Resistor Value Designations
Where can I find a web page that describes resistor value designations?
I have a schematic that calls out a resistor value of 4K74. Is this 4.7K? If so, what's the last "4" for? If it's not 4.7K, what is it? Further, there are values of 681R (681 ohms?), and 27K4 (? ohms). Did the Google thing but never found a formal chart. TIA Mike |
Resistor Value Designations
M wrote:
Where can I find a web page that describes resistor value designations? Did the Google thing but never found a formal chart. I can't imagine what search terms you might have used. http://66.102.9.104/search?q=Resistor.Values&num=100 My favorite page is #6 on the list: http://www.logwell.com/tech/componen...or_values.html For contrast: http://home.san.rr.com/nessengr/techdata/stdresval.html I have a schematic that calls out a resistor value of 4K74. Is this 4.7K? If so, what's the last "4" for? Looks like you didn't read it right or didn't type it right. Further, there are values of 681R (681 ohms?), and 27K4 (? ohms). http://groups.google.com/group/sci.electronics.misc/browse_frm/thread/f28ea9151766c021/3c5f53054583e8c5?q=saves-*-character-space+4k7-4700-*-*-*+*-*-*-*-decimal-point-doesn't-get-lost-when-documents-are-copied+zzz-zzz+crowded-schematics This thread was started by the guy who literally wrote the book: http://groups.google.com/group/sci.electronics.design/browse_frm/thread/6a4acf0ea03d2cfc?q=*-4k7-instead-of-4.7k+zzz+*-eliminating-them-altogether+qq-qq+less.chance.of.error+avoids.tiny.decimal.points +*-don't-reproduce-well+What's-wrong-with-decimal-points+the-European-scheme |
Resistor Value Designations
On Aug 6, 7:46 pm, "M" wrote:
Where can I find a web page that describes resistor value designations? I have a schematic that calls out a resistor value of 4K74. Is this 4.7K? If so, what's the last "4" for? If it's not 4.7K, what is it? Further, there are values of 681R (681 ohms?), and 27K4 (? ohms). Did the Google thing but never found a formal chart. TIA Mike The easiest way was to get it out of the DigiKey catalog -- like here http://dkc3.digikey.com/PDF/T072/1577-1582.pdf I would just print this out and keep it on the desk as a reference. In the CAD package I was using (jurassic CAD - Tango) instead of inserting a 'resistor' and then having to add the part number and pc footprint, I had each resistor as a separate entity by value so when I would insert a "27K4", the company part number, footprint and such were already buried in there ready to go. Made a BOM much easier. GG |
Resistor Value Designations
"M" wrote in message ... Where can I find a web page that describes resistor value designations? I have a schematic that calls out a resistor value of 4K74. Is this 4.7K? If so, what's the last "4" for? If it's not 4.7K, what is it? Further, there are values of 681R (681 ohms?), and 27K4 (? ohms). Did the Google thing but never found a formal chart. TIA Mike It's common in Europe to see the multiplier - in this case "k" - placed where the decimal point would be to avoid specks of fly**** on a page looking like a decimal point. So, a resistor designated 4k74 is the same as 4 point 74 k ohms. This may appear to be an 'odd' value of nearly, but not quite, the standard 4.7k (4k7) but may well be correct if the resistor is to be found in some precision circuit such as an opamp based filter with a specific cutoff frequency, or instrumentation amplifier requiring a precise gain figure. Such resistors are often calculated to this level of precision, and require to be made up from two or more values from one or several of the 'preferred' (standard) ranges of resitor values. 27k4 is 27.4k. "681" is unlikely to be an 'actual' value of 681 ohms. If it is a surface mount resistor that is being specified, it is probably 680 ohms, as these resistors are physically marked like this. It's the equivalent of marking them with coloured bands, but using the actual figures instead. Thus, the third digit is the equivalent of the multiplier band on a coloured stripe resistor. In your example 681 would mean "6" "8" (number of noughts) "1" or 680 ohms (may also be shown as "680R" using the system in the first paragraph) Just to confuse you, a resistor marked "680" in the surface mount scheme, will be 68 ohms, that's "6" "8" (number of noughts) "0" This could also be shown as 68R in the other scheme. A 0.47 ohm resistor would be shown as "0R47". A 100k resistor would be shown as "100k" (!!) and a 3.3 meg as "3M3" In surface mount they would be marked "104" and "335" respectively. Just for completeness, caps are often shown using the same schemes. So a cap shown on a schematic as "4n7" will be 4.7 nanofarads, or 4700pf. It will quite likely be physically marked using either resistor colour code stripes - yellow, purple, red - or the equivalent numbers in the same way as the surface mount resistors thus "472" Arfa |
Resistor Value Designations
M wrote: Where can I find a web page that describes resistor value designations? I have a schematic that calls out a resistor value of 4K74. Is this 4.7K? If so, what's the last "4" for? If it's not 4.7K, what is it? 4.74k Further, there are values of 681R (681 ohms?), and 27K4 (? ohms). Yes. E96 range values IIRC. Graham |
Resistor Value Designations
M wrote: Where can I find a web page that describes resistor value designations? I have a schematic that calls out a resistor value of 4K74. Is this 4.7K? If so, what's the last "4" for? If it's not 4.7K, what is it? 4.74k but if it's calling for a 5 or 10% tolerance part there's no need to use a close tolerance value. Graham |
Resistor Value Designations
On Mon, 6 Aug 2007 22:46:33 -0400, "M" wrote:
Where can I find a web page that describes resistor value designations? I have a schematic that calls out a resistor value of 4K74. Is this 4.7K? If so, what's the last "4" for? If it's not 4.7K, what is it? Further, there are values of 681R (681 ohms?), and 27K4 (? ohms). Did the Google thing but never found a formal chart. http://www.capgo.com/Resources/Measu...Resistors.html 4K74 is not a standard E96 or E128 value. If the schematic value of 4K74 (4,740 ohms) is correct, it has to be a special or a select on test resistor, but if the latter, it should be so designated. The closest E96 or E128 value is 4K75 (4,750 ohms) and if the circuit is so critical that it can't tolerate a standard value only 10 ohms away then I would question the designer's intention or design ability. |
Resistor Value Designations
Arfa Daily wrote:
"M" wrote in message ... Where can I find a web page that describes resistor value designations? I have a schematic that calls out a resistor value of 4K74. Is this 4.7K? If so, what's the last "4" for? If it's not 4.7K, what is it? Further, there are values of 681R (681 ohms?), and 27K4 (? ohms). Did the Google thing but never found a formal chart. TIA Mike It's common in Europe to see the multiplier - in this case "k" - placed where the decimal point would be to avoid specks of fly**** on a page looking like a decimal point. So, a resistor designated 4k74 is the same as 4 point 74 k ohms. This may appear to be an 'odd' value of nearly, but not quite, the standard 4.7k (4k7) but may well be correct if the resistor is to be found in some precision circuit such as an opamp based filter with a specific cutoff frequency, or instrumentation amplifier requiring a precise gain figure. Such resistors are often calculated to this level of precision, and require to be made up from two or more values from one or several of the 'preferred' (standard) ranges of resitor values. 27k4 is 27.4k. "681" is unlikely to be an 'actual' value of 681 ohms. If it is a surface mount resistor that is being specified, it is probably 680 ohms, as these resistors are physically marked like this. It's the equivalent of marking them with coloured bands, but using the actual figures instead. Thus, the third digit is the equivalent of the multiplier band on a coloured stripe resistor. In your example 681 would mean "6" "8" (number of noughts) "1" or 680 ohms (may also be shown as "680R" using the system in the first paragraph) Just to confuse you, a resistor marked "680" in the surface mount scheme, will be 68 ohms, that's "6" "8" (number of noughts) "0" This could also be shown as 68R in the other scheme. A 0.47 ohm resistor would be shown as "0R47". A 100k resistor would be shown as "100k" (!!) and a 3.3 meg as "3M3" In surface mount they would be marked "104" and "335" respectively. Just for completeness, caps are often shown using the same schemes. So a cap shown on a schematic as "4n7" will be 4.7 nanofarads, or 4700pf. It will quite likely be physically marked using either resistor colour code stripes - yellow, purple, red - or the equivalent numbers in the same way as the surface mount resistors thus "472" Arfa Here is a javascript for the two character codes on SMT capacitors: http://home.earthlink.net/~mike.terr.../SMD_caps.html I also have a three digit (5%) and four digit (1%) javascripts for resisitors, and the old three and six dot Micamold cpaacitors that I will make availible when I have more server space. -- Service to my country? Been there, Done that, and I've got my DD214 to prove it. Member of DAV #85. Michael A. Terrell Central Florida |
Resistor Value Designations
"M" wrote in message
... Where can I find a web page that describes resistor value designations? I have a schematic that calls out a resistor value of 4K74. Is this 4.7K? If so, what's the last "4" for? If it's not 4.7K, what is it? Further, there are values of 681R (681 ohms?), and 27K4 (? ohms). Did the Google thing but never found a formal chart. TIA Mike Thanks to all. Mike |
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