Resistor colour code

Discussion in 'General Electronics Chat' started by coldbuffet, Jul 9, 2014.

  1. coldbuffet

    Thread Starter New Member

    Jul 9, 2014
    Hi, I've tried a search on these forums and I couldn't find an answer to my question.

    I was wondering if resistor colour codes can begin with a black band?
    For example, does a 7000 ohm resistor ever get shown as the following:
    Black - Violet - Orange - Gold = 7000 ohm +-5%
    Black - Black - Violet - Orange - Gold = 7000 ohm +-5%
    Black - Violet - Black - Red - Gold = 7000 ohm +-5%

    as opposed to starting with non-black bands:
    Violet - Black - Red - Gold = 7000 ohm +-5%
    Violet - Black - Black - Brown = 7000 ohm +-5%

    Also why would a manufacturer choose to represent 7000 ohm with a 4 band resistor as opposed to a 5 band resistor or vice versa?

    Thank you!
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    No i have never seen a resistor starting with zero, 6 bands are more accurate usually with temperature coefficient,

    so 7K 5% would be violet,black,black,brown, green.
  3. wayneh


    Sep 9, 2010
    Ditto. I don't think the first band is ever anything but the 1st significant figure of the resistance value. It would cause too much confusion otherwise.
  4. wmodavis

    Well-Known Member

    Oct 23, 2010
    In usual number/value representation a leading zero is dropped because it does not convey any useful information just as in resistor color coding - no useful information represented by leading zero.
  5. alfacliff

    Well-Known Member

    Dec 13, 2013
    have you checked it with an ohmeter? and reverse? the only things I have seen with a black first band are diodes.
  6. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    A sixth band can be black, designating temperature coefficient:
  7. ian field

    Distinguished Member

    Oct 27, 2012
    There used to be plenty around with a single black band - 0 Ohm resistors.

    Apparently they were easier for through hole pick and place machines to handle than pre-formed wire links.

    SMD resistors are of course marked with numerical values - I vaguely recall having seen at one time or another; SMD resistors marked "0".

    It seems to me that starting a colour code for a resistor other than "0" with a black band would be pretty pointless (values less than 1 Ohm have gold or silver multiplier) - The blue bands on some resistors under certain lighting can look black.

    There's a small LED flashlight and jewellers loupe ready to hand on my bench for these situations.