Two ammeters in parallel

So far, so profound (not!)

A minority... still we can't all know everything.

Using that logic we can argue that as a group we are all confused on all basic matters.

From the man who apparently does not even know what a swamp cooler is, you are not in a good place to accuse others of being armchair experts. Especially with your posting history!

BTW, still waiting for the apology from you for wasting all our time in that thread as a result of your sloppy terminology / cluelessness / fibs (delete as you feel fit).

I guess we all have delusions.

Lol. ICBA

NT

You haven't even got as far as discovering the things work in the UK, and your 'explanation' of why you think they don't is also wrong. All you got to reply with is ad hominem bs.

NT

Oh, so you CBA after all?

I can't.

I would not call any of that ad hominem. In fact I try to counter the message and not the man in the vast majority of cases.

I did cite your posting history since you make many strong assertions, and yet provide little that one can use to gain confidence in those claims. We have little visibility of your profession or skills or qualifications. We know little of your background or the type of work you do. You post little or nothing about any projects you have been involved in be it professionally or personally; not even photos of stuff you have built or fixed or restored.

IMHO, the whole online persona seems to be carefully crafted to give away as little as possible, and so there is also little to inspire confidence and trust.

You are often keen to denigrate the collective skills of the group and yet in many cases seem more inclined to dismiss or criticise rather than actually share your knowledge with actual teaching.

I guess that's one way to acknowledge that you don't know me or what I've done or do now. And yes, I keep my private life mostly out of public places. That's deliberate and I'm fine with that.

But your comments on things when you clearly have no idea what the facts are do not generate respect. I spend /most/ of my replies sharing what I've learnt, it is imho the primary purpose of this place. I learnt a large chunk of what I know from reading people here doing likewise. That does not mean I'm going to hold the hands of people that cba to type a few words into google or spend numerous hours explaining what has been written about enough times elsewhere. Nor am I interested in spending my time on people that are more into being dunces than learning anything. When it comes to non-ac cooling technology alas you fall into the bracket of strongly held opinions without knowledge, which quickly degenerates into duncity.

As for criticising what people say, no group gets everything right and no group has all the expertise it thinks it has. Such is human nature, and this group is not exempt. Nor are you, I or anyone else. Some of us are aware of that & cautious in what we say, some not. I point out errors because otherwise everything that follows is male cow parts, and no-one learns any thing.

And if you want me to say a group that can't work out how ammeters in parallel work is expert in electronics, er, no. Ain't gonna happen.

When I make what you regard as outlandish claims it's because I've done them. I like experiments and have done a lot of them. They solve a lot of problems. Experiments are also how businesses are started. I've experimented in diy with noise reduction methods, fillers, plumbing, heating, cooling, paint, various tools, cement products, lighting, glazing, curtain hardware, fans, glues, cleaning, limited locksmithing, roofing etc. I've restored a car and fixed up houses. My main area is electronics, where I've done a lot. If you think I'm bsing, pick one from noise reduction methods, plumbing, heating, cooling, paint, tools, cement products, lighting, fans, cleaning, roofing, in most diy cases I don't mind discussing it. Not so much the electronics. The experiments cover the full range from trying what 1000s have tried before to trying to develop new tech. The latter I don't get into. Most diy experiments have been very basic but useful.

When I discuss things I've not done I try to make sure I say so with phrases like I'd expect, but I've not done it and so on. I'm not perfect, nor are you. When you come back with stream of stupidity stuff you can't really expect me to agree. Mostly you're sensible but now & then you absolutely are not. When getting into ad hominem if you bear in mind you really don't know what the facts are, maybe then we can keep it sensible. That would be more productive.

NT

All vehicles were originally negative ground. In the IIRC 1930s, some UK car makes changed to positive ground. Said to help with both plug and points life. But not all UK car makers. Rolls and Rover, for example, stayed negative ground. Commercial vehicles, being mainly diesel, stayed with negative ground. Presumably an organisation the size of an electricity board had trucks and vans? Petrol vans being based on a car, usually.

Indeed and there is little need to make ones private life public. However lacking any background information at all can often lead to a train of thought along the lines of "That sounds a bit doubtful - I wonder if this is just an experiment or a bright idea, or has he actually done it in a real situation?". If you at least described the situation it might be clearer.

Well here is the thing. If I post on something, then unless its just for humour or I make it clear that its conjecture or a educated guess, then it will be about something that I have some experience or knowledge about. (That does not mean I never make errors or recall things incorrectly).

With which I would agree.

Was not suggesting you need to necessarily, there are times - say when writing a wiki article[1] on a subject, I find one needs to take a pedagogical approach. That usually means trying to refrain from simply splurging everything you know about something into a pile of unrelated "facts", and missing out all the connective information and the reasoning, but to actually think through the process of how to create something that one can learn from in a step by step fashion.

ISTR the discussion started specifically about swamp coolers rather than non AC cooling. (the latter being a much much broader subject with far more applicability in hot and wet environments)

This is where I wonder if you are reading the same group as me... I look at the first handful of posts to that thread, and 90%+ say up front - yup fine add em together, with only one questioning the logic. Yet to you this a "group that can't work out how ammeters in parallel work"

and out of interest, how many of those have you actually started / owned / operated as commercial businesses?

No, but at times it would be good if you understand that people had different experiences to yours, which left them with different views. That does not make them dunces!

Take the whole swamp cooler thing for example (now understand that I am talking about the "personal cooler" devices that are popular. Basically consisting of a fan in a box, with a membrane of some form and a water tank to moisten said membrane while the fan blows air though it).

I have personal experience of these in a number of situations now. The last couple of times were in large electronics labs where someone had bought one of these things, and swore blind that they were "cooling the place". The problem was it was a large enclosed space, with temperatures in the high 90s, and high humidity (something not uncommon in summer in the southern parts of the UK at least *in my experience*) actual cooling was not even feasable. Even when we pointed out that the bulk of the benefit they were feeling was just as a result of the fan moving air, and showed with a thermometer that the temperature reduction right in front of its output was low (typically less than a couple of degrees C) they were not convinced. However it upset everyone else, because the cooler made the environment even more humid, and hence less comfortable for everyone else.

Now I fully accept that there are cases where these things can work really well; such as in a hot dry climates. In a fully enclosed space, where they are not pumping heat or humidity to somewhere *outside* of the space, the basic laws of physics ought to tell you that they can't do anything useful looking at the bigger picture.

(I also accept that there are things you can do with more elaborate "split system" evaporative coolers that use heat exchangers which can keep the evaporation process and humidity outside, and indirectly cool and de-humidify the internal air - although these are arguable AC systems anyway)

Quite often we don't know what the "facts" are when you are describing something of your creation. For example when trying to get some sense of how it was possible that your "crude swamp cooler" did not add to the internal humidity. It took much circulatory conversation and frayed tempers to finally realise that what you were using bore no resemblance to a swamp cooler at all - crude or otherwise. So who is the dunce there? The ones not understanding how what sounded implausible could work, or the one using completely the wrong language to describe cooling a roof with water, that made it all sound so implausible in the first place?

nothing wrong with asking

That's fine if you have ages to craft a detailed reply explaining everything. A discussion list is often not like that. And some topics are far too large for that to be practical here.

Current can only flow through the meters. There is no other path. It's 101 stuff, as are shunts. Of course not everyone knows about it, and of course in a diy group most don't. The right info is available here but too often contradicted by a greater number that lack 101 level knowledge of electronics. This is often followed by people without basic knowledge asserting they're definitely right when clearly not. It's human nature but it does not give me any cause to recommend this group's 'expertise' on electronics. Beware would be a fairer overall assessment. And yes, there were a lot of confused posts on the basics of meter shunts.

I do. With things like non-ac cooling the results depend very much on the details. That is one of the reasons the pros use refrigerant ac, it's a whole swathe of skill they don't need to learn & extra time they don't need to take assessing each job.

no, the conclusions people draw can quickly get them there though. Like when folk insist an evap cooling system they've never seen must raise RH even after being told repeatedly it doesn't.

'That makes no sense to me' is fair enough. 'I'm seeing problems with that' is fair enough 'You absolutely must be as retarded as I am' is just idiotic.

That's your conclusion based on faulty understanding of the physics.

Wikipedia disagrees with you - not that that's the final word.

NT

Actually I expect the vast majority know that. However I suspect you may be missing the motivation for those who questioned, i.e. not "are they carrying the current between them?" (which as you say, is self evident), but more "is the arrangement going to in some way cause them to misread the value?".

Now most with background in these things will know that the sum should add up to the total current, and they won't be confused by the configuration (parallel arrangement of shunt resistors etc). However the fact that the question was raised at all suggests at least a basic understanding of ohms law and electronics to even be aware that resistances summed in parallel will have a lower value than individually.

As an engineer I would also suggest when when taking readings, its actually good practice to at least mentally ask the question "is there something about the nature of the setup that will get me a skewed reading?" or "Is the meter showing me what I think it is?". It can save confusion - say seeing phantom voltages with very high impedance volt meters etc.

But in this case it was not contradicted by many at all - not even a sizeable minority.

Well that was partly the problem - you telling us that it would not raise the RH. When it should be obvious that evaporation will raise RH. Now we assumed that you were describing a swamp cooler since that is what you claimed to have (Fredxx even posted a link to a handy .svg showing the typical configuration of the things), and so we rightly questioned the absurd claim that RH would not be raised. We explored if you had a HX that could allow the RH to be raised outside rather than inside, and you claimed not. What we did not realise that the source of the confusion is that you were not talking about a swamp cooler at all.

So ok misunderstandings happen - but they are not always the fault of the listeners!

Well you can only comment on the information as its presented.

If you had stated "I keep the place cooler by flooding a flat roof with water" in the first place and not tried to imply that was a "crude swamp cooler", the I expect most of that conversation would not have happened.

Then kindly explain the fault in my understanding of the physics?

Again I think this must be a comprehension problem on your part since on my reading just now it says all the things that we said in that thread.. For example:

"Evaporative cooling uses the fact that water will absorb a relatively large amount of heat in order to evaporate (that is, it has a large enthalpy of vaporization). The temperature of dry air can be dropped significantly through the phase transition of liquid water to water vapor (evaporation). This can cool air using much less energy than refrigeration. In extremely dry climates, evaporative cooling of air has the added benefit of conditioning the air with more moisture for the comfort of building occupants. "

It also says: "In climates not considered arid, *indirect* evaporative cooling can still take advantage of the evaporative cooling process without increasing humidity" [my emphasis; not a crude swamp cooler but an indirect system using a HX etc]

and "Evaporative cooling therefore causes a drop in the temperature of air proportional to the sensible heat drop and an increase in humidity proportional to the latent heat gain"

and "A simple evaporative cooler's water is evaporated into the environment, and not recovered. In an interior space cooling unit, the evaporated water is introduced into the space along with the now-cooled air"

Ah, yes I see what you did there... We were discussing your "crude swamp cooler" which turned out to be nothing of the sort, and you have now morphed that to the more general evaporative cooling which is a much bigger topic involving far more possibilities than just swamp coolers.

All swamp coolers are evaporative coolers, but not all evaporative coolers are swamp coolers.

Its because your terminology was misleading - You said you had a "crude swamp cooler". They always add to the RH of the cooled air. You claimed yours did not (which BTW I accept is true - its just not a swamp cooler)

I don't. It's a diy group.

which if you understand the basics of shunts, we know no misread occurs. But again most here don't know this stuff - why would they? So it seems unrealistic to say one will get good consistent advice from a group that mostly does not know what it's talking about.

that was a statement of fact, not the problem :)

the question is where. Some dunce insisted it must raise RH indoors, even though I'd made it plain that the system did not. It's that level of stupid I don't have a lot of time for.

You missed the point I was making, which is that the limited definition of swamp cooler is not supported by the wiki article.

NT

I did.

NT

It became the problem when you made a silly claim that a basic or crude swamp cooler wouldn't raise the humidity of a room.

The only dunce here was the one that said a crude swamp cooler wouldn't raise the humidity of a room.

You went onto provide details of a complex evaporative cooler that was no longer simple or crude.

It was your inclusion of "crude" that was the issue.

You entirely missed the point that only a complex evaporative cooler wouldn't further humidify the room.

And you said the least insulation the better. Some of like the idea of a well insulated roof so we have warmer rooms in the winter and less conduction of heat through the roof in the summer.

Sorry, but we don't hand out comedy awards. However in honour of (our now presumed) late group member, can I offer you the DENNIS award?

Shall we look at the thread?

NT: "Why use ac when you could use a swamp cooler?"

Newshound + T I M: "UK weather? " etc.

NT: "I use a crude swamp cooling setup here when it hits heatwave. It works and costs near nothing. We did have 2 or 3 days when it was raining real hard & you don't get significant cooling, the rest of the summer it's good. And no, it doesn't make indoors any damper."

T I M: "...Well, if you have a river running though your place already I guess it wouldn't but how can you evaporate a quantity of water into a sealed space and it *not* get more humid?"

NT: "Are you actually trying to be a moron?" [Hmm, sharp comeback]

Fredxx: "Yes it does. The humidity increases, actually making it more difficult for sweat to evaporate. On paper, yes the temperature has dropped. "

another couple of rounds of incredulity from various

NT: "Which part of 'And no, it doesn't make indoors any damper' was beyond you? Lemme give you a hint: the way the system works means it does not add water to the indoor air, and does not make the place damper. Are you able to comprehend that yet?"

(odd we are quite a way into the thread now, and not a single mention of flat roof watering)

Fredxx: "What part of a "crude swamp cooler" passing air over water that enters the room, making the room air moist don't you understand.

Yes there are evaporative coolers that can work effectively and using heat exchangers, but a "crude swamp cooler" doesn't, and by the very nature of reliance of evaporation increases humidity.

Or do you think the water vapour magically disappears?"

NT: "Get back when you're willing to stop being an idiot" [got to admire the almost Churchillian oratory Nige]

Me: "So out of interest how does your swamp cooler manage to separate the cooled air from the humified air? Does it have an air to air heat exchanger and secondary fan (or at least air path)? "

and at last a glimmer of hope 4 DAYS LATER into the thread, NT:

"If one were to install something, what I'd suggest considering is passing (incoming or recirculated) air through a pipe covered..." so a suggestion for a hypothetical system that you don't have,

and TADA: "What I do here (in heatwaves only) is far cruder. The flat roofed extension, despite being fully insulated, is like an oven in a heatwave. Flood the roof with water & that effect stops. It no longer heats some of the rest of the house. It could hardly be simpler, and no, no water vapour is added to indoor air."

Now at this point I will admit I had missed that this nugget was supposed to be the description of your "crude swamp cooler", mea culpa

- I assumed that was just another bit of diversion and question avoidance along with the mud covered pipes, and the differential ventilation bit that followed. Since it does not sound like a description of a swamp cooler, or even an evaporative cooler for that matter, perhaps you can forgive our ignorance and general lack of mind reading capabilities?

One can only conclude that after all the denials that NT and TB are one and the same.

They have the same MO in flogging the same ridiculous argument.

Who is TB?

the wet roof doesn't

it doesn't

water on the roof is as simple as it gets. If that's not simple & crude, whatever is?

It's as crude as it gets.

Whoosh

NT

Eh?

Somehow you managed to miss where I described the system first time round. I can see there is confusion & misunderstanding. That is unfortunately a normal part of life. Insisting a system that does not add water vapour does is... a normal part of brain malfunction perhaps.

NT