When I was an engineering student, while investigating a circuit schematic, I was often discouraged by a device whose symbol I was not familiar with. Thinking that it was a different device, I was usually giving up. In some of the cases, I was finding out (much later) that the device was actually just a regular device (e.g. an inductor or a Zener diode, etc.) with another symbol accepted/used by some other engineers.
When I started to teach electronics, I noticed that I should make convincing explanations for my students to relax them about such occasions. For example, I mention multiple symbols used for Zener diodes, along with the meaning/purpose of essential items of each symbol version. Unfortunately, sometimes I cannot convince some of the students about this many versions of symbols used for the same specific device.
This issue can be an important problem when you are publishing or reading papers in different scientific journals.
Now, I remembered another case -although not very similar-, namely the unit of electrical conductance, which is given with the unit "Siemens", as well as with 1/Ohm, represented by Ω-1 or by ℧ and even by "mho" (Leaving away the "inverted omega" symbol which I also regard as unusual, I have always thought that, Georg Ohm would not be happy about the "mho" unit).
Of course, some symbol versions (e.g. some of the ground symbols given in the figure) may represent a slightly or substantially different property/behavior. However, many people occasionally use those different symbols to represent the same specific device. With no doubt, that's another aspect of the "multiple symbols" issue.
For sure there are multiple standards that we cannot alter to fix a unique symbol for a specific device.
On the other hand, this "multiple symbols" issue often creates problems, especially for the students who are in a struggle to learn/understand new devices.
The "handy" versions of the symbols (like the last ground symbols in the figure) preferred by some instructors may complicate the issue further.
A symbol which reminds of the device's main behavior, points out to difference and similarity with another device, provides ease of drawing and ease of spotting the device on a schematic, etc., can be assumed a good symbol (This can explain, for instance, the different versions of Zener diode symbols).
I know that many of you may think that I am exaggerating the problem. Nevertheless, I would like to know what others think about this issue.
Any personal experiences or suggestions which may be helpful especially for teaching will also be appreciated.
Best regards...
Hi Ali Zeki , I know what you mean. But it can get worse:
In Germany, the DIN (Deutsches Institute fuer Normung = German Institute for Standardization) wasn't happy with the usual symbols for logic gates, so they invented their own about 40 years ago. All are rectangles (possible excuse: it was the age of the nine-pin-printers, thus small arcs didn't looked well on paper). The function is determined by symbols inside the rectangles: & means AND (bow to business men?), >=1 means OR (to be empathetic, you have to be acquainted with the historical development of Boole's algebra, otherwise in two-valued logic there can be nothing greater than 1). Luckily, they kept the small circle for NOT. The inputs are meant to be on the opposite side of the output, but the rectangle invites the students to place their inputs on the three sides not occupied by the output.
Depending on the participation and enthusiasm of the students, I decide to use only the DIN symbols or to tell them about the symbols in the rest of the world.
After all, those who are reading articles or even books not directly connected to the lectures make up the more promising part of the students.
Worse than symbols is the use of "V" instead of "U" for a voltage.
If you mark a general voltage like this:
V=2V, it is only true for V=0 😮. The trouble with symbols is the same as the one with SI-units. Nm not lb in, km and not miles...
I recommend to introduce symbols to your students according to a single international standard and stick with it, though an explanations should briefly hint to other symbols.
Thank you for your answer dear Aparna Sathya Murthy ,
You are right that different devices have different symbols. That's natural.
What I am mentioning is the different symbols used for the same device. When following different books, a novice student often sees a different symbol of a device and may think that it's a different device (that s/he does not know).
Some of the ground symbols I used are really used to represent different uses, like real earth, analog ground, digital ground, AC ground, etc., but I have come across with many famous/good books in which the author(s) use the ground symbols as they like.
I am grateful for your final suggestion. However, as long as the student/engineer continues to look up from different sources, it's difficult to make sure that s/he will not be confused. For sure, it's dominantly an issue of time/experience.
Best regards...
Dear Martin Schulz ,
You pointed out to another aspect of the issue
(I am regretful now because of not including such an example in the figure as well. At least, I mentioned the "Siemens" unit and the "mho" unit in the main text)
Honestly speaking, the German standards have (had) an influence on the university I graduated. Therefore, in some course we were using U for voltage but in some other we were using V.
It's a good point you mentioned. V=2V can lead to V=0. :)
(Definitely, there were similar examples, but unfortunately I don't remember now to mention).
You know that many experts and journals prefer to use V for voltage, but using italics or lowercase for the signal (voltage here) and putting a blank between the number and the unit can avoid the misunderstanding: V=2 V .
However, when you write it on the board (handwritten), it is potentially open to misunderstanding.
It could become much worse when you teach a course like Physical Electronics, in which you may need to use volume and velocity of the charges and the voltage drop across the device. :)
You have provided a good common example.
Thank you very much !
Dear Joerg Fricke ,
When I decided to ask this question, I was hesitating because it does not seem a technical or research-related question.
However, now that I am reading the very first answers, I understand that potentially there may be many people who experience similar issues and they also are not happy about some of them.
Your examples are good examples, that I did not have information about.
Apparently, in each country similar problems are experienced, but it may be because of different reasons.
Some countries don't even have well-standardized usage for device/quantity symbols, units, etc. Probably they suffer from such problems more.
The phrase "... the rectangle invites the students to place their inputs on the three sides not occupied by the output." made me smile. :) Similar issues exist for some other symbols. Many students are more than creative. :)
Best regards...
Dear Martin Schulz ,
I have remembered one of the examples now. Maybe you don't regard it similar to your case, but it's worth mentioning here.
It's about the prefixes μ, m and M.
(Like for 5 μA , 20 mV and 3 MΩ)
For sure, these prefixes are difficult to mix up, but sometimes I come across with an exam paper in which the student is not sure about the order of the value and tries to fool me by using a mid-way handwritten-style prefix which can well be interpreted as μ or m or even as M :) .
(e.g. S/he finds the current 5 mA but is not sure and thinks it could also be 5 μA, so decides to act this way. Several times, I saw the same style prefix used for μ, m, M on the same page of an exam paper. I usually call such a student and reveal the issue. I give this example in the classes as well and warn the students. They often find it funny as well :) )
I am attaching a figure to represent such a case.
Best regards...
The DIN standard symbols are ugly and counter-intuitive, and the idea of using text within a rectangle to define the logic function falls apart when you have a low-resolution drawing, or a scrawly bit of handwriting.. I find the MIL standard symbols much more useful, since the shape defines the logic function and, since these are used by all the schematic editors with which I'm familiar, I suspect they're the nearest thing to a universal standard.
Thank you for your comments dear Mark Sitkowski .
You mentioned some issues similar to those mentioned by Joerg Fricke .
Now, I started wondering whether some others could come up with other issues again related with the DIN standard.
I am familiar with only some of the DIN standard symbol. So, I think I will look it up now.
Best regards.
Ali Zeki
In my first answer, I referred to the symbols in the upper row of the attached file. These replaced those in the lower row which were a former DIN attempt to make German symbols "unique" but those older ones had at least some resemblance to the more widespread symbols.
Dear Joerg Fricke ,
Thank you for uploading that figure. It's quite informative.
I was thinking of taking a similar action. You were 1 step ahead. :)
Today I have already reviewed some of the symbols (of the DIN standard).
I have noticed that, I had used some of them in the past in several courses.
(There were some German and some American influence on the university I graduated )
When you are subject to different standards, it can be really problematic.
When you are in a medium which has not accepted a well-defined fixed standard, that's the worse.
Thanks again.
- Badges
- Science topic
- Similar topics
- Computer Communications (Networks)
- Simulators