. Knife switch terminal blocks would work as well as fusible terminal blocks for that.