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Old December 3rd, 2019, 12:48 PM   #16
danw
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Quote:
Originally Posted by GaryS View Post
I would be concerned about the length of wire with any analog signal
If he does this as 2 wire, loop powered 4-20mA with a single power supply in the receiver panel (the conventional manner), then a 400 foot run is nothing to 4-20mA. Absolutely no signal loss.



I've seen 4-20mA cable runs of over a mile (1.6Km) at the mills that have run for years with no problem at all.


Conventional 4-20mA is VERY robust.


I have no idea if the 2 supply thing will even work, but to me it isn't worth bothering with because loop powered, 2 wire, passive 4-20mA transmitters were designed to work with a remote power supply at the receiver.



2 wire cabling runs from receiver panel to the field is the prime driver for 4-20mA; the wire break fault detection at 0mA is just a side benefit.
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Old December 3rd, 2019, 01:21 PM   #17
m_turk
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Quote:
Originally Posted by danw View Post
If he does this as 2 wire, loop powered 4-20mA with a single power supply in the receiver panel (the conventional manner), then a 400 foot run is nothing to 4-20mA. Absolutely no signal loss.



I've seen 4-20mA cable runs of over a mile (1.6Km) at the mills that have run for years with no problem at all.


Conventional 4-20mA is VERY robust.


I have no idea if the 2 supply thing will even work, but to me it isn't worth bothering with because loop powered, 2 wire, passive 4-20mA transmitters were designed to work with a remote power supply at the receiver.



2 wire cabling runs from receiver panel to the field is the prime driver for 4-20mA; the wire break fault detection at 0mA is just a side benefit.
+1
Until 300m and if on the same "earth" I don't even think about it as an issue..
If it is another building or longer I'd consider some separators or protection, barriers but 100m is nothing...

And, I'd use the plc power supply too if possible, less possible problems..
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Old December 3rd, 2019, 02:02 PM   #18
janner_10
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It's a bit of a mess before it gets off the ground. Wouldn't some form of remote IO be a better solution.
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Old December 3rd, 2019, 03:23 PM   #19
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It's a bit of a mess before it gets off the ground. Wouldn't some form of remote IO be a better solution.
The OP needs a shielded, twisted pair cable for each transmitter. In my world, that isn't messy, it's conventional and any instrument guy with a DVM can troubleshoot it.

Yes, he could do remote I/O, but for how many signals/transmitters? There's a point where ROI comes into play.
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Old December 5th, 2019, 12:51 AM   #20
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You have analogue signals 100m apart, I would say you've past the point of getting remote IO already, simply on future proofing and trouble shooting grounds alone.
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