PLM Basics: Reference Designator and Find Numbers

Some time ago, one of my readers wrote me a comment with the question about Reference Designators and Find Numbers. With all our interest to talk about modern technological trends, mobile, social software, understanding and clarification of basics is very important too. In the past, I wrote few posts tagged PLM Basics. If you haven’t seen it before, navigate your brower to the following link.

Online Reference Information
You are pretty much out of lack if you are trying to find this information online. Here is short info from Wikipedia.

A reference designator unambiguously identifies a component in an electrical schematic (circuit diagram) or on a printed circuitboard (PCB). The reference designator usually consists of one or two letters followed by a number, e.g. R13, C1002. Thenumber is sometimes followed by a letter, indicating that components are grouped or matched with each other, e.g. R17A, R17B.

Another source of information, which is probably less known – PLMPedia. This is an online project of created byLEDAS. Unfortunately, PLMPedia has no information about what is a reference designator.

Reference Designator (RD)
RD is normally a text field that belongs to Component in Bill of Material, that helps you to specify what this component does and how to find this component. In most cases, used when more than one component with the same Part Number need to appear in BOM. Reference designators can be used in various reports and Bill of Material views. The most of Reference Designator usages is to simplify your access to a specific Component / Part Number. The usage of Reference designators can be different between various systems in the industry. Normally, the information about Reference Designator usage belongs to BOM module.

Find Number (FN)
FN is a number that usualy set by Bill of Material management module when create line item in BOM. For most cases, I’ve seen, Find Number usually set automatically or manually as the incremental number for every row in Bill of Material. Find Number is a simple way to search, sort and organize lines in Bill of Material module.

I found usage of Reference Designator sometimes overlaps with usage of Find Number. I’m looking forward to hearing about your experience and common practices. I didn’t find much online information about terms and practices in product development and engineering. The usage of Reference Designators can be different in electronic industry compared to mechanical engineering.

Best, Oleg

*** photo in this blog post was imported from Flickr user Dano. The original file is located here.


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  • Andrew

    Find Numbers, beyond being sorting and organizing, usually line up with the 2D drawing or assembly document in a balloon call out. Think IKEA furniture instructions.

  • Andrew, thanks for this comment! Yes, FN is like balloons on drawing. It makes sense.. Best, Oleg

  • Cam Bickel

    Find numbers trace back to when the parts list was on the assy drawing. The find number corresponded to the assembly sequence, that is, “find this part and add it to the assembly…”.

    Reference designators are used with electrical assemblies as method to identify each instance of a component on the schematic, assembly documentation and the product. For specifics look at IEC 750 or ANSI Y32.2.

    In modern systems reference designators are most useful for printed circuit assemblies. The reference designator orignates in the schematic capture tool and appears in the netlist, on the silkscreen, and parts list. Balloons are generally not required because the relationship between the parts list and silkscreen (and placement information in the pcb files) is implied.

    In our PLM system we do not use find numbers at all – we leave all at zero. We use the ref des field to contain reference designators for pcb assemblies and to hold numeric designators that correspond to assy dwg balloons for mechanical assemblies and the non-electrical parts on pcba’s.

    Reference designators can be extended to uniquely identify a part within a subassembly of an assembly within a unit within a system for documentation purposes, example 1U1A1R1.


  • Cam, thanks for your great use cases. The major difference between assembly sequence (FN) and electronic labeling (RD) is clear. Similar to your statement about not using FN, I had a chance to see multiple other cases. As I mentioned before, there is an overlap in usage as well as different practices in companies. Best, Oleg
    PS. I’d like to encourage you to have a look on comments to this topic in my main blog – plmtwine is mirrored website, I keep for all people following me during last 2 years.

  • Aravinth Rajendran

    Thanks for considering my question to you and writing a blog.

    Regards, Aravinth

  • Aravinth, you are welcome! We need more such discussions. Don’t miss comments on Best, Oleg