I've seen some circuit diagrams on-line that appear to use the units prefix symbol as the decimal point. So a 6.8kΩ resistor is shown as 6k8 and a 1.2nF capacitor is shown as 1n2. Is this an accepted practice, and am I interpreting the values correctly?
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\$\begingroup\$ Both of them are representing the same values and yes, accepted. \$\endgroup\$– OJazzMay 17, 2022 at 14:36
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\$\begingroup\$ Related/duplicate: electronics.stackexchange.com/q/107698/2028, electronics.stackexchange.com/q/28053/2028, electronics.stackexchange.com/q/246920/2028 \$\endgroup\$– JYeltonMay 17, 2022 at 16:08
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\$\begingroup\$ I've written a little python library that generates and parses this type of string. \$\endgroup\$– Neil_UKMay 17, 2022 at 18:19
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2\$\begingroup\$ Note that this is even accepted/common practice enough to be supported by many tool like circuit designers or simulators as input format. \$\endgroup\$– PlasmaHHMay 18, 2022 at 10:06
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\$\begingroup\$ Also, some components also have markings in this format. I think I've first seen it on '70-'80 era soviet resistors. It's an intuitive notation in my opinion. \$\endgroup\$– Uncle DinoMay 19, 2022 at 12:19
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2 Answers
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Yes, the practice is certainly accepted although there may not be a formal standard or requirement. You are interpreting the values correctly. Note that when no prefix is needed we use the quantity symbol instead, so \$1.1\Omega\$ is written as 1R1.
answered May 17, 2022 at 14:36
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2\$\begingroup\$ Sometimes R is used even when it's not a resistor, though. I've seen it used for inductors too. \$\endgroup\$– HearthMay 17, 2022 at 14:50
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4\$\begingroup\$ @Hearth - You've actually see this for ferrite beads, I would think. They are typically referred to by their impedance (say, 100R) over a certain frequency range. Actual inductors will be marked in Henrys. \$\endgroup\$– SiHaMay 18, 2022 at 6:08
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\$\begingroup\$ is it always the quantity symbol? would you write 1H1 or 1L1? hopefully your diagram does not include a current source \$\endgroup\$ May 18, 2022 at 9:19
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2\$\begingroup\$ Using R instead of Ω comes from the fact that Ω may not be available in the typeset or on the keyboard or in the character encoding. These conventions predate unicode. \$\endgroup\$– RodneyMay 18, 2022 at 10:06
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3\$\begingroup\$ @ElliotAlderson I have never seen a 100nH inductor labelled as 100nL on a schematic, it's either 100nH or 100n. So it's always the unit, or nothing. So we would expect H as the decimal point substitute, 1H1 not 1L1. (Resistance is different because it's a special case of avoiding the Ω symbol.) \$\endgroup\$– RodneyMay 18, 2022 at 10:24
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This improves the readability of printed values on components. A decimal point may be overlooked or is just missing on bad printing quality. You can even find this practice on schematics, BOMS and components, that are 50+ years old. If you see 470 printed on a capacitor the value is not 470pF! You must read it in the code of the color rings on resistors: 4, 7 and no zero digits behind. It's 47pF then, 471 would be 470pF and 475 is 4.7uF. The same on inductors: 101 is 100uH, R27 is 270nH. Using R on an inductor is absurd but very common.
