20 replies to this topic

[Jon R]

Can we all put some care into using correct electrical units?

Edited by Jon R, 29 March 2022 - 09:45 PM.

[Wandering Sagebrush]

Jon, what have you noticed, what are you recommending?

[PaulT]

The most common units issue I see here is writing A when aH is meant. I just cringe &  move on. I've likely done the same at times, but it is a point well taken. 

 

It was mistake in units that caused a Mars Climate Orbiter to crash and was the cause of a lens correction repair on the Hubble telescope.

 

Other units errors here: https://spacemath.gs...kly/6Page53.pdf

 

Paul

Edited by PaulT, 30 March 2022 - 12:19 AM.

[ckent323]

Paul, T

I am smiling - you pointed out an abbreviation error (which is an error in itself since it is Ah not aH) not a units error.

An ampere hour (abbreviated Ah, or sometimes amp hour) is the amount of energy charge in a battery that will allow one ampere of current to flow for one hour. An ampere is a unit of measure of the rate of electron flow or current in an electrical conductor.

https://en.wikipedia...iki/Ampere_hour

 

BTW;  While I did not work on the Mars Orbiter I did work on an instrument on the Spirit rover as well as working on over a dozen other spaceborne instruments.  The Mars orbiter error was indeed a unit conversion error but not an abbreviation error.

"spacecraft engineers failed to convert from English to metric measurements when exchanging vital data before the craft was launched"

 

https://en.wikipedia...Climate_Orbiter


;-)

 

Regards,

 

Craig
 

 

 

 

 

 

;-)

[ntsqd]

Those new to the whole electrical/electronics of their campers may not know the proper units. Need to cut them some slack.

 

FWIW, when I see "aH" I'm struggling to recall what unit size modifier starts with an "a", and why are we talking about Henrys anyway?

I prefer "A-Hr" or "A-hr"

 

[PaulT]

Toldja I make mistakes. 

 

Paul

[Jon R]

I’m not talking about capitalization or abbreviations, I’m talking about errors in the units being used for the physical parameter being described. A common one that makes me cringe is “amps per hour” and “amps per day.”

Also, I’m not complaining about people new to this stuff making errors. I’m asking the long timers to be precise specifically for the benefit of newer people trying to learn.

[ntsqd]

I guess that I don't see a problem. Perfectly reasonable to say "the fridge consumes X.X amps per hour". It does imply that the fridge's power consumption is intermittent and the power that it consumes is being averaged over a period longer than just when it is running.

 

It would be incorrect to say that a battery has "XXX amps per hour" capacity, and I agree that it is an error that would be very misleading to someone just learning about this stuff.

 

Being over-bearing about correctness (or anything else) in a forum usually just shuts people down. Grievous errors, sure, minor infractions, no.

[Jon R]

Do you say “mph per hour” when talking about average speed over an hour?

I don’t think it’s being overbearing to suggest we not use unit terms that are clearly physically incorrect. I have not commented on individual posts so as to avoid discouraging anyone or getting into an argument. I am not suggesting anyone not post. I’m simply suggesting those of us who weigh in to help answer questions think about what we are posting and put some additional effort into using correct units for the benefit of those who are trying to learn.

I think that I’ve made the same mistake here as I have made at work several times supervising engineers. Sometimes I’ve attempted to avoid a confrontation with individuals who are causing a problem by making a general statement about expectations to the whole group. Our larger organization makes the same mistake often. The conscientious ones immediately start asking themselves what they did wrong when they really are not the problem, and the problem people remain happily oblivious that your comments were directed at them.

Edited by Jon R, 30 March 2022 - 02:30 PM.

[Vic Harder]

Do you say “mph per hour” when talking about average speed over an hour?

I don’t think it’s being overbearing to suggest we not use unit terms that are clearly physically incorrect. I have not commented on individual posts so as to avoid discouraging anyone or getting into an argument. I am not suggesting anyone not post. I’m simply suggesting those of us who weigh in to help answer questions think about what we are posting and put some additional effort into using correct units for the benefit of those who are trying to learn.

I think that I’ve made the same mistake here as I have made at work several times supervising engineers. Sometimes I’ve attempted to avoid a confrontation with individuals who are causing a problem by making a general statement about expectations to the whole group. Our larger organization makes the same mistake often. The conscientious ones immediately start asking themselves what they did wrong when they really are not the problem, and the problem people remain happily oblivious that your comments were directed at them.

Hey Jon… are you talking to me? I can’t recall making any such errors, but hey, my blind spots are invisible to me. Please let me know.

Also, the corporate culture you mention being part of is quite common. Being direct can be a kinder (not nicer) approach. Have you read Fred Kofman’s book “Conscious Business”? Brilliant, IMNSHO.