SI Notation for Direct Current and Voltage Direct Current - Correct Usage?

[nathanlee52]

Hi,

Looking for the SI Notation practices for Direct Current and Voltage Direct Current. We commonly use DC and VDC, but I wonder if that's correct per SI.

I've looked through several guides and pdf's of SI Notation, and haven't yet been able to find the answer. Any help you can provide would be appreciated.

Thanks!

 

[Zryn]

It sounds a bit weird when you say 'Direct Current' and 'Voltage Direct Current' even though DC does stand for Direct Current. I suppose its the whole technicality and ATM Machine argument.

DC Current SI unit is Ampere http://en.wikipedia.org/wiki/Electric_current" which is the same for AC Current.

DC Voltage SI unit is Volts http://en.wikipedia.org/wiki/Voltage" which is the same for AC Voltage.

 

[nathanlee52]

Thank you Zryn for your input and for the effort to link the wiki pages.

 

[CBTman]

The SI system of unit uses the following notation:

Volts: V or volts (lower case) with a space after a quantity (e.g., 230 V or 230 volts)

Amperes: A or amps (lower case) with a space after a quantity (e.g., 22 A or 22 amps)

The IEEE recommends the following notation:

Volts in direct current: Vdc

Volts in alternating current Vac

Abbreviation of direct current in text: ac (lower case)

Abbreviation of alternating current in text: dc (lower case)

BTW, the terms "direct current" and "alternating current" do not refer to the intensity in amperes, but to the fact that the current does not change direction (dc) or does change direction (ac). Hence, it is fine to say "volts direct current" or "volts alternating current".

Alternatively (no pun intended), we could come up with new terms that do not use the word "current", such as "same polarity" and "alternating polarity". However, I think that most people will stick with "ac" and "dc".

 

[alphysicist]

I can confirm that the correct SI notation for Direct Current is I (capital letter "i") and for Voltage Direct Current is U (capital letter "u"). The use of DC and VDC is commonly used in everyday language and is an accepted abbreviation, but for scientific and technical purposes, it is important to use the proper SI notation. This ensures consistency and accuracy in measurements and calculations. I recommend referring to recognized sources, such as the International System of Units (SI) or the National Institute of Standards and Technology (NIST), for further guidance on SI notation.