Reddit reviews Leaton Digital Thermocouple Thermometer Dual-channel LCD Backlight Temperature Meter Tester for K/J/T/E/R/S/N Great (Batteries included)

if you want a stand alone device, this has worked great for me

https://www.amazon.com/gp/product/B018QHQSB8/ref=oh_aui_search_asin_title?ie=UTF8&psc=1

https://www.amazon.com/gp/product/B0142RXG84/ref=oh_aui_search_asin_title?ie=UTF8&psc=1

the base unit auto turns off every 8 minutes, but you can easily turn it back on for the 2nd half of the roast. i'm using this until i decide what electronics i want to cobble together for an automated solution.

I use one of these with a type k thermocouple: Leaton Digital Thermocouple Thermometer Dual-channel LCD Backlight Temperature Meter Tester for K/J/T/E/R/S/N Great (Batteries included) https://www.amazon.com/dp/B018QHQSB8/ref=cm_sw_r_cp_apa_i_DcZ2CbDBBJRWV

Hot air station, Preheater, Dual thermometer.

Aww jeez, Rick. That doesn't look good. I think the technical term for that is "cratered".

My guess would honestly be that the chip itself overheated due to the high current. This is a problem for a heatsink and maybe a fan. I hesitate to say this though, because both the trace AND the chip are utterly destroyed. Maybe a bad solder joint on the chip caused it to overheat?

Are you willing to sacrifice another channel of that board? Might be worth hooking up a stepper in such a way that it's permanently stalled and just running it until it pops, while carefully monitoring the board's temperature. You should at the very least be able to tape down a thermocouple with kapton, and they sell cheap dual K-type thermocouples with a digital readout on Amazon. I've personally had this one to over 700C, and while it DEFINITELY didn't like it and the insulation burned up, it still works. The best solution here is definitely a thermal camera, and if you can afford it you'll be able to pinpoint where the heat is coming from - the traces or the chip.

A good experiment would be to get a thermometer or thermal camera, and hook up one channel with a heatsink and one without. Monitor both chip's temperatures and see how hot they get, again with the motor stalled. The A4983 is supposed to be good to 150C before it detonates according to the datasheet, although it definitely won't be performing well at that temperature. If you see it getting close (within 20C or so) of that temperature, it's likely just not dissipating enough heat.

Would be very interested to see the redesign, if you decide to do one. If you haven't yet read Dave Jones' PCB layout tutorial, I suggest you do. Lots of really great information there, particularly about making your circuit boards neat and professional, not just so they work.

Minor edit: just thinking about the traces, remember that the ACTUAL current can be much higher than intended when you're working with motors or other large inductive loads. A "2A" limit can turn into 20A if something causes a large acceleration on the motor (like a robotic arm hitting a stop and stalling). That'll fry your trace if you specced it for 2A. Make the power traces big and fat. Bigger. Unless you're squeezing the other traces thinner (not just closer), you can go very large with your power traces. You're paying a flat rate for the amount of copper on the board, use it all. Don't squeeze out the ground plane (it's just as important) and don't squeeze the other traces too thin, but if there's any feel free to use it.

Any of them should be suitable, the more expensive ones typically just have faster response times. This one should be fine It just won't give instantaneous readings:

https://www.amazon.com/dp/B018QHQSB8

Personally, I like the type-K thermocouples because they are fast and accurate, and you can also switch out the probes (Thermoworks alone has a metric shitton of Type-K probes). I use a 39" wire probe for brewing, and a rigid penetration probe (hehe) for cooking.

For the meter itself (the thing you plug the probes into), Thermoworks has a bunch of them, though they're on the expensive side compared to a backlit two-probe meter from Amazon. I use one similar to this guy.

http://www.amazon.com/Thermocouple-Thermometer-Dual-channel-Backlight-Temperature/dp/B018QHQSB8/ref=sr_1_5?ie=UTF8&qid=1462914613&sr=8-5&keywords=k+type+thermometer


https://kingpincooling.com/products/extreme-type-k-probe


would these do the job?