Mohit Mahajan (Lists) wrote:
> Hello,
> 
> We manufacture a lot of different kinds of instruments (but each in 
> small quantities). Our serial numbering scheme so far is pretty basic: 
> ABCD-EFGH. AB tells us the week and CD the last two digits of the year. 
> EFGH starts at 0000 every year in January, and increases count with each 
> instrument manufactured. It gives no indication which model or what was 
> manufactured. This info would be given by a spreadsheet where the 
> description of the instrument is entered next to the serial number. So 
> we'd have to look up the serial number in this sheet to know what 
> instrument we're talking about.
> 
> I'd like suggestions for a serial number scheme that could indicate the 
> instrument model/type, date of manufacture (for warranty purposes). And 
> it shouldn't be too long, about 8-10 characters.
> 
> It would be great to know what schemes members here or their companies 
> use to number their products.

I've been toying with the idea of using:

MMMMMRR-YYWW-NNNNNN

i.e.:
    MMMMM   5-digit model number
    RR      2-letter hardware revision code (AA to ZZ)
    YY      last two digits of manufacturing year
    WW      week of manufacture
    NNNNNN  6-digit incremental serial number (# of unit built in that week)

But that's a little long (17 characters), so let's try and bring it down to 10 
characters...

Well, you could use an alphanumeric model number. So to represent around half 
of the different possible model numbers of the first scheme, you'd need four 
alphanumeric digits. Let's reduce this to Base32 and use 0-9, A-Z and skip the 
letters I, O, Z and S (can be confused for 1, 0, 2 and 5 respectively). Now 
it's unlikely you're going to have 50,000 different devices, so let's narrow 
it down a little. Two digits would provide 1024 combinations, which should be 
enough to start with. You can always reserve a range for future expansion.

So that gives us our two-digit model ID. Date of manufacture should ideally be 
human-readable; I'd use YY-WW format (year, week of year). Or you could 
sacrifice a little accuracy and go for YY-MM (year, month). In any case you 
can always search your database for an accurate date of manufacture; the one 
in the serial number should really be for quick-reference only. In either 
case, that's 4 digits, plus the 2 previous, giving six total so far.

The last four can be the serial number, decimal or Base32, which means you can 
uniquely identify up to 10,000 (decimal) or 1,048,576 (Base32) individual 
units in a given month or week.

So that's ten digits in the following format:
   MMYYWWNNNN

   MM    Model number
   YY    Year of manufacture (last 2 digits)
   WW    Week of manufacture
   NNNN  Index of unit manufactured in a given week

If you wanted, you could add an extra digit for a hardware revision. Then you 
can change hardware and say something along the lines of "all devices with 
serial numbers starting 1RA, 1RB or 1RC require Firmware 1.0; 1RD onwards 
requires Firmware 2.0". Obviously you'd make any flash upgraders check the 
hardware serial number in EEPROM to make sure it's suitable _before_ 
reflashing the firmware...

If you can squeeze it onto the label, a barcode might also be a good idea. 
Though entering 10 digits isn't difficult, it saves a little effort and risk 
of incorrect entry. Speaking of which, I'd be sorely tempted to add a check 
digit to that serial number scheme... Just so you can check in software to 
make sure it's been entered correctly, and beep furiously at the operator if 
that isn't the case :)

-- 
Phil.
piclist@philpem.me.uk
http://www.philpem.me.uk/
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