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November 30

Displacement receiver v. transducer v. sensor

I'm working on the Displacement receiver page, which formerly had no citations, and the going is difficult because few things actually talk about displacement "receivers" rather than sensors/transducers/etc.. Does anyone know if these three terms refer to the same thing? The initial article talked about a carbon microphone as a displacement receiver because it responds to displacement internally, although what it measures is sound waves, whereas this book says displacement transducers measure the distance between a sensor and a target, and this one says they measure movement and the "occurence of a reference position", whatever that means. It doesn't seem like carbon microphones fit those definitions. But I've also seen e.g. this conference paper use "displacement receiver" to refer to a contact sensor measuring its change in distance from a concrete block to measure stress waves, which is an application actually measuring distance. The article defines it as "a device that responds to or is sensitive to directed distance", which also matches the concrete definition.

Does anyone know if a carbon microphone is really a displacement receiver? And is a displacement transducer the same as a displacement sensor? Mrfoogles (talk) 19:56, 30 November 2024 (UTC)[reply]

The intended useful function of a Microphone is to sense incoming sound and deliver a proportional electric signal. As Sound is a varying pressure wave, some varying displacement occurs inside the microphone. However, a microphone is not normally intended or calibrated to measure its internal displacements. They are microscopic movements in the case* of carbon granules under pressure in a carbon microphone. I think it is as unreal (overparticularity) to call a Microphone, whether carbon or any other type, a displacement receiver as it is to call my Eardrum a Barometer. In general a Transducer converts energy from one form to another and receiving input is the first part and not the whole of its action. A Sensor must provide actual useful information about a specific physical phenomenon. * pun on "case" Philvoids (talk) 12:41, 4 December 2024 (UTC)[reply]

Smelly plasterboard

This BBC News article about a smelly landfill site quotes a chemist as saying "One of the materials that is particularly bad for producing odours and awful emissions is plasterboard". I thought that plasterboard was a fairly inert substance. Why would it cause bad odours in landfill? (I assume that this is not faulty plasterboard suffering from the in-use 'emission of sulfurous gases' mentioned in the WP article.) -- Verbarson ^talk_edits 21:07, 30 November 2024 (UTC)[reply]

When mixed with biodegradable wastes like manure and sewage, gypsum can produce hydrogen sulphide gas, which is odorous and toxic, and a threat to public health.

Plasterboard Disposal: What You Need to Know

Perhaps somebody who understands the chemistry could add something to our article? Alansplodge (talk) 22:35, 30 November 2024 (UTC)[reply]

Well, gypsum is CaSO4·2H2O, which has a significant amount of sulfur and hydrogen in it, and hydrogen sulphide is just HS -- I imagine it's not too hard for a chemical reaction to release hydrogen sulphide gas and therefore as they occur they do. Probably there's a paper somewhere that goes over the various reactions that happen. Mrfoogles (talk) 01:07, 1 December 2024 (UTC)[reply]

Hydrogen sulfide (however you like to spell it:) is H₂S. According to our article about that chemical, it arises from gypsum by the action of sulfate-reducing microorganisms that are active "moist, warm, anaerobic conditions of buried waste that contains a high source of carbon". 11:48, 1 December 2024 (UTC) DMacks (talk)

1990s Cathode-ray TV questions.

In the late '90s / early 2000s I remember as a kid looking closeup to the TV screen. For The Simpsons, their yellow skin was red green red green lights next to each other to make yellow. You can't do this with the modern TVs now anymore, but what did cathode-ray TVs use for pink? Would it be dim red by itself, or all 3 colors? How do they make brown? And if Cathode rays can do red green red green, can they do for example, red red green, red red green? Thanks. 2603:8001:5103:AF08:2477:8D7F:1D4B:D0 (talk) 22:41, 30 November 2024 (UTC).[reply]

Current screens also describe colors mostly in RGB (red,green,blue) format, although I don't know the details of how they display it (see LCD for one method) -- this webpage lists some color codes for various shades of pink. It looks like they use full red, plus moderate levels of green and blue. Sort of like red + white. Mrfoogles (talk) 01:03, 1 December 2024 (UTC)[reply]

OLED displays use a variety of methods; see OLED § Color patterning technologies. --Lambiam 03:08, 1 December 2024 (UTC)[reply]

Brown is basically a darker shade of orange. Whether this is perceived as brown depends strongly on the context. There is no such thing as a brown light; only surfaces of objects can appear brown. --Lambiam 03:18, 1 December 2024 (UTC)[reply]

In photochemistry/photophysics, we can use dyes to make chemicals fluoresce non-spectral colors. Whether or not there is a brown dye is another question. But I believe pink dyes are known. 2603:8001:5103:AF08:2477:8D7F:1D4B:D0 (talk) 05:45, 1 December 2024 (UTC).[reply]

In straightforward terms, most human eyes have three color receptors — red, green and blue. The eye can be tricked into seeing any color of light by the right proportions of those three pure colors. The devil is in the details. Doug butler (talk) 06:41, 1 December 2024 (UTC)[reply]

It works out mathematically, but one of those details with a devil is that for some colour mixes you may need a negative amount of one of the primary colours – which is physically impossible. That's why some screens use a fourth colour in the mix. PiusImpavidus (talk) 10:35, 1 December 2024 (UTC)[reply]

Please see Gamut before declaring devilry. Philvoids (talk) 14:37, 1 December 2024 (UTC)[reply]

The colours are still red, green and blue, mixed in varying proportions. The exact hue may vary a bit and some screens add a fourth colour. The dots are pretty small though (maybe smaller than before; resolution has increased, but so have screen sizes) and you may no longer be able to watch them from as close as when you were a kid. Try a magnifying glass. PiusImpavidus (talk) 10:23, 1 December 2024 (UTC)[reply]

You're maybe thinking of printing, where the fourth color is black. Way off topic. The really cool thing about color tubes is how the manufacturer deposits the bunches of three phosphors on the inside of the glass screen. The (iron) shadow mask, with its millions of holes, is spaced a few mm back. Spray guns for each color, located where the electron guns will be located in the final manufacturing stage, blast their phosphors so a trio of dots get through each hole in the mask. Electrons from each gun that get through the mask will hit its respective phosphor. Costly, wasteful and inefficient but it worked. Doug butler (talk) 17:07, 1 December 2024 (UTC)[reply]

I remember a TV manufacturer telling they added yellow to the standard blue-green-red to be able to make more intense yellows. It makes sense, as the alternative would be driving the blue component to negative.

Professional printers, like those printing food packaging, often use around 6 colours, chosen specifically for the task. PiusImpavidus (talk) 09:32, 2 December 2024 (UTC)[reply]

You might be interested in Additive color and the RGB color model. -- Avocado (talk) 18:58, 4 December 2024 (UTC)[reply]