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expressing component values containing decimal and showing the quantity unit

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  • expressing component values containing decimal and showing the quantity unit

    I have seen component values in Rober's videos (and elsewhere) like 1R2, 10k5, 0R for resistors. With capacitors, sometimes it says 1uF and at other times it just says 100n. With inductors I saw 4u7 and 3u3. With voltage rails I come across 1V2 and sometims 5V.

    What is the name for this differing notation and trying to avoid writing the dot symbol for decimal? Also, why do we write the unit for the quantity e.g V, F, R sometimes but not at other times?
    Last edited by gyuunyuu1989; 08-28-2023, 10:11 AM.

  • #2
    Good question! If only we all would be (very) consistent... And everything could be written in 3 characters.

    Both the factor (k, m, u, n, p, etc.) and the unit (R, E, V, etc.) are commonly used as the decimal.
    Sometimes it is easy/nice: 4k7, 100n, 22u, 5V, +3V3. A little bit more tricky are low value resistors: is 10R written wrong and should it be R10? That is why I use E for resistors.

    Looking at my own schematic I also have 1uF and 3.3uF. So no, I too am not consistent.
    If such a thing bothers you, you better sets so rules before you start and stick to it.


    • #3
      I am new to this so I am not even aware of what rules must be set to be consistent. I mean, what are all the possible variations of values that I write? I am not sure.


      • #4
        You could have a rule that states that you always want the units -- 100nF, 22uH 5V.
        However, how do you do resistors? 10k, Start / Run / charmap, find the ohm symbol Ω (U+03A9), copy it and paste in the symbol.
        What if you write "ohm" instead and need a 100ohm resistor. Is that 100 [ohm] or 1000 [ohm] as it looks like 3 zeroes.

        So we leave the units, just values and multipliers (k, m, n, p, etc.) -- 100n, 22u, 5... eh Volt.
        Ok so units when we are near 0 -- 100n 22u 5V, and 1R or is that R1?
        Hence the "1E" notation for a 1 [ohm] resistor.

        Thoughts to consider...

        I think that if you look at the schematics of Robert, or other open source project, you would see a mix notation.
        As long as it is clear what the value is, it is no problem.

        I am in the business for over 20 years and still have no fixed set of rules.