Watts, Amps, Volts, what is "U"? - Page 1
Forum section: electronics / testgear

author: Circlotron
author_rank: Super Contributor
timestamp: September 02, 2016, 05:19:29 am
content: On my Rigol DS2072 there is a setting to change the vertical units. See pic. What is "U"? Arbitrary units?

author: Fungus
author_rank: Super Contributor
timestamp: September 02, 2016, 08:24:15 am
content: "Unspecified" - you're doing something that doesn't have a name.

author: mairo
author_rank: Unknown
timestamp: September 02, 2016, 11:58:39 am
content: I believe U and V is the same thing - potential difference. In some countries in Europe U is potential diference - example: U = I*R, units are still in 'V'

author: Neganur
author_rank: Unknown
timestamp: September 02, 2016, 12:04:13 pm
content: Quote from: mairo on September 02, 2016, 11:58:39 amNot in this case. It's units, the scope doesn't list I, P it lists W, A, V so clearly units. U is not a unit in Europe either.

author: DG5SAY
author_rank: Contributor
timestamp: September 02, 2016, 12:11:53 pm
content: Quote from: Circlotron on September 02, 2016, 05:19:29 amPerhaps "User defined" and another menue item is shown when "U" is selected?

author: MosherIV
author_rank: Super Contributor
timestamp: September 02, 2016, 12:20:44 pm
content: HiI was going to be flippantand say 'read the manual' but then I just checked the manual and it really does not sayTotal Fail

author: newbrain
author_rank: Super Contributor
timestamp: September 02, 2016, 07:48:36 pm
content: What U decide, of course.Now I feel silly. But someone had to do it

author: technogeeky
author_rank: Frequent Contributor
timestamp: September 03, 2016, 01:39:36 am
content: It's U for Units. As in, Arbitrary Units.

author: tautech
author_rank: Super Contributor
timestamp: September 03, 2016, 01:50:45 am
content: Quote from: technogeeky on September 03, 2016, 01:39:36 amOK, so how does that work with 1, 2, 5 attenuation steps on the vertical axis and why is it needed?

author: gamalot
author_rank: Super Contributor
timestamp: September 03, 2016, 02:09:05 am
content: Don't look at me, I am Chinese, but there is nothing different in Chinese version of user manual!

author: raptor1956
author_rank: Frequent Contributor
timestamp: September 03, 2016, 02:54:51 am
content: I noticed when using a Rigol DP832 power supply to charge an 18650 cell that when the cell voltage was relatively low the display indicated CC for constant current and shortly after reaching the voltage setpoint the display then switched to CV for constant voltage. In the few seconds between them it displayed UR which the manual calls "critical mode".Brian

author: technogeeky
author_rank: Frequent Contributor
timestamp: September 03, 2016, 01:28:56 pm
content: Quote from: tautech on September 03, 2016, 01:50:45 amWell, an oscilloscope measures voltage of course, so it's really volts. But just like the Amps setting, if you are measuring something (say, millivolts) which is proportional to something else (say, amps), you can change the unit.Same with U, but for any kind of units. Temperature. Height. Speed. Etc.

author: JFJ
author_rank: Regular Contributor
timestamp: September 03, 2016, 03:36:36 pm
content: Quote from: Circlotron on September 02, 2016, 05:19:29 amIt's just a label that, according to the DS2000 series Programming Guide, stands for "Unknown":

author: dom0
author_rank: Super Contributor
timestamp: September 07, 2016, 08:05:24 pm
content: Quote from: raptor1956 on September 03, 2016, 02:54:51 amLikely stands forunregulated. Maybe a transient oscillation in the CC-CV crossover region, or just a software glitch.

author: MK14
author_rank: Super Contributor
timestamp: September 07, 2016, 08:28:35 pm
content: Quote from: mairo on September 02, 2016, 11:58:39 amI agree.U = Voltage,due to some foreign languages use U instead of V (I believe). Somehow I thought it was German (U), but it seems it was different countries. (I'm probably wrong here, it seems it is more likely that the U is because Physics uses it for Potential Energy (U), Source:http://whatis.techtarget.com/definition/potential-energy-U).QuoteQuoteThe following article explains it in more detail, but I knew about it anyway.https://en.wikipedia.org/wiki/VoltageQuoteBut there are other sources as well, such as:http://www.thefreedictionary.com/potential+differenceQuoteThird/Fourth and hopefully last source needed:http://www.utm.edu/staff/cerkal/potential.htmlQuoteI hope I have included enough sources, but there are more, if wanted.EDIT: But Rigol, may intend the U to mean something else, such as Umbrella, Unijunction Transistor or Unwell. It is possible that Rigol use the U to mean something else, but I would suspect it is just an alternative to 'V'.

author: dom0
author_rank: Super Contributor
timestamp: September 07, 2016, 09:05:41 pm
content: Don't confusesymbolandunit. U is (esp. in Europe and even more esp. in Germany) the symbol ofa(specific: like between two points in a circuit, or the output of a circuit) voltage, but the unit is V(olts) regardless. Similarly I is often used as the symbol foracurrent, while the unit is still A(mperes). IOW symbols (=variable + unit) are variables or names for physical quantities (=number + unit).

author: Circlotron
author_rank: Super Contributor
timestamp: September 07, 2016, 09:49:16 pm
content: So I is expressed in Ampsand U is expressed in Volts.