Rosemount DP Transmitter Grounding
Rosemount DP Transmitter Grounding
(OP)
Quick question for the grounding experts. Why does Rosemount supply grounding screws with all of their 2-wire (DC) transmitters when in the thousands that I've either installed, calibrated, or commissioned, I have never seen a ground wire pulled and/or terminated.
Thanks!
Thanks!





RE: Rosemount DP Transmitter Grounding
But, given typical installations, the transmitter housing is alredy grounded to much better grounds than the PE will ever be. So that terminal is usually/sometimes left unconnected.
But, I am not sure if that is good practice - or even legal...
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Rosemount DP Transmitter Grounding
RE: Rosemount DP Transmitter Grounding
A two-wire DP transmitter uses a 4-20 mA loop, which is floating. If one of the wires wasn't connected you would not be able to even calibrate the thing.
The ground terminal is for safety grounding and should not influence measurement accuracy.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Rosemount DP Transmitter Grounding
RE: Rosemount DP Transmitter Grounding
Basically, what I found is that Rosemount provides the transient voltage grounding screw (internal/external) for local code purposes. What they do caution against is running that ground wire in the same conduit as the 4-20mA loop as an errant lightning strike could cause enough transient voltage on the 4-20mA loop wiring to damage the transmitter.
RE: Rosemount DP Transmitter Grounding
RE: Rosemount DP Transmitter Grounding
Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Rosemount DP Transmitter Grounding
I've been working in the I&C Field for years in Petrochemical, Refining, Power, and Water/WasteWater. I'm no salesperson....but, maybe its time for a switch...I could use the raise...
Like I said above, I've never seen a ground wire landed on the internal or external ground screw.
Just to clear up any confusion, lets keep in mind I'm not talking about the *Shield* wire thats normally cut back, wrapped around the single conductors, and taped off in the transmitter housing. I'm actually talking about a ground conductor, not the shield provided in a twisted shielded pair.
I found the info right in the manual provided by Rosemount.
http:
Page 2-43
"NOTE
The transient protection terminal block does not provide transient protection
unless the electronics case is properly grounded. Do not run the transient
protection ground wire with field wiring because the transient protector ground
wire may carry excessive current if a lightening strike occurs. Grounding the
electronics case using a threaded conduit connection may not provide
sufficient ground."
Thats out of the manual for the 3095. during a search I believe I found it in the 3051 manual as well.
RE: Rosemount DP Transmitter Grounding
But, the truth is that there could be some technical background to that. Not inside a factory building. But in an oil refinery or some other wide-spread plant where wires pick up transients during a thunderstorm.
They do so by induction or influence (if not properly screened) or potential difference between two parts of the plant and a direct hit is not needed to cause problems. Nothing survives a direct hit. No matter how your wiring is connected or where you put your wires.
But, to answer the OP, Transmitters and controllers are usually screwed down to grounded things like panels, cabinets, valves, tubes etcetera. So the extra grounding that the ground terminal provides is of little practical importance. But code probably requires a wire to be connected to it.
Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Rosemount DP Transmitter Grounding
Thanks for all the replies!