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From: Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net>
Newsgroups: sci.electronics.design
Subject: Re: like butta
Date: Sun, 26 Jan 2025 23:54:45 -0000 (UTC)
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bitrex <user@example.net> wrote:
> On 1/23/2025 8:41 AM, Phil Hobbs wrote:
>> bitrex <user@example.net> wrote:
>>> On 1/22/2025 10:43 PM, Phil Hobbs wrote:
>>>> Simon and I are working on a TDR based soil moisture sensor for
>>>> agriculture.  Like many such things, it uses two parallel tines made of
>>>> 18/8 stainless, that form a balanced transmission line.
>>>> 
>>>> Ours has a slide hammer for pounding it into really difficult soil, e.g.
>>>> hardpan. The measured shock from that is around 1.6E5 m/s**2, i.e. 16000
>>>> gees, and over its lifetime it might see around 1E6 blows. Challenging.
>>>> 
>>>> Doing <200 ps TDR on a balanced line obviously needs a very wideband balun.
>>>> We’re using a plain ferrite design based on Ferroxcube 61 sleeves on 1.25mm
>>>> coax. The resulting 50-Ω differential mode goes into a machined tapered
>>>> structure that maintains 50 ohms while spreading out the mode to match the
>>>> 25-mm tine spacing.
>>>> 
>>>> For survivability, the whole thing is being potted in very hard epoxy with
>>>> a dielectric constant of 3.5ish. This means that it’s hard to iterate—we
>>>> get one try per apparatus.
>>>> 
>>>> Sooooo, I tried making a soft material with that epsilon, which turns out
>>>> to be nontrivial. My initial thought was to use alumina lapping powder
>>>> (9.3) for filler and vaseline (2.0) for the matrix, but it turned into
>>>> clumps by the time it got to 3.0.
>>>> 
>>>> Casting about for alternatives, I remembered the butter in the lab fridge,
>>>> so I measured that: 3.8, better than good enough.
>>>> 
>>>> We were able to verify the design without doing anything irrevocable, and
>>>> there was some left over for the bagels.
>>>> 
>>>> Fun.
>>>> 
>>>> Cheers
>>>> 
>>>> Phil Hobbs
>>> 
>>>> 
>>> 
>>> Cold you please test ninja turtle ooze and report back. It's some kind
>>> of guar gum/vinyl acetate and borate gelatin:
>>> 
>>> <https://en.wikipedia.org/wiki/Flubber_(material)>
>>> 
>>> <https://www.amazon.com/Teenage-Mutant-Ninja-Turtles-83700CO/dp/B0C6RFTJF2/>
>>> 
>> 
>> Nah, Western religious art, particularly Italian Renaissance stuff, leaves
>> me cold.  Cute little cupids representing the glorious cherubim, Madonnas
>> modeled after artists’ paramours, corrupt prelates and donors painted into
>> biblical scenes, blech.
>> 
>> Cheers
>> 
>> Phil Hobbs
>> 
>> 
>> 
> 
> Right well I don't know if pizza's dielectric properties have been 
> studied thoroughly but there's been a lot of work done on Jell-O, it 
> seems pretty customizable. There's always room for Jell-O
> 
> <https://pubs.acs.org/doi/pdf/10.1021/j150393a011>
> 

It’s been used for making edible lasers. 

Cheers 

Phil Hobbs 

-- 
Dr Philip C D Hobbs  Principal Consultant  
ElectroOptical Innovations LLC / Hobbs ElectroOptics  Optics,
Electro-optics, Photonics, Analog Electronics