I think what he is saying is that in an otherwise healthy 4-20mA circuit, you could have some other external factor which causes an unsafe situation that would render the circuit not intrinsically safe. So he is recommending the added protective circuits.
(perhaps here we are saying the same thing)?

It seems we are, and the only disagreement seems to be on the correction required to clear it up. I do believe changing “are” to “are not” is sufficient. But of course, any written text is likely to be susceptible to improvement, so perhaps it could be made more clear if reworded. I don’t find it confusing, though, so I am not sure where the improvement is needed aside from the typo correction.

 

It seems we are, and the only disagreement seems to be on the correction required to clear it up. I do believe changing “are” to “are not” is sufficient. But of course, any written text is likely to be susceptible to improvement, so perhaps it could be made more clear if reworded. I don’t find it confusing, though, so I am not sure where the improvement is needed aside from the typo correction.

What about this:
However, the normally modest voltage and current values within a healthy 4-20 mA loop circuit aren't low enough for that circuit to be considered intrinsically safe if there is a device or wiring fault. In order to be intrinsically safe, the circuit’s voltage and current levels must be limited even in the event of device or wiring faults.

 

In order to be intrinsically safe, the circuit’s voltage and current levels must be limited even in the event of device or wiring faults.

Hi Mack.
I would say most responsible designers would include those common sense safety features in their product designs.

In the Marine 20mA current products, I have designed, the above safety features were part of the product specification.
E

BTW: any feedback from Admin.?

 

Hi Mack.
I would say most responsible designers would include those common sense safety features in their product designs.

In the Marine 20mA current products, I have designed, the above safety features were part of the product specification.
E

BTW: any feedback from Admin.?

It usually takes many years of experience and mistakes (or years of training) to be aware of the potential issues. My only hope is that I can gain the benefit of that thru training and other's good advice and experience rather than thru mistakes. Thanks for the info.

 

What about this:
However, the normally modest voltage and current values within a healthy 4-20 mA loop circuit aren't low enough for that circuit to be considered intrinsically safe if there is a device or wiring fault. In order to be intrinsically safe, the circuit’s voltage and current levels must be limited even in the event of device or wiring faults.

I don't think that is good writing because it requires the reader to incorporate the end of the sentence to understand it. If I was inclined to rewrite in that way, I would say something like:

"The normally modest voltage and current of a healthy 4-20ma loop are not, on their own, sufficient to consider it intrinsically safe because it lacks protection against a fault causing those values to increase beyond the prescribed limits."

 

I don't think that is good writing because it requires the reader to incorporate the end of the sentence to understand it. If I was inclined to rewrite in that way, I would say something like:

"The normally modest voltage and current of a healthy 4-20ma loop are not, on their own, sufficient to consider it intrinsically safe because it lacks protection against a fault causing those values to increase beyond the prescribed limits."

Yes, that works for me.
I am not adverse to asking people to read an entire sentence before they understand its entire meaning tho.
However, I think your wording has an overall better ring to it.
Thanks, I believe this is solved. Just waiting on confirmation now.

 

I seem to have missed something here
were was the original quote from ?

 

I seem to have missed something here
were was the original quote from ?

Take a look at the TS' first post.

 

If you visit this link: http://www.ibiblio.org/kuphaldt/socratic/sinst/
look for:
Lessons In Industrial Instrumentation textbook [PDF]

You should find the info on p, 2611 of "Lessons In Industrial Instrumentation"

 

If you visit this link: http://www.ibiblio.org/kuphaldt/socratic/sinst/
look for:
Lessons In Industrial Instrumentation textbook [PDF]

You should find the info on p, 2611 of "Lessons In Industrial Instrumentation"
View attachment 258344

Thank you

Are you going to take this up with the author ?

 

It was my understanding that this was the forum to do that.

 

It was my understanding that this was the forum to do that.

Unless the author is logged into this forum
or this book is written by the forum
I'm not certain how or if there is feedback direct to author or publisher

I'd suggest that you contact the author or publisher,
they might have an errata section on there web site,