Author Topic: Watts, Amps, Volts, what is "U"?  (Read 3270 times)

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Offline Circlotron

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Watts, Amps, Volts, what is "U"?
« on: September 02, 2016, 05:19:29 am »
On my Rigol DS2072 there is a setting to change the vertical units. See pic. What is "U"? Arbitrary units?
 
 

Online Fungus

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Re: Watts, Amps, Volts, what is "U"?
« Reply #1 on: September 02, 2016, 08:24:15 am »
"Unspecified" - you're doing something that doesn't have a name.
 

Offline mairo

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Re: Watts, Amps, Volts, what is "U"?
« Reply #2 on: September 02, 2016, 11:58:39 am »
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'
 

Offline Neganur

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Re: Watts, Amps, Volts, what is "U"?
« Reply #3 on: September 02, 2016, 12:04:13 pm »
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'

Not 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.
 

Offline DG5SAY

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Re: Watts, Amps, Volts, what is "U"?
« Reply #4 on: September 02, 2016, 12:11:53 pm »
On my Rigol DS2072 there is a setting to change the vertical units. See pic. What is "U"? Arbitrary units?

Perhaps "User defined" and another menue item is shown when "U" is selected?
 

Offline MosherIV

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Re: Watts, Amps, Volts, what is "U"?
« Reply #5 on: September 02, 2016, 12:20:44 pm »
Hi

I was going to be flippant :P and say 'read the manual' but then I just checked the manual and it really does not say  :palm:

Total Fail  :palm:
 

Online newbrain

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Re: Watts, Amps, Volts, what is "U"?
« Reply #6 on: September 02, 2016, 07:48:36 pm »
What U decide, of course.

 :palm: Now I feel silly. But someone had to do it :palm:
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Offline technogeeky

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Re: Watts, Amps, Volts, what is "U"?
« Reply #7 on: September 03, 2016, 01:39:36 am »
It's U for Units. As in, Arbitrary Units.
 

Offline tautech

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Re: Watts, Amps, Volts, what is "U"?
« Reply #8 on: September 03, 2016, 01:50:45 am »
It's U for Units. As in, Arbitrary Units.
OK, so how does that work with 1, 2, 5 attenuation steps on the vertical axis and why is it needed?  :-//
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Offline gamalot

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Re: Watts, Amps, Volts, what is "U"?
« Reply #9 on: September 03, 2016, 02:09:05 am »
Don't look at me, I am Chinese, but there is nothing different in Chinese version of user manual!   :palm:
 

Offline raptor1956

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Re: Watts, Amps, Volts, what is "U"?
« Reply #10 on: September 03, 2016, 02:54:51 am »
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
 

Offline technogeeky

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Re: Watts, Amps, Volts, what is "U"?
« Reply #11 on: September 03, 2016, 01:28:56 pm »
It's U for Units. As in, Arbitrary Units.
OK, so how does that work with 1, 2, 5 attenuation steps on the vertical axis and why is it needed?  :-//

Well, 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.

 

Online JFJ

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Re: Watts, Amps, Volts, what is "U"?
« Reply #12 on: September 03, 2016, 03:36:36 pm »
What is "U"? Arbitrary units?

It's just a label that, according to the DS2000 series Programming Guide, stands for "Unknown":
« Last Edit: September 03, 2016, 03:43:57 pm by JFJ »
 
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Offline dom0

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Re: Watts, Amps, Volts, what is "U"?
« Reply #13 on: September 07, 2016, 08:05:24 pm »
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". 

Likely stands for unregulated. Maybe a transient oscillation in the CC-CV crossover region, or just a software glitch.
,
 

Online MK14

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Re: Watts, Amps, Volts, what is "U"?
« Reply #14 on: September 07, 2016, 08:28:35 pm »
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'
I 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).

Quote
DEFINITION
potential energy (U)

Quote
The potential energy is stored when an elastic is stretched, and converted to kinetic energy when the elastic is released. Other types of potential energy include chemical, which is related to the formation of chemical bonds and electrical, expressed as voltage

The following article explains it in more detail, but I knew about it anyway.

https://en.wikipedia.org/wiki/Voltage

Quote
Voltage, electric potential difference, electric pressure or electric tension (formally denoted ?V or ?U, but more often simply as V or U

But there are other sources as well, such as:
http://www.thefreedictionary.com/potential+difference

Quote
potential difference
n
(General Physics) the difference in electric potential between two points in an electric field; the work that has to be done in transferring unit positive charge from one point to the other, measured in volts. Symbol: U, ?V or ?? Abbreviation: pd Compare electromotive force

Third/Fourth and hopefully last source needed:
http://www.utm.edu/staff/cerkal/potential.html
Quote
Electric Potential Energy (U) and Electric Potential (V): (Notes from C. Erkal’s lectures PHYS 221)

I 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 :-DD. It is possible that Rigol use the U to mean something else, but I would suspect it is just an alternative to 'V'.
« Last Edit: September 07, 2016, 08:55:26 pm by MK14 »
 

Offline dom0

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Re: Watts, Amps, Volts, what is "U"?
« Reply #15 on: September 07, 2016, 09:05:41 pm »
Don't confuse symbol and unit. U is (esp. in Europe and even more esp. in Germany) the symbol of a (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 for a current, while the unit is still A(mperes). IOW symbols (=variable + unit) are variables or names for physical quantities (=number + unit).
« Last Edit: September 07, 2016, 09:07:30 pm by dom0 »
,
 

Offline Circlotron

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Re: Watts, Amps, Volts, what is "U"?
« Reply #16 on: September 07, 2016, 09:49:16 pm »
So I is expressed in Amps
and U is expressed in Volts.
 


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