electronic readout liquid metal thermomemter idea/invention (self adj rheostat) - Page 1
Forum section: electronics / general

author: coppercone2
author_rank: Super Contributor
timestamp: August 19, 2022, 08:08:02 pm
content: I had a idea, so a typical liquid metal thermometer works by the principle of expansion.What if you put a semi conductive object inside of a thermometer, like a very thin cylinder of graphite, and connect one electrode to the base and one electrode to the graphite. As the mercury expands, it will short out the graphite and change the resistance.Does this type of component exist? I thought maybe it would exist some where in the late 1800's or early 1900's. Hard to manufacture. Or maybe if the inside of the thermometer was carbonized so the walls are conductive. Or maybe by using conductive glass.So it would be like a temperature controlled rheostat.

author: mendip_discovery
author_rank: Super Contributor
timestamp: August 20, 2022, 07:36:03 am
content: I have seen a alcohol thermometer that has high low indicators that are reset with a small magnet. All you would have to do monitor the rise and fall of these. No need for mercury which is not considered a good thing to have about at home or work.There are also dial faced sealed thermometers that have a relay ability to turn stuff on and off again. They require no power other than what is needed for the relay.

author: coppercone2
author_rank: Super Contributor
timestamp: August 20, 2022, 05:26:41 pm
content: I feel though a proper mercury thermometer could be modified to display some very accurate readings though, particularly if conductive glass element is used, if its compatible.Yes I am just curious if this is an old invention, I don't plan on making it.. if I did, I would use gallium or woods metal, which I have, and maybe with teflon or something (not sure what works). But I am not really interested in how this would be made, just if it was ever made.It makes me think of like van helsing or something lol, all those secret weapon confederate laboratories must have had this and it has been lost in time to union artillery?Would a reamed and lapped hole in a teflon cylinder work with galium? You could make it using pencil lead, you can make OK contacts for carbon (like the ones from batteries) by melting it in a mold of molten solder ( like a copper pipe end cap), sticking in the carbon and letting it solidify.

author: analityk
author_rank: Regular Contributor
timestamp: August 20, 2022, 08:19:23 pm
content: Connect piezoelectric elements to the glass cylinder where medium can expand and measure mechanical self resonance frequency or length travel that waves should make from piezo to medium and bac. You may measure waves standing ratio too.

author: sahko123
author_rank: Frequent Contributor
timestamp: August 20, 2022, 08:40:27 pm
content: You can even have a pressure sensor attached to mercury well or other chemical with more or less linear thermal expansion. However unnecessary this is.They used to however had thermal switches which accomplished a similar thing for temperature control in homes

author: coppercone2
author_rank: Super Contributor
timestamp: August 21, 2022, 12:29:42 am
content: Quote from: analityk on August 20, 2022, 08:19:23 pmOh yes a mercury level gauge would also probably be an excellent option, but some how the 1850's style technology of this interests me. Seems like something you can put together in a few hours if you have a teflon block. I really think someone might have done this and that it was lost to history. I figure it would use a galvenometer and run off a high voltage pile

author: mendip_discovery
author_rank: Super Contributor
timestamp: August 21, 2022, 08:42:13 am
content: If you plan on using Teflon then you can only go as far back as 1938.Btw I was talking about these,https://www.dwyer-inst.co.uk/Product/Temperature/Thermometers/Dial/SeriesRRT3I suspect these kinds of devices have been around for ages.

author: coppercone2
author_rank: Super Contributor
timestamp: August 21, 2022, 06:48:48 pm
content: well I am not in the civil war so I can use more modern materials.I wonder if the north or south would be more likely to make this technology. they always make the south out to have some kind of nazi-esque R&D effort, or maybe its just all those comic books (I think they tried to make rockets, according to mythbusters)https://forum.nasaspaceflight.com/index.php?topic=19894.0

author: cellularmitosis
author_rank: Unknown
timestamp: August 22, 2022, 06:32:18 pm
content: Shining light through it might be another interesting approach. Linearizing the response of an array of LDRs might be challenging

author: coppercone2
author_rank: Super Contributor
timestamp: August 22, 2022, 08:21:10 pm
content: a photo resistor with a light shown through a slit with a thermometer ? Yes that is another interesting circuit that sounds like it would work, also another self adjusting rheostat (but with substantially less current handling ability (neglecting the fact that the self heating of a mercury self adjusting rheostat run at high current would heat itself and cause error)The technology required is more complicated because you need a light bulb, the conduction method does not require high stability vacuum tube electronics. I don't think you would get the same precision as using the direct conduction method without a stabilized light source.

author: geggi1
author_rank: Frequent Contributor
timestamp: August 22, 2022, 10:01:21 pm
content: If using a mercury thermometer you can use capacative measurement.Have a probe connected at the reservoar in the bottom this probe can be a coil. Feed the coil with a fixed frequency some testing have to be done. The you connect a pickup along the mercury column. The signal level on the pickup will follow the temperature.

author: 1audio
author_rank: Frequent Contributor
timestamp: August 24, 2022, 04:58:06 am
content: I think this is a closely related device:https://collection.sciencemuseumgroup.org.uk/objects/co3054/mercury-in-glass-adjustable-contact-thermometer-by-thermometers

author: 1audio
author_rank: Frequent Contributor
timestamp: August 24, 2022, 05:05:29 am
content: And this patent seems to match what the OP described:https://patents.google.com/patent/CN2144341Y/en

author: coppercone2
author_rank: Super Contributor
timestamp: September 01, 2022, 02:50:30 am
content: Damn what the hell, 1992. I thought it would be from 1892! But yes exactly what I had in mind, I guess resistance wire is fine. Makes sense, IIRC mercury has appeal/interest and is a historical material for traditional Chinese cultures?