Removing Noise from Temperature Probes

I wanted to remove as much electrical noise as possible from the roasting process as it makes the data very difficult to interpret.  I am basing my measurements on 2mm thick temperature probes that can pick up tiny ground loops and any electrical noise.  Due to their thin size, they already react very quickly to temperature changes, so any extra noise needs to be removed.

I found a helpful article, published by MachineDesign,  "Top tips on squelching electrical noise".  I look to incorporate some of those ideas in soon.

A friend told me, one should always fix as much noise as possible from hardware, not software.

I installed ground terminals, using some old speaker terminals, in the wall that connect to both the roaster's 240V outlet as well as a nearby 120V outlet used for my computer. I used #12 wire to match what is used for the roaster's circuit and not violate any obvious electrical code.  Clearly, these outlets already have grounds, but they don't connect to each other until the electrical panel, 50+ feet away.

I then ran a ground wire to the back of the roaster, snagging a connection with the end of my gas line along the way.  


Next, I used a ground bar kit to terminate my ground wire behind the roaster.  I also ran each of my probes through it, but only tightened enough to keep them from slipping.  I don't want to squeeze the wires too hard and short them out.   I also found some thinner wire that I was able to wrap each probe with to give it additional connectivity back to ground.  I used tape to hold these as I want to make sure everything is remove-able for when I need to change things up.

Lastly,  I installed a ground clamp on my roaster.  I would have liked to also install one on the electrical panel, but upon inspection, there wasn't an obvious place to do it.  I did verify with an Ohmmeter that there was no resistance between different points on the roaster.

 

 

For now, I am not using a USB Isolator as I don't want to add a floating ground.  That would defeat the purpose for what I have just solved.

 

BEFORE the new grounding system:

 

After the new system:

 

Roaster Dave

dave@squarefeetcoffee.com

 

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