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Resistor Value in Journeyman Exam

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    #16
    Just in passing, if you work with these for any length of time, you get to recognise the values without having to work out what the colour values are.
    At a glance you can tell if it is 3.3kΩ or 33kΩ.
    It also helps that there a limited number of values. We generally used the E12 series. Twelve values and decade multiples thereof.

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      #17
      The multiplier is easy to remember how to implement if you think about the third band being the quantity of zeros that follow the first two digits.
      Master Electrician
      Electrical Contractor
      Richmond, VA

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        #18
        Originally posted by five.five-six View Post
        That chick Violet, she’s a hoe



        Bad Boys ____ our young girls but Violet gives willingly.

        Gold and silver are tolerances gold is 5% tolerance, silver is 10% tolerance and no band is 20% tolerance.
        That is the one I learned when in college. And though I don't find it to be all that offensive, that is probably the dirtiest phrase I ever heard come out of that particular instructor's mouth.

        They will delete the phrase I learned to remember the trigonometry functions if I posted that - but a lot of dirty stuff came out of that instructor's mouth - made things easy to remember though
        I live for today, I'm just a day behind.

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          #19
          Originally posted by kwired View Post
          That is the one I learned when in college. And though I don't find it to be all that offensive, that is probably the dirtiest phrase I ever heard come out of that particular instructor's mouth.

          They will delete the phrase I learned to remember the trigonometry functions if I posted that - but a lot of dirty stuff came out of that instructor's mouth - made things easy to remember though
          Sin is always an issue, and references to a tan gent get interesting too.

          Sent from my XT1585 using Tapatalk

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            #20
            Originally posted by kwired View Post
            That is the one I learned when in college. And though I don't find it to be all that offensive, that is probably the dirtiest phrase I ever heard come out of that particular instructor's mouth.

            They will delete the phrase I learned to remember the trigonometry functions if I posted that - but a lot of dirty stuff came out of that instructor's mouth - made things easy to remember though
            Indian Chief SOH CAH TOA??? Perhaps not Politically Correct...

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              #21
              Originally posted by five.five-six View Post

              Gold and silver are tolerances gold is 5% tolerance, silver is 10% tolerance and no band is 20% tolerance.
              Then there is the 1% which is white, Mil Spec or military grade.
              The 95% of people that you can't trust give the other 5% a bad name.

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                #22
                I wonder whether they intentionally manufacture resistors to such close tolerances, or they make them, measure them, and mark them according to the tolerance for which they qualify.
                Master Electrician
                Electrical Contractor
                Richmond, VA

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                  #23
                  Originally posted by LarryFine View Post
                  I wonder whether they intentionally manufacture resistors to such close tolerances, or they make them, measure them, and mark them according to the tolerance for which they qualify.
                  1% resistors are definitely manufactured differently. Among other things a different construction can be necessary to get a stability appropriate to the tolerance.
                  I would not be surprised if 5% and 10% resistors came off the same production line.
                  20% resistors might come off a different production line.

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                    #24
                    Originally posted by GoldDigger View Post
                    1% resistors are definitely manufactured differently. Among other things a different construction can be necessary to get a stability appropriate to the tolerance.
                    I would not be surprised if 5% and 10% resistors came off the same production line.
                    20% resistors might come off a different production line.
                    I suspect that if they're mixing carbon slurry for 1K resistors, and aiming for at least 20%, if they hit 1K on the nose, some of the 20% resistors are going to be a lot closer to 1K than the color bands admit to!

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                      #25
                      Originally posted by PaulMmn View Post
                      I suspect that if they're mixing carbon slurry for 1K resistors, and aiming for at least 20%, if they hit 1K on the nose, some of the 20% resistors are going to be a lot closer to 1K than the color bands admit to!
                      The important thing is that they're not outside the marked tolerance.

                      I was wondering if they make a batch with a target resistance, then actually measure each one, and simply mark the ones that are within 1% as 1%, the ones between 1% and 5% as 5%, those between 5% and 10% as 10%, etc.

                      That would virtually guarantee that, for example, a 10% resistor would never fall within 5% of the target value.
                      Master Electrician
                      Electrical Contractor
                      Richmond, VA

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                        #26
                        Originally posted by LarryFine View Post
                        The important thing is that they're not outside the marked tolerance.

                        I was wondering if they make a batch with a target resistance, then actually measure each one, and simply mark the ones that are within 1% as 1%, the ones between 1% and 5% as 5%, those between 5% and 10% as 10%, etc.

                        That would virtually guarantee that, for example, a 10% resistor would never fall within 5% of the target value.
                        Nowadays with automated testing, they could mark each one individually. I suspect that in days of yore they'd check a representative sample, then mark the whole batch.

                        I think I was looking for pairs of matched resistors for a project, and buying 1% was expensive. IIRC, I heard that if you get a strip of resistors from Parts-R-Us that all of the resistors in a row will pretty much match ohm for ohm (unless you get the place where one batch replaces another).

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                          #27
                          190521-0743 EDT

                          I have never been involved in resistor manufacture. So in part my comments are guesses.

                          In the carbon composition days a resistor was a mixture of carbon and filler molded into a block.

                          In the 1920s this was a somewhat round bar with a wire wrapped around the bar near each end, then painted. The resistance would be whatever you got falling within some distribution curve. These would be sorted into tolerance bands. Pricing would be based on the probability of building within a band, and demand for a given tolerance. After some experience in what the distribution curve was the price would be set. Price would need to be somewhat of a constant. This means that the resulting distribution curve for 5% units is different than 10% units. Its also means that if demand for 5% units is not as high as expected that some 5% items will be marked as 10%. Probably the poorer 5% would go into the 10% mix. So distribution curves might not be very consistent.

                          By 1940 carbon comp resistors had the wires molded into the carbon block, and an outer coating molded around that assembly.

                          Wire wound resistors were available with tighter tolerances. Here number of turns could be adjusted to adjust resistance.

                          Then came film resistors. These are a ceramic core with a film surface of a resistive material, carbon or metal. A spiral grove is cut around the resistor to determine resistance. Resistance can be moderately accurately adjusted by the length of the spiral. This can be adjusted during manufacture, and so one is less dependent upon the variabilities of the resistive mix. Sorting still may be done. 1% metal film resistors are close to the price of 5% carbon comp.

                          .

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                            #28
                            EIA Resistor Color Code

                            An old, old mnemonic for said color code is "Roy G. Biv.

                            More here:

                            https://www.google.com/search?q=eia+Resistor+Color+Code

                            https://en.wikipedia.org/wiki/Electronic_color_code

                            Best regards . . .

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                              #29
                              Originally posted by Skokian View Post
                              An old, old mnemonic for said color code is "Roy G. Biv......... .
                              That's for the colors of a rainbow.

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                                #30
                                Originally posted by 480sparky View Post
                                That's for the colors of a rainbow.
                                Master Electrician
                                Electrical Contractor
                                Richmond, VA

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