variating temperature issues - slow cooker

My guess is that you probably need to let the water bath pre-heat for a little longer and let the steak come up to room temperature a little more before placing in the water bath. That should help limit the variations more. <br /> <br />I often use a sous vide magic and while there is more variation in it than some of the more expensive options it's normally within a degree or two, not over a 5 degree range.

I'm thinking that you might need circulation in your slow cooker. The Sous Vide Magic works best controlling a pot with the heat source at the bottom like a rice cooker. Rice cookers too are better because of their shape which allows good natural convection to equalise the heat in various parts of the pot. <br /> <br />While you didn't describe your slow cooker they mostly have the heating elements around the sides of a removable inner pot, and they are often square or oblong in shape. Both of these attributes makes getting a constant temperature everywhere in the tank much more difficult than with a rice cooker. <br /> <br />A lot of users have reported good results by using an aquarium air pump as a source of circulation. Get the smallest/cheapest one you can find (assuming it's not too loud) - you don't need much air to help the convection along. <br /> <br />The other suggestion is to attempt to Auto Tune your SVM with your set up. From the factory they are set with default values which work best with rice cookers and we know that slow cookers behave differently. <br /> <br />Hope this is useful, <br /> <br />Cheers, <br /> <br />Peter.

PS, once you've worked out any temperature control and calibration issues, you'll want to cook your beef at 131F. Use F! Not C! Why? Your PID controller will perform with greater precision that way!

I've used both thermostats and PID controllers with a 7-qt. oval crock pot. The symptoms you describe sound like your PID controller parameters aren't matched well with the crock pot you are using--probably the crockery thermal mass isn't coupling well to the thermal mass of the water leading to overshoots in temperature. I believe your best results will require that you add an aquarium pump and air stone to circulate the water. You might also be able to use a tiny water pump inside the water bath, but if you try something like that be aware that (1) it must be low voltage around all that water to prevent shock danger and (2) it must be constructed to endure the high temperatures of the water bath, so a standard aquarium water pump will die pretty fast in the heat. I use the airstone. The circulation cuts down on problems that the controller would otherwise have dealing with temperature overshooting. A perfectly attuned set of PID parameters can only reduce overshoot by heating the water more slowly as it approaches target temperature, which is undesirable because bacteria is given the opportunity to multiply during a slow approach.

Thanks, I will give that a go.