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I feel like an idiot asking this, but if the question is talking about 1k7 ohms of resistance, am i to believe that is the same as 1700 ohms?

Thanks ^^

James

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- #1

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I feel like an idiot asking this, but if the question is talking about 1k7 ohms of resistance, am i to believe that is the same as 1700 ohms?

Thanks ^^

James

- #2

stewartcs

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Yes.

I feel like an idiot asking this, but if the question is talking about 1k7 ohms of resistance, am i to believe that is the same as 1700 ohms?

Thanks ^^

James

CS

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What **is** this notation?

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stewartcs

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I think its crap. Doesn't really make sense to me, but I've seen it on spec sheets before (then they put = 1700 ohms beside it in parenthesis).Whatthis notation?is

CS

- #5

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From what you say, I presume it's done by engineers?I think its crap. Doesn't really make sense to me, but I've seen it on spec sheets before (then they put = 1700 ohms beside it in parenthesis).

CS

- #6

berkeman

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1k7 = 1.7k Ohms

1r7 = 1.7 Ohms

- #7

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Just one more question. You both say this is seen in various places, like spec sheets. Where else?

- #8

stewartcs

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That's a new one I haven't seen.1r7 = 1.7 Ohms

I suppose it may be to standardize the use of a comma (in Europe and other places) and a decimal in the US.

i.e. 1,7KOhms compared to 1.7KOhms.

- #9

berkeman

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It's common on European schematics. Either in application notes, or in customer schematics (in my work, I help out with customer design reviews fairly often, so I see a lot of schematics from all over the world).Just one more question. You both say this is seen in various places, like spec sheets. Where else?

Also, you'll sometimes see medium-size power resistors labeled with the 2R2 type of notation, if the value is written on the resistor (as opposed to using colored bands).

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ranger

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And that would mean...?

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I've seen the notation on the resistors themselves before.

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f95toli

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Which simply means a potentiometer with a maximum resistance of 4k7, i.e. 4700 Ohms

This notation is very common and often very conventient; especially when you have small letters on a component since you do not have to use a point since e.g. 1.7k can easily be misstaken for 17k. 1k7 and 17k look very different.

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> 1r7 = 1.7 Ohms

The k I've understood, but what is the 'r'? What would be 720 in this notation? (I don't know what they use for 100. But, suppose they use h, then it'll be 7h2, right)

- #15

berkeman

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I belive the R is just to show it is a resistor.> 1k7 = 1.7k Ohms

> 1r7 = 1.7 Ohms

The k I've understood, but what is the 'r'? What would be 720 in this notation? (I don't know what they use for 100. But, suppose they use h, then it'll be 7h2, right)

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And the 'k'?I belive the R is just to show it is a resistor.

- #17

berkeman

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Kilo = 1000And the 'k'?

Since there is no prefix for unity, they apparently picked the "R" for the resistor decimal point designator.

You will also see 47R for 47 Ohms, BTW.

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Resistors of several kilo ohm to a hundred kohm are very common, so they just say 2.2 k or 2k2, 100k etc.

They also use r as ohm, just because in electronic circuit schematics, resistors are often noted as R1, R2 etc...

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berkeman

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Why do you think it's a coincidence that the prefix k is used for kOhm? How many Ohms in a kOhm?The electronics use k with the meaning Kohm, not k as 1000x. It's just a coincidence.

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If not, they should use k, h, d as well. But i have never heard. I use to spend some time working with electronics circuits , electronics devices and the like, and we used the word k so often that we never thought it's x1000 (in fact it is), I just thought kohm is a unit which is used as often as ohm (even more).Why do you think it's a coincidence that the prefix k is used for kOhm? How many Ohms in a kOhm?

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(Oops, esteemed berkeman (a mentor in engineering) is on this thread! Didn't notice... )

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berkeman

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Nope, definitely not a coincidence. In electronics, we use MKS and the associated prefixes:If not, they should use k, h, d as well. But i have never heard. I use to spend some time working with electronics circuits , electronics devices and the like, and we used the word k so often that we never thought it's x1000 (in fact it is), I just thought kohm is a unit which is used as often as ohm (even more).

http://en.wikipedia.org/wiki/SI_prefix

Just as km = 1000m, kOhm = 1000 Ohms. Same deal.

It is also true that in engineering, we tend to stick with the prefixes that are powers of 3:

M = 10^6

k = 10^3

m =10^-3

[tex]\mu[/tex] = 10^-6

etc.

Like, if you turn on "Engineering Notation" on an HP calculator, you get scientific notation, but snapped to the nearest 3-power.

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OK, now I feel a bit reassured with the explanations.

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- #25

berkeman

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I disagree. We do math with those numbers all the time, often in our head. How can you calculate the LPF pole from R and C numbers, and not do the math on the prefixes too? The meaning of numerical prefixes never fades away -- they are part of the number itself.

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