Am I missing something here? Is the right answer here? If so can someone explain?

[cnowak]

A 4-20mA single CT has a max range of 150 amp what is the amps at 14mA?


140A

105A

150A

90A

[rofo42]

A 4-20mA single CT has a max range of 150 amp what is the amps at 14mA?


140A

105A

150A

90A
I'm seeing 105A.

[cnowak]

I'm seeing 105A.

Can you please explain how you got that?

[jrm5116]

I think this is what they're looking for.

20mA is represented by 150A so 14mA/20mA * 150 = 105A...

This would mean 4mA would be equivalent to 30A and nothing under that value would pick up. I'm not positive if this is correct, but it seams to line up. If 4mA is equivalent to 0A then I'm not sure, because that answer doesn't seem to be there or I was doing that incorrectly.

[rofo42]

Can you please explain how you got that?

I found it the unconventional way I'm sure and might not be correct.

150 / .020 = 7500

.014 * 7500 = 105

Like the poster above noted, 4mA would be 30A.

[Kalbi_Rob]

I think this is what they're looking for.

20mA is represented by 150A so 14mA/20mA * 150 = 105A...

This would mean 4mA would be equivalent to 30A and nothing under that value would pick up. I'm not positive if this is correct, but it seams to line up. If 4mA is equivalent to 0A then I'm not sure, because that answer doesn't seem to be there or I was doing that incorrectly.

I think ya'll have a slight conceptual misunderstanding of how transducers work. Transducer typically output range of 4mA to 20mA. That means 4mA equals the low range minimum, and 20mA is high range maximum. For a 0-150A CT, 4mA is equal to 0A and 20mA is equal to 150A.

So, I've always just made my range 0mA to 16mA, with my reading minus 4.

So, at 14mA, my calculation would be (10mA*150A)/16mA = 93.75, so my guess would be the answer of 90A due the possibility of inaccurate.

Not sure if this question is the best example to work off of, did you get this from the question bank? Might be one to bring up to the administrators.

To check my work I use calculators similar to this one:

https://www.sensorsone.com/4-20ma-to-linear-measurement-converter/?iunit=mA&irdg=13.9733333333&ilo=4&ihi=20&ounit=A&olo=0&ohi=150

[rofo42]

I think ya'll have a slight conceptual misunderstanding of how transducers work. Transducer typically output range of 4mA to 20mA. That means 4mA equals the low range minimum, and 20mA is high range maximum. For a 0-150A CT, 4mA is equal to 0A and 20mA is equal to 150A.

So, I've always just made my range 0mA to 16mA, with my reading minus 4.

So, at 14mA, my calculation would be (10mA*150A)/16mA = 93.75, so my guess would be the answer of 90A due the possibility of inaccurate.

Not sure if this question is the best example to work off of, did you get this from the question bank? Might be one to bring up to the administrators.

To check my work I use calculators similar to this one:

https://www.sensorsone.com/4-20ma-to-linear-measurement-converter/?iunit=mA&irdg=13.9733333333&ilo=4&ihi=20&ounit=A&olo=0&ohi=150

Interesting. Are transducers and CTs commonly assumed to be the same? It didn't feel like I was doing it correctly 🙃Thanks.

Edit: the mA output should have made it obvious.

[Kalbi_Rob]

Interesting. Are transducers and CTs commonly assumed to be the same? It didn't feel like I was doing it correctly 🙃Thanks.

Edit: the mA output should have made it obvious.

Transducers are made for various applications, such as: voltage, current, power, pf, etc.

The outputs can be different also, typically you will find 4mA - 20mA or mV. This output is typically used on older systems using analog meters, etc. It is very common in PLC applications.

So, the application above, the CT converts your system current down to 0-5A signal (extra calculation that wasn't needed), which is fed to the transducer and converted to a 4mA to 20mA signal. Transducers must also be adjusted using the zero (null setting x ->) and span (range setting |<- x ->|) screws.

WARNING: I haven't touched a transducer in years and going of my hazy memory.

[jrm5116]

I think ya'll have a slight conceptual misunderstanding of how transducers work. Transducer typically output range of 4mA to 20mA. That means 4mA equals the low range minimum, and 20mA is high range maximum. For a 0-150A CT, 4mA is equal to 0A and 20mA is equal to 150A.

So, I've always just made my range 0mA to 16mA, with my reading minus 4.

So, at 14mA, my calculation would be (10mA*150A)/16mA = 93.75, so my guess would be the answer of 90A due the possibility of inaccurate.

Not sure if this question is the best example to work off of, did you get this from the question bank? Might be one to bring up to the administrators.

To check my work I use calculators similar to this one:

https://www.sensorsone.com/4-20ma-to-linear-measurement-converter/?iunit=mA&irdg=13.9733333333&ilo=4&ihi=20&ounit=A&olo=0&ohi=150

That was my original answer as well. Since that wasn't an answer option I assumed it wasn't what they were looking for. I'd be curious to see if anyone knows what they actually intended with this question.

[Izeldeen]

A 4-20mA single CT has a max range of 150 amp what is the amps at 14mA?


140A

105A

150A

90A

20/150=14/x
x=105amp

[cnowak]

I was trying it the way you described because that's what I had been taught. And like we have figured out it is not an answer choice. And yes it was from the pool of questions in my NETA 2 Practice Test. Unfortunately I think the question is ignoring the 4-20mA and treating it like a 0-20mA because of the answer choices available.


I think ya'll have a slight conceptual misunderstanding of how transducers work. Transducer typically output range of 4mA to 20mA. That means 4mA equals the low range minimum, and 20mA is high range maximum. For a 0-150A CT, 4mA is equal to 0A and 20mA is equal to 150A.

So, I've always just made my range 0mA to 16mA, with my reading minus 4.

So, at 14mA, my calculation would be (10mA*150A)/16mA = 93.75, so my guess would be the answer of 90A due the possibility of inaccurate.

Not sure if this question is the best example to work off of, did you get this from the question bank? Might be one to bring up to the administrators.

To check my work I use calculators similar to this one:

https://www.sensorsone.com/4-20ma-to-linear-measurement-converter/?iunit=mA&irdg=13.9733333333&ilo=4&ihi=20&ounit=A&olo=0&ohi=150

[Izeldeen]

I was trying it the way you described because that's what I had been taught. And like we have figured out it is not an answer choice. And yes it was from the pool of questions in my NETA 2 Practice Test. Unfortunately I think the question is ignoring the 4-20mA and treating it like a 0-20mA because of the answer choices available.

same answer.

[bec51392]

Sooo testguy says 105 is right, are we voting this one wrong?

[testguy]

Sooo testguy says 105 is right, are we voting this one wrong?

Thanks for reporting, this question will be updated. See answer explination by Kalbi_Rob: https://testguy.net/threads/8410-Am-I-missing-something-here-Is-the-right-answer-here-If-so-can-someone-explain?p=14735#post14735

[bec51392]

I took my NETA 3 this week and this question ended up on my test! Thanks to you guys I think its fair to say I got it right. Thanks everyone!

[BruceG400]

A 4-20mA single CT has a max range of 150 amp what is the amps at 14mA?


140A

105A

150A

90A


105A
150 divided by 20 is 7.5
That would be 7.5mA on secondary per 1 amp on primary.
at 14mA on secondary (14 x 7.5 = 105) that would be 105 amp on primary.
Ignore the 4 in the 4-20mA range as that is just a pickup for accuracy. Even using on 16 or 17 for the span of the range of the 4-20mA, the answer would be 123A or 131A, which is not an option, so the A per mA ratio is based on the 150 divided by 20 and ignores the lower limit of 4.

[BruceG400]

I think ya'll have a slight conceptual misunderstanding of how transducers work. Transducer typically output range of 4mA to 20mA. That means 4mA equals the low range minimum, and 20mA is high range maximum. For a 0-150A CT, 4mA is equal to 0A and 20mA is equal to 150A.

So, I've always just made my range 0mA to 16mA, with my reading minus 4.

So, at 14mA, my calculation would be (10mA*150A)/16mA = 93.75, so my guess would be the answer of 90A due the possibility of inaccurate.

Not sure if this question is the best example to work off of, did you get this from the question bank? Might be one to bring up to the administrators.

To check my work I use calculators similar to this one:

https://www.sensorsone.com/4-20ma-to-linear-measurement-converter/?iunit=mA&irdg=13.9733333333&ilo=4&ihi=20&ounit=A&olo=0&ohi=150


Using that calculator with 30 as the Low Limit, it calculates the primary current to be 105A.

[Jamo33]

Using that calculator with 30 as the Low Limit, it calculates the primary current to be 105A.


If this is a transducer, then at 0 amps the output will be 4mA.
So, rather than the lower limit being 30A by calculating 150A/20mA as the max outputs, we are instead calculating 150A/(20-4) to adjust for the 4mA offset. So it is instead 150/16=9.375mA per primary Amp
Then use this reading and multiply it by the corrected secondary reading ie (14mA-4mA)=10

9.375*10=93.75A