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So at lunch I was browsing Indiegogo projects and I saw this one here It's a wireless meat thermometer, I've seen it in some permutation or another a few times on sites like this. Apparently no one can handle wires coming out of their oven or BBQ.

I'm skeptical that this could be built cheaply, do ASIC and RF components even exists at 200C temperature ranges? I'd never thought about it so I did a little searching and saw the main market is oil drilling and probably military. The one little MCU I found from TI is $359 on digikey :)

This project claims their thermometer's communicate via bluetooth! Based on my experience I find it hard to believe such a chip exists, but maybe I just don't know any better. So anyway just trying to expand my knowledge if something exists or fuel my skeptacism of this project

Oh I also read this SE article which more or less says what I expect, but maybe things have changed.

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    \$\begingroup\$ these guys want money, not necessarily will meet their goal. You can relatively easy find BT modules operating at up to 125C. 200 is a bit out of range. \$\endgroup\$ – Eugene Sh. May 25 '16 at 17:07
  • \$\begingroup\$ Are they thinking of a solder-free build? Just wirebonding and epoxy perhaps? \$\endgroup\$ – scld May 25 '16 at 17:13
  • \$\begingroup\$ First off they list the max as around 215F (100C) not 200C. 200C your meat is charcoal. I'm gonna go out on a limb and assume the charger stand acts as a base station, and the thermocouples themselves use some simplistic modulation circuit made from discrete hi-temp parts. \$\endgroup\$ – Keegan Jay May 25 '16 at 17:18
  • \$\begingroup\$ @JayKeegan What you say is possible, Wacom tablets for use a passive pen with a resonator. But there the active circuit is in the tablet and the pen moves on top of or very near to that tablet allowing it to induce some energy into the pen. I do not see that happening for this oven thermometer, it will need some source of energy. I refuse to believe that the MEATER is possible until I have seen it in action or have been shown how they overcome some basic issues like electronics not working at 200 degrees C. \$\endgroup\$ – Bimpelrekkie May 25 '16 at 17:25
  • \$\begingroup\$ @JayKeegan This device would be pretty useless with max of 100C.. At least for the intended purpose. \$\endgroup\$ – Eugene Sh. May 25 '16 at 17:27
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They do (At least for some ASIC components) -- some of them leverage Silicon-On-Insulator technology to help achieve those high temperature ratings. X-Rel for example manufactures many "common" analog / etc components that can hit 230C+ temperatures.

They don't make anything RF at the moment, but I'd be curious to see if Peregrine's SOI process is similarly tolerant of extremely high temperatures.

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I think an animation from seller is self explanatory.

enter image description here

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  • \$\begingroup\$ Where is the transmitter here? \$\endgroup\$ – Eugene Sh. May 25 '16 at 18:41
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The directions for the product say to insert the probe into the meat and then place it in the oven. Once the probe reaches the desired temperature the wireless probe sends a notification to the users' smart phone.

Most meat only needs to be cooked to around 160F (71°C) to be safe. The probe will not get any hotter than the meat it is tuck into. So it is possible to construct it using industrial temp parts rated in the 100C to 125C range. Those types of parts are a little more expensive than 0 to 70C parts, but not unreasonably so.

If the user decides to ignore the notification or doesn't notice it; then it is possible that if the meats' internal temperature passed 100C or 125C (depending on the selected parts) the probe could be destroyed.

For example Atmel (now Microchip) makes a chip with an ARM processor and Bluetooth transceiver that operates from -40C to 125C and sells for about $14.36 at 1pc or $9.50 at 1000pcs on Digikey.

ATSAMR21B18-MZ210PA
http://www.atmel.com/images/atmel-42486-atsamr21b18-mz210pa_datasheet.pdf

So the product is viable if the user pays attention.

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The electronics can be in the bottom and cooled by the phase change material (moisture in the meat) so that ordinary components can be used, as @Jay says. 100°C or 125°C is (relatively) easy with ordinary parts, especially if they don't have to last all that long at high temperature. Most ordinary parts, even commercial parts, will work to something approaching the absolute maximum junction temperature, for a while, if the specs are relaxed (reduce clock speed, keep supply voltage moderate etc). The temperature in a car parked under the sun in Phoenix in summer can probably approach 150°C.

There are components designed for down-hole instrumentation that will operate at 200°C+ with degraded specs and extremely high prices. Honeywell is one supplier of such parts.

In this case, (meat thermometer) 160°F (71°C) is enough for turkey. 63°C for a medium steak, so the 'tip of the spear' will stay relatively cool even in a hot oven. Ruth's Chris (a chain of steakhouses) claims their cooking temperature is 1800°F (982°C) but, of course, the center of the meat never gets hotter than 60-70°C (and much less if the customer wants it very rare). Of course if the consumer leaves it in the oven long enough to char the meat to a crisp they might have to buy another electronic meat thermometer.

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