Thermocouple setup?


 
C

CraigMW

TVWBB Member
I've apparently burned out a couple of my ET73 "high heat" probes used for keeping track of the pit temp. So, I am thinking it is time to go the thermocouple route. So, a few simple questions:

1. Is there info anywhere about how to build the thermocouple sub-board that was included on the HM4.1 board?

2. What are recommended thermocouple probes that would be compatible with the HM4.1 and useful for keeping track of pit temp?

3. How does one go about setting up the software for the Heatermeter to use the thermocouple to measure pit temp?

Sorry if this has been posted elsewhere, but I couldn't find all of this info and think it would be helpful to have a bit of a primer on this for those interested in pursuing the thermocouple route.
 
EDIT: Oops you're asking about the v4.1 thermocouple board, not 4.2. My bad. The performance of the v4.1 board isn't great due to it not having a proper input connector or mount mechanism. I would advise against it, which is why there is no formal documentation.

1. You build it by buying the parts and soldering them to the PCB, same as the through-hole parts. The parts list is "HeaterMeter v4.2 Hardware" on the wiki.

2. Any thermocouple is good. See some recommended vendors in "HeaterMeter Probes" the wiki.

3. Set the probe type to "Thermocouple" and the mV/C = 5 (which it defaults to).

The wiki: http://heatermeter.com/
 
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Thanks for the info, Bryan. When you mean that the "v4.1 board isn't great due to it not having a proper input connector or mount mechanism...," are you referring to the v4.1 thermocouple sub-board, or the v4.1 Heatermeter board itself? I've already built the v4.1 board and it's working great, so I'd like to avoid building the v4.2 board simply for the sake of adding a thermocouple, if at all possible.

Thanks again for all of your excellent work on this!
 
Incidentally, where does the thermocouple daughterboard attach to the main HM board? Does this simply replace the probe 0 connector? Again, sorry for the confusion.
 
I had a hard time getting respectable performance out of the addon board when attached to a 4.1 PCB it was just really noisy and 1 degree F is less than 3mV to the thermocouple which means you'll get a lot of temperature variation. The first couple v4.2 boards were actually variations to try and reduce this noise, and I thought I never would be able to. That's when I did the complete reorganization which is where 4.2 ended up.

The other issue is that you need to attach it to a "real" (for lack of a better term) thermocouple connector in a manner that the amplifier chip is the exact same temperature as the leads of the connector or else the cold junction compensation won't work right and your readings can be substantially off. The solution to that is either use thermocouple wire to connect the jack or somehow manage to solder the addon board directly to your jack. The two big holes in the addon board are the TC+ and TC-. The other three can use any ole wire to get 3.3V/Signal/Gnd. You also need to remove the 10k pullup resistor on the Pit probe.
 
Okay, I think I'll forgo the thermocouple then. I just wish there were pit probes based on thermistors that were a bit more rugged.
 
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