Connect with us

Parts Numbering Scheme

Discussion in 'Electronic Design' started by Roger Lascelles, Jun 7, 2005.

Scroll to continue with content
  1. We are a small company, and we would like to implement a better components
    numbering scheme.

    The parts numbers need to go into our accounting system and on parts lists,
    build lists and some schematics, so we don't want them to be too long.

    Letters and digits are OK, but each must start with a letter. Sort order is
    a consideration, because computers sort strings from left to right, often in
    ascii or similar order. That means each character position has significance
    and it might be best if every part had the same number of characters.

    The storeroom must be organised by part number, so that we can work
    systematically to find the correct shelf, container, then envelope or reel
    inside the container. We need to store similar parts together in the
    storeroom, to make the most of the containers. For example, SMD resistor
    reels are stored together, with a number of different resistor values in
    each container. This means SMD resistor part numbers must form a sequence,
    though not necesarily in order of ohms value.

    A part number should at least tell roughly what kind of part it is - SMD
    resistor, leaded electrolytic, etc, so that means the leftmost characters
    should carry that info so the sorted list is by part type.

    Now, does anyone have a system like that ? Or a different or better system

    Roger Lascelles
  2. Dan Hollands

    Dan Hollands Guest

    Since part numbers are entered by hand over and over again into computer
    systems the key is to use the smallest number of digits possible.

    Part numbers should not attempt to define the part.

    I would suggest a 6 digit system xxyyyy where xx is a gross identifier and
    yyyy is just a sequential number within the xx class.

    Do not use dashes or periods in the part number - that is just one more
    keystroke to enter.

    Do not use Alpha characters - you should be able to enter the part number
    with a key pad for speed.


    Dan Hollands
    1120 S Creek Dr
    Webster NY 14580
  3. Boris Mohar

    Boris Mohar Guest

    There is also copy and paste.


    Boris Mohar

    Got Knock? - see:
    Viatrack Printed Circuit Designs (among other things)

    void _-void-_ in the obvious place
  4. Roger...

    35 years ago, when I started RST Engineering, I was restricted to numbers
    below the integer-based storage of the computer we had at the time, so all
    of our part numbers were 64,000 and below. (+32K to -32K and a subtraction
    algorithm that made them all positive).

    Fifteen years ago we switched to a 9-digit part number and what a pain in
    the labonza to change them all over. However, change them we did and it has
    made life one hell of a lot easier.

    Send me a decent email address to jim at rstengineering point com and I'll
    port you back our internal company document on how the system works.

    Basically, it is a number like 1-2345-6789 where the first digit is a broad
    class (mechanical component, electrical component, in house made component,
    subassembly, etc.), the 23 is a very generic class of parts (and for
    electrical parts, 90% of our stock, based on the first two digits of the
    Electronic Engineers Master [EEM] numbering system), the 4 breaks it down to
    through-hole, smd, etc., 5 breaks it down further (quarter watt, half watt),
    the 6 is the tolerance, the 789 is the value in milliohms with the 7 being
    the multiplier and the 89 being the significant digits.

    The more I think about it, the better I like the first character being a
    letter. That gives me 52 options PLUS the 20 some oddball categories of
    @#%& non-alpha characters.

    Drop me a line. You might also look at a program called Parts & Vendors
    that handles this sort of numbering system quite well.

  5. Yes, that is just how I reasoned when setting up our database. Our
    part numbers start from 1. Maybe I took the principle too far...

    We are up to 1654 now. (BFS17W, a NPN RF transistor. Nice part.)
  6. Mark

    Mark Guest

    Boy, this is one of my pet peeves, the typical part number is
    incomprehensible to a human. Untold hours are wasted looking up part

    I suggest you invent a part number that is descriptive such as

    RES 1000 Ohms 1/8 W 5% 0402 SMD Rev 3

    This ASCII string can BE THE PART NUMBER.
    You can add as many fields as needed to completely describe the part

    Computers don't need random digits to be the part number. They work
    fine with ASCII strings.

    I would be glad to work with you to invent this new part number system.
    We can both become millionaires.

  7. Agree, if it is smart enough to know that

    RES 1.0 KOhms 1/8 W 5% 0402 SMD Rev 3

    can be the same part.
  8. Not to mention 1K0

    Best regards,
    Spehro Pefhany
  9. Joerg

    Joerg Guest

    Hello John,
    And dirt cheap. My impression is that many young engineers don't even
    know about these anymore.

    Regards, Joerg
  10. Yes, that too :) Good job too since I just ordered a reel of 3k. A
    lifetime supply at the rate we will use them!

    Well, it would be if not for RoHS (as discussed in another thread...)
  11. Dan Hollands

    Dan Hollands Guest

    Engineers often like descriptive part numbers because they rarely have to
    enter the part number. They may enter it into a bill of material but thats
    about it.

    Manufacturing and Purchasing are the groups that spend lots of time entering
    part numbers over and over again. When parts are ordered, received, removed
    from stock etc. Long alph numeric part numbers not only take more time to
    enter but the increase the probability of error.

    It is important to get it right from the start. Changing the system later is
    a major pain.

    The ideal system uses sequential numeric part numbers linked to a
    standardized description field. Then reports can be generated for the
    engineers that have similar parts grouped together. This makes it easy to
    know what parts are already stocked as new products are designed reducing
    the rate at which new parts are brought into the system.

    A standardized description field is designed for each type of component such

    RES 5W 104 SM

    It takes considerable work to standardize the descriptions and enforce their
    use but is well worth the trouble.



    Dan Hollands
    1120 S Creek Dr
    Webster NY 14580
  12. Joel Kolstad

    Joel Kolstad Guest


    You have some good insights, but let me add a couple of things:

    1) One of the biggest frustrations I've had as a working engineer at a small
    handful of companies is that many systems used for entering BOMs are some
    horribly old archaic pieces of software that have rotten search facilities. A
    smart design would let something like "res 2.2k" find any of "resistor
    002.2kilohms" "r 2.2 kohms" or "res 2.2kilohms", yet most have limited exact
    search functionality much less the "fuzzier" search needed to find "r 2.2
    The problem with this is that you can never foresee all the fields you need.
    In a reasonably sophisticated manufacturing operator, something like 99% of
    your resistors will be something like "10k, 5%, 0805," but there's always that
    design where things like temperature coefficients, the build style (inductive,
    non-inductive, etc.) matters. This gets even worse with capacitors.

    I've had more than one product fail during production due to someone deciding
    that they could go and substitute some "run of the mill" part for something
    that had tight specs. To avoid that I sometimes will go to the effort to find
    a part where the "standard" description (e.g., 2.2uF 0805 25V) specifically
    _isn't_ "in the system!"
    ....and even with the exceptions to the rules, it's still a lot easier than not
    making the attempt.

    ---Joel Kolstad
  13. I agree completely. I once thought "engineer readable" part numbers were
    necessary and designed my own system where the part number encoded all
    sorts of useful (to me) info. This ended up being a nightmare because
    the person assigning the numbers had to keep coming to me to check that
    new numbers were correct. Then there were the situations that I hadn't
    thought of, or were ambiguous. In the end, it generated more work for
    many people and didn't really improve anything.

    If I had to do it again, I would choose a system based on purchasing,
    inventory, and manufacturing requirements. I'd probably use 2-3 digits
    to define broad categories (mechanical, electrical, etc.), 1-2 digits
    for special handling requirements (ESD sensitivity, fragility, humidity,
    temperature, etc.) and 5-7 digits for a sequential stock number. I'd
    also include a check digit or two to help detect entry errors
    (particularly transpositions [430 instead of 403] and phone/calculator
    substitutions [143 instead of 749]).

    I would use numbers with fields separated by dashes. This is both human
    (numeric keypad) and "barcode" friendly. Dashes reduce human error by
    breaking numbers into subunits that fit into our short-term memory.
    Numeric+dashes allows use of the less error prone (and shorter)
    numeric-only barcodes. Check digits are also required to detect read
    errors for most barcodes, so including it everywhere keeps the number

    Initial entry of the standardized descriptions should be
    software-verified, or menu-driven. If the description doesn't match an
    established template, it should require someone with management-level
    authority to enter an override code. Systems that allow entry without
    checks are a recipe for enormous headaches. I would also include a
    free-form notes field to help cover those special cases nobody thought of.
  14. Joerg

    Joerg Guest

    Hello Dan,
    That is exactly the point. You need to be able to enter the PN with just
    a numeric keypad. Also, in most companies it needs to be suitable for
    bar coding.
    In a controlled environment you can't change them later. This can easily
    require an ECO re-release of everything that had been designed to date.

    Regards, Joerg
  15. Mark

    Mark Guest

    Manufacturing and Purchasing are the groups that spend lots of time entering

    Please explain why:


    is less error prone compared to :

    RES 1000 Ohms 1/8 W 5% 0402 SMD Rev 3

    There's the old story about an army guy that ordered a small audio
    transformer to repair a radio and he slipped up on one digit in the
    part number.

    The transformer finally arrived.. on a flat bed trailer truck. and was
    big enough to power a small city.

    As far as unforseen variations, you can alway append a small sequence
    number at the end as I did using Rev 3 as an example.

  16. Tim Wescott

    Tim Wescott Guest

    I would suggest that you don't even try to organize the storeroom by
    part number. If you do then you will have to dedicate enough space for
    each part to accept the maximum amount you may ever have on hand -- and
    when you add one miserable little part you'll have to rearrage the whole

    Any 1/2-way decent stock tracking program will allow you to track the
    locations of any parts, and to print pick tags with the location for the
    stock boys. Use one, put the parts where it makes sense, ask the
    computer when you're looking for parts and tell the computer when you
    move them.
  17. JeffM

    JeffM Guest

    The ideal system uses sequential numeric part numbers
    Bang-on. BTDTGTTS

    Back in the dark ages, our department had 2 copies of the Parts Book:
    1 sorted by P#; 1 sorted by description.

    Trying to find parts by Description,
    it was obvious that the Co. had started with a system
    but (over time) the gatekeeper function had been abandoned.

    (The Co. had also started with a P#-is-indicative system,
    but abandonded that--perhaps at the same time.)
  18. Suggest you go find out about relational database design. Once you
    understand how that works, most of what you want is easy to implement.
    Look for keywords like 'Natural key' 'Surrogate key' '1 to many


    Adrian Jansen adrianjansen at internode dot on dot net
    Design Engineer J & K Micro Systems
    Microcomputer solutions for industrial control
    Note reply address is invalid, convert address above to machine form.
  19. Pooh Bear

    Pooh Bear Guest

    One of the best I've ever seen, used at a pro-audio manufacturer used a typical
    prefix and and sub-descriptor suffix follwed by the value.

    E.g. RA100K0 was a 2% 1/4W metal film resistor with value = 100k
    RA033R0 was 33R in the same type. Note the use of 4 numerals in both cases to
    make listings consistent.

    RB, RC etc were different families of resistor type / tolerance / rating etc.

    Simialar method used for other parts.

    I like the text string idea too. But you need to keep to the format - and that
    may be rather less easy to remember.

  20. Joel Kolstad

    Joel Kolstad Guest

    So what's a 10% 100k resistor? RB100K ???

    I tend to waffle about it, but usually I figure that arbitrary numbers are
    best -- it doesn't seem there are that many cases where "100k" is the _only_
    piece of information you'd like to know about the part, in which case you have
    to look up the rest anyway.
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day