CR4® - The Engineer's Place for News and Discussion®


Previous in Forum: What is It?   Next in Forum: Email - Perplexing Experience
Close
Close
Close
9 comments
Anonymous Poster #1

4-20 mA Surge Protector

02/17/2017 4:14 PM

Hello everyone,

Does anybody know about a surge protector for 4-20mA signals that can easily be switched from 2-wire to 4-wire and vice versa without rewiring any field wire or internal wiring in a control panel?

Thanks for the help!

Reply
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Comments rated to be "almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
Guru
Hobbies - DIY Welding - Wannabeabettawelda

Join Date: May 2007
Location: Annapolis, Maryland
Posts: 4179
Good Answers: 235
#1

Re: 4-20 mA Surge Protector

02/17/2017 7:47 PM

I'm confused. How can you have a 4-20mA process loop change from 2-wire to 4-wire without rewiring 'something'? You either have a loop powered device or an externally powered device.

Reply Score 1 for Good Answer
Guru

Join Date: Aug 2007
Location: Earth - I think.
Posts: 2028
Good Answers: 158
#2
In reply to #1

Re: 4-20 mA Surge Protector

02/18/2017 12:44 PM

Not to mention the fact, that regardless of whether it is 2-wire or 4-wire instrument, there are really only 2 wires physically connecting the field instrument to the DCS/PLC.

i.e. This should be a non-issue.

__________________
TANSTAAFL (If you don't know what that means, Google it - yourself)
Reply
Anonymous Poster #1
#4
In reply to #1

Re: 4-20 mA Surge Protector

02/18/2017 6:59 PM

You're right. Let me explain a little bit further, I've seen some system integrators use proprietary surge protectors like these. Basically, you have a dedicated power supply for your instrument's signals feeding all your surge protectors and each SP has a jumper o dip-switch that let you use or not the power supply for your 2-wire instruments. You don't have to rewire anything in your panel but rather choose the right position of the sp's jumper. I just want to know if somebody has come across something like that and also that is commercially available. I appreciate your comments!

Reply
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain, and now disconnecting as Little England and Wales (not too sure about Wales bit, either). Kettle's on.
Posts: 26709
Good Answers: 701
#7
In reply to #4

Re: 4-20 mA Surge Protector

02/19/2017 4:45 PM

So, pick up the phone and talk to the <...some system integrators...> that actually use the things. Sheesh!

__________________
"Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Reply
Anonymous Poster #1
#8
In reply to #7

Re: 4-20 mA Surge Protector

02/20/2017 9:18 AM

I have tried. Like I said, it is proprietary and they don't sell them commercially, they use them in their own panels. If you know of a integrator that sell them I would appreciate their contact information so I can call them like you are suggesting. Thank you for your reply.

Reply
Guru
United Kingdom - Member - Not a New Member Hobbies - Musician - New Member Hobbies - Fishing - New Member

Join Date: May 2006
Location: Reading, Berkshire, UK. Going under cover.
Posts: 9555
Good Answers: 456
#3

Re: 4-20 mA Surge Protector

02/18/2017 5:17 PM

At the panel, connect surge protection devices between supply and 0v, +ve side of loop and 0v and -ve side of loop and 0v. Then it doesn't matter whether you use loop-powered (2 wire) or active (4 wire) sensors, everything will be protected.

__________________
"Love justice, you who rule the world" - Dante Alighieri
Reply
Power-User

Join Date: Nov 2009
Posts: 289
Good Answers: 55
#5

Re: 4-20 mA Surge Protector

02/18/2017 7:09 PM

The people who make and sell this stuff should be able to tell you.

Phoenix Contact has some surge stuff for 4-20mA

https://www.phoenixcontact.com/assets/downloads_ed/local_us/web_dwl_technical_info/2554A.pdf

Another forum thread with commentary:
http://www.control.com/thread/968448839

Reply
Guru
New Zealand - Member - Kiwi Popular Science - Weaponology - New Member Engineering Fields - Power Engineering - New Member Engineering Fields - Electrical Engineering - New Member

Join Date: Sep 2006
Location: Auckland, New Zealand
Posts: 8461
Good Answers: 350
#6

Re: 4-20 mA Surge Protector

02/19/2017 2:07 PM

I am not aware of any products (they possibly exist, I have never come across an application that has needed them), but you can add individual transient voltage surge suppressor devices that are designed for low voltage data lines, like TVS, Avalanche or possibly Zener diodes.

If voltage surges are a problem with your application (or your spec calls for them) you need fast, low breakdown voltage protective devices to protect the 4-20mA signal equipment. MOVs and gas discharge tubes are likely not going to be low enough voltage or have a fast enough response.

UPDATE: I just had a quick look online and they exist

Link

__________________
jack of all trades
Reply
Anonymous Poster #1
#9
In reply to #6

Re: 4-20 mA Surge Protector

02/20/2017 9:26 AM

Thanks for the reply, I have used Dehn in the past and they are good surge protectors but they don't have one with the feature I'm describing, I also checked with Phoenix Contact and they don't have them either. Again, thanks for the help.

Reply
Reply to Forum Thread 9 comments
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Comments rated to be "almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
Copy to Clipboard

Users who posted comments:

Anonymous Poster (3); Brave Sir Robin (1); Carl_E (1); jack of all trades (1); JohnDG (1); Kilowatt0 (1); PWSlack (1)

Previous in Forum: What is It?   Next in Forum: Email - Perplexing Experience

Advertisement