I'm studying electronics in college (I live in Europe), and they are teaching us we should form our reference designations of elements when designing a circuit as according to EN 81346.

This seems absurd to me, because it might be OK for a meat grinder and a generator to have the same designations (G) in some sort of a big automation system, but in a small electronics circuit to name both a diode and a resistor with R, just because they do something to current.. i can't accept that. After looking it up on wikipedia, it seems to me that the classical designations R for resistor, D for a diode, etc. are from the American (ANSI) standard.

I know this sort of thing is entirely voluntary, but I just want to know: Does that standard (EN 81346) really apply to every type of electrical circuit? Are there any other European norms or ISO standards relating to reference designation?

  • \$\begingroup\$ I assume that you mean "...to have the same designation prefix"? You're aware that a system containing a meat grinder and a generator will have two components G1 and G2, while a circuit containing many resistors will have many R1, R2, R3, etc? \$\endgroup\$ Nov 29 '11 at 23:09
  • \$\begingroup\$ Yes, of course. Designation prefix is what I meant. \$\endgroup\$
    – MI6
    Nov 29 '11 at 23:14
  • \$\begingroup\$ OK; just wanted to be sure. In that case, why is it so objectionable to name multiple related components with the same designator? \$\endgroup\$ Nov 29 '11 at 23:18
  • \$\begingroup\$ Well, as I understand it the goal of EN81346 is to create some sort of universal designation system, that extends this type of designation from typical electronic components to even non-electric parts. Also, it names the components according to their purpose, rather to their type. For example, a integrated circuit, containing a voltage regulator, say 7805, will be designated, for example, R1. Also a diode and a resistor will be names R2 and R3. This is because the definition is "devices which limit or regulate the motion of energy stream, or material stream". \$\endgroup\$
    – MI6
    Nov 29 '11 at 23:24
  • \$\begingroup\$ As I see on wikipedia, the American standard ANSI Y32.16-1975 defines the classical way of designation components - by their type. By that system the same example will be U1 for the 7805, D1 for the diode and R1 for the resistor. I just feel like this system is a lot more suitable when developing devices that are entirely electronic (have no moving parts, etc.). So I am asking is there a standard that applies in the European Union, which defines the same or similar system to that of ANSI? \$\endgroup\$
    – MI6
    Nov 29 '11 at 23:28

Naming all your resistors R... and your diodes R... is silly, yes.

However, you are forgetting the "table 2" that I have heard tell about. (I can't see the exact content of it to get the "real" designators they suggest because I'm not willing to pay for it.)

This allows you to have a second character... so your resistors could be "RR..." and your diodes could be "RD..." etc.

The meat grinder could be "GM1" and the generator "GV1" for example.

  • \$\begingroup\$ I didn't know about that, it certainly seems more meaningful this way. But still, my question was is there a standard that applies in the EU and defines designating component by what they are, instead of what they do? \$\endgroup\$
    – MI6
    Nov 29 '11 at 23:31
  • \$\begingroup\$ Table 2 does both at once - it has the what they do, followed by the what they are. \$\endgroup\$
    – Majenko
    Nov 29 '11 at 23:32
  • \$\begingroup\$ OK, but can you tell me that all/most practicing engineers actually use this system? That companies (at least all-European companies) use them in their designs? Because I have no professional experience, but I have never encountered a single circuit like that online \$\endgroup\$
    – MI6
    Nov 29 '11 at 23:45
  • \$\begingroup\$ Personally I think it's all rubbish. I use the ANSI system for all my circuits, and I have never met anyone who does otherwise. \$\endgroup\$
    – Majenko
    Nov 30 '11 at 0:17
  • \$\begingroup\$ I tend to have lots of subcircuits that are copied around to a few boards (different expansion boards, etc) I was numbering components in numerical regions, like R200, C200, and U200 for an FPGA and it's supporting components. I am now experimenting with just using a second letter for this. RF1, CF1, UF1, etc. I personally like this... as they're the same designators on say four different board designs and this makes it much easier to hand assemble prototypes (with verification they're really the same first, of course) and debug. I've felt a bit guilty the whole time. :) Is this a bad idea? \$\endgroup\$
    – darron
    Nov 30 '11 at 3:36

Reference designations for electrical and electronics parts and equipment, the Unit Numbering Method, has been around since 1949 when the Institute of Radio Engineers (IRE), predecessor of the IEEE, first came out with it. IEEE 200-1975 has been replaced by ASME Y14.44-2008. Apparently the IEEE figured they had bigger fish to fry and sold the standard to ASME. The US Department of Defense uses it, as does Agilent and some other companies, and, I believe, all NATO countries forces would use it.

A basic reference designator has 1, 2, or 3 class designation letters (if 3 letters the lst letter is X) followed by a (serial) number. See IEEE 315-1975, Clause 22.4 for the "official" list. A 7805 voltage regulator would use class letters VR not U (see IEEE 315-1975, Clause 22.2.4 for an explanation). The A2A1 of A2A1R1 is the reference designator prefix and is explained in ASME Y14.44-2008.

Which standards you choose to follow is up to you but may be dictated by superiors, who may or may not understand.


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