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Discussion Starter · #1 ·
Just wondering how far others have had to go for a 4-20 mA device from a PLC and what wire size did you use? I've tried a couple of online calculators, but want to hear some real world experience. I'm trying to see if a mile on #18's will work? Or if paralelling wires would be a better option? We've paralleled for a DO to control a solenoid with no issues.
 

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I have gotten a mile if I switch the common on 24v DC and half wave DC. On #20 gauge.

Off the top of my head paralelling seems a bad idea, larger wire makes more sense.

Always tried to keep ma under a 100 feet. ( ~30 meters for my friends up north)

The other thing is how fast is the analog going to change value and how critical is it?

My experence with analog it is pretty slow.
 

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Electron Factory.Worker
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8-10k feet easy over 19 gauge comm cable.

19awg is approx 8ohms/thousand feet so
8*20000=160

160ohms * .02A is only 3.2v of drop.

The biggest issue is lightning strikes/high voltage power ground faults. Likes to blow stuff up.

The runs these days are shorter because the electronics are less expensive than running all that copper everywhere.
 

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Discussion Starter · #5 ·
I've got a rough distance, and it is about 4.02 km (13,190 feet). The existing control wiring is an older phone cable, maybe 20 ga wiring (?), maybe 22. A new cable would be a tough sell, as it is all underground. That being said there have been a few conductor failures over the years, so a new cable may become a necessity.

We're testing out some surge protectors on a couple of pressure transmitters that were prone to being lightning magnets. Those analog cables are in the 100' length. So far there's only been one storm go through and there was no issues, but it's tough to troubleshoot lightning when there's no lightning. And not many are keen in taking a wire from the POCO and trying to strike the area to simulate it. Yes I'm joking on that option.
 

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Discussion Starter · #6 ·

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Discussion Starter · #7 ·
I have gotten a mile if I switch the common on 24v DC and half wave DC. On #20 gauge.

Off the top of my head paralelling seems a bad idea, larger wire makes more sense.

Always tried to keep ma under a 100 feet. ( ~30 meters for my friends up north)

The other thing is how fast is the analog going to change value and how critical is it?

My experence with analog it is pretty slow.
I've typically seen several hundred feet of cable between a PLC and an analog transmitter with no issues.
It would be on a pipeline pressure transmitter.
 

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Electron Factory.Worker
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I've got a rough distance, and it is about 4.02 km (13,190 feet). The existing control wiring is an older phone cable, maybe 20 ga wiring (?), maybe 22. A new cable would be a tough sell, as it is all underground. That being said there have been a few conductor failures over the years, so a new cable may become a necessity.

We're testing out some surge protectors on a couple of pressure transmitters that were prone to being lightning magnets. Those analog cables are in the 100' length. So far there's only been one storm go through and there was no issues, but it's tough to troubleshoot lightning when there's no lightning. And not many are keen in taking a wire from the POCO and trying to strike the area to simulate it. Yes I'm joking on that option.
Short the pair on one end and measure the resistance at the other. That should tell you everything you need to know. If you know the distance pretty well than you can probably determine the wire gauge as well.

You could also put your loop calibrator on the end and take the loop for a test drive to the PLC as well to verify that it will work.
 

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Would you be able to utilize a WIFI signal?
Next week I'm trying out a product, for a remote camera, which is supposed to function at 6 miles line of sight.
It can be programmed as a WAP.
My salesman at ADI claims they so far haven't had any complaints with a few years of selling this. Also good to -40. Perfect for those warm Alberta winters lol
Fluid Gas Font Cylinder Gadget
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Discussion Starter · #11 ·
Would you be able to utilize a WIFI signal?
Next week I'm trying out a product, for a remote camera, which is supposed to function at 6 miles line of sight.
It can be programmed as a WAP.
My salesman at ADI claims they so far haven't had any complaints with a few years of selling this. Also good to -40. Perfect for those warm Alberta winters lol
View attachment 167630 ķ
There's no cell coverage or line of sight between the PLC and the transmitter.
 

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Would you be able to utilize a WIFI signal?
Next week I'm trying out a product, for a remote camera, which is supposed to function at 6 miles line of sight.
It can be programmed as a WAP.
My salesman at ADI claims they so far haven't had any complaints with a few years of selling this. Also good to -40. Perfect for those warm Alberta winters lol
View attachment 167630 ķ

good luck especially if you have any pine trees nearby.
 

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I understand the NO G land concept.

Have you considered dedicated industrial radios?

or

I was always impressed with their customer service back in the days of the "protocol conversion".
 

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It is definitely going to depend on the specs of the sensor. The excitation for the sensor is a straightforward voltage drop calculation, if that's coming from a mile away as well as the sensor loop. The power you'll have to supply to the sensor loop is going to depend on the output load range of the sensor. I don't think it will be doable a problem if you can get in spec. The analog phone system works on 48VDC and powers thousands of 20ma - 30ma loops over crappy cable 20awg and smaller all day and night for over a hundred years.
 

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I put a transmitter on about 2k of old ug phone cable and then around 2k of 18/2 belden a while back, not real keen on the plan but it did work. I did the test drive with my 789 process meter to check it, did have to find a good pair in the phone cable first. Put a loop isolator at the RTU as insurance. I'd have liked the idea better if I had 100% shield continuity back to the cabinet but there was at least one poor splice in the phone cable in the past.
 

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We run 2000 feet downhole plus 100-200 feet to PLC with our well level transmitters. The only time we have issues are when they change one out that has smaller wire, and was fed from the display. The voltage drop gets too great for the display to power it, we just change to PLC power and it works good. Some of our older panel used the local display for loop power, we don't do that anymore.
 
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