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Crock pot with accurate temperature control


jackal10
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But, if our tolerances are accuracy within 0.25C, stability within 0.5 and no more than 0.25 variability in the bath, it's still possible that one part of the bath could be a full degree warmer than another part of the bath.  1 degree C certainly has a notable effect on many sous vide applications.

What you say is true to an extent. While there are applications (and I have mentioned this in my previous posts) where the precision you mention may be required, there are a ton of sous vide applications where 1 degree (or even 2 degrees) is more than sufficient to get amazing results.

Perhaps you don't mean to give this impression, but your posts give the impression that it is a waste of time to explore sous vide without the precision you mention. I don't think this is the case. Newbies may be getting the wrong impression from your posts since you seem generally discouraging. And while ultra-precise sous vide applications may be most interesting to you, they may not be the applications that other people care most about.

The hardware that we are talking about (if it works as advertised) will do a lot of people a lot of good. There may be some preparations that they can't make, but there is an awful lot that they can make. We don't all need the equipment that would allow us to create every possible sous vide dish.

Btw, I am mostly posting this perspective because I don't want newbies to get the impression that 0.5C is some magic amount of stability that is required for a system to be useful. Because it simply isn't the case.

Best,

Edward

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Edward, I can think of lots of reasons people who don't want to spend money on a circulator might still be interested in exploring sous vide. What I have a hard time figuring out is why someone would want to go the time, trouble and expense of PIDing a crock pot when it seems like there are solutions involving less time, trouble and expense that should be within the tolerance of several degrees C.

Again... if you're going to cook two portions of fish or something like that for 20-30 minutes, a nice large stockpot (useful for many other things!) and a thermometer should suffice. The thermal mass is large enough that the temperature shouldn't decrease very much if you simply turn the burner off after chucking in a few salmon steaks. At worst, you might have to check back once and boost the temperature. As nathanm pointed out, if your tolerances are within only a few degrees, it's unlikely you can do things like salmon mi cuit with any reliability anyway.

If you have any long-term cooking you want to do and you're happy with tolerances within three or four degrees C, then there are ways this can be done without using a PID.

Heck, you can even use ziplock bags if you want to (although this compromise also removes certain advantages available to users of vacuum sealers).

I, personally, would argue that the most striking and unique things that can be done using this technology are dependent on temperature accuracy and stability within at least 0.5C. So, while I agree with the basic premise that some of the aspects of sous vide cooking can be achieved without a precision circulator, I write to point out that there are a lot of very interesting things that will very likely be unavailable any other way (unless you have a precision steam oven, etc.). And the implication I get from a lot of these "sous vide on the cheap" discussions is that people think they'll be able to do all or almost all of what you can do with a lab circulator and a large vessel using a crock pot and a PID. That doesn't seem like it will be the case. You can do some of the same things.

When I became interested in exploring sous vide cooking, and did not have a precision circulator, I simply explored the other options I outlined above. Especially for the short-term cooking of fish and tender meats, it is not particularly burdensome to do it on the stove. When I determined that it was something that interested me enough to explore the full range of possiblilities, I stepped up to the plate and poached a reconditioned Lauda off of an auction site. To me, it doesn't make sense to spend 1/3 the money on a crock pot and PID controller for something that only gets me half of the cool stuff I want to do. On the other hand, I'm not the kind of guy who solders things for fun. If someone can come up with a cheap, accurate and stable PIDed hotplate with some kind of insertable circulating pump (I'm not sure an aquarium bubbler would suffice, but surely there is something out there), I'd be all for it. :smile:

--

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What I have a hard time figuring out is why someone would want to go the time, trouble and expense of PIDing a crock pot when it seems like there are solutions involving less time, trouble and expense that should be within the tolerance of several degrees C.

.......

If you have any long-term cooking you want to do and you're happy with tolerances within three or four degrees C, then there are ways this can be done without using a PID.

......

I, personally, would argue that the most striking and unique things that can be done using this technology are dependent on temperature accuracy and stability within at least 0.5C.  So, while I agree with the basic premise that some of the aspects of sous vide cooking can be achieved without a precision circulator, I write to point out that there are a lot of very interesting things that will very likely be unavailable any other way (unless you have a precision steam oven, etc.).  And the implication I get from a lot of these "sous vide on the cheap" discussions is that people think they'll be able to do all or almost all of what you can do with a lab circulator and a large vessel using a crock pot and a PID.  That doesn't seem like it will be the case.  You can do some of the same things.

......

To me, it doesn't make sense to spend 1/3 the money on a crock pot and PID controller for something that only gets me half of the cool stuff I want to do.

While half of what is cool TO YOU may require 0.5C, it is a HUGE leap to assume that everyone shares your interests and priorities. Please list the things that require 0.5C control as opposed to 1 or 2 degrees of accuracy.

There isn't anything on my top 10 list that would require 0.5C accuracy. Yes, there may be some REALLY COOL things that require the accuracy that you are talking about. But it is a huge leap to think that everyone else has your priorities. I totally disagree that 0.5C accuracy is required for half of what is interesting about sous vide.

There is a huge difference between 1 degree of accuracy that was being discussed and the 3 or 4 degrees that you have thrown into the mix -- as if I was arguing that 3 to 4 degrees of accuracy is sufficient. I never implied any such thing. My whole interest in the PID concept is that it has been a lot of work to maintain 3 to 4 degrees of accuracy by hand AND with some things that I cook, I feel that the results would be better with smaller temperature swings.

I will repeat what I have said before in this thread. There are a number of advantages of a system like we are talking about vs a stockpot and thermometer. It requires constant vigilance to maintain things within a few degrees with a stockpot. Many of us don't want to have to sit by the stove monitoring things constantly. This is especially true if one is trying to do salmon (for instance) at 113. And is not practical for anything long (like short ribs and tough cuts of meat) that needs to be cooked for a long time.

If you disagree fine. But rather than repeat yourself, give us examples of what things one would be missing out on if the system were accurate to a degree (or even two degrees).

Best,

E

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A few things:

1. As I said before, if you are doing a small number of items (a similar number of things as you would be able to do in a non-circulating PIDed crock pot) you should not have to exercise "constant vigilance to maintain things within a few degrees" in a large stock pot. You should be able to get to just above your target temperature, throw in the fish or similarly thin cut of tender meat, adjust with cold water if need be, and the stock pot shouldn't lose too much temperature over the 20 minutes or so it would require for the protein to achieve the correct temperature. This is especially true if you follow nathanm's charts and use a water bath that is actually at a higher temperature than the target temperature of the protein (which technique I belive Juan Rocca endorses anyway). This should be true with any protein that needs to be cooked for, say, less than 30 minutes.

2. Tender things that are sensitive to within 1 degree C:

- Fish (especially mi cuit)

- Beef at the "lower ends of doneness"

- Pork at the "lower ends of doneness"

- "Just done" turkey and chicken white meat

3. Tough things that are sensitive to 1 degree C:

- Similar to #2 above, if what you are going for is a result at the "lower ends of doneness"

4. Things that are not sensitive to 1 degree C:

- Anything cooked above "medium," or if you don't care so much whether your 48 hour short ribs turn out "rare" or "medium rare."

My experience is that when one is looking to explore the line between "still kind of raw" and "just cooked" temperature accuracy is extremely important. In some cases less than 1 degree C can make a discernable difference.

Edited for clarity

Edited by slkinsey (log)

--

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A few things:

1. As I said before, if you are doing a small number of items (a similar number of things as you would be able to do in a non-circulating PIDed crock pot) you should not have to exercise "constant vigilance to maintain things within a few degrees" in a large stock pot.  You should be able to get to just above your target temperature, throw in the fish or similarly thin cut of tender meat, adjust with cold water if need be, and the stock pot shouldn't lose too much temperature over the 20 minutes or so it would require for the protein to achieve the correct temperature. 

Your experience is different than mine. Maintaining 113 degree water for 20 minutes was more challenging for me than for you.

2. Tender things that are sensitive to within 1 degree C:

- Fish (especially mi cuit)

- Beef

- Pork

- "Just done" turkey and chicken white meat

3. Tough things that are sensitive to 1 degree C:

- Everything, if what you are going for is, e.g., "rare short ribs"

4. Things that are not sensitive to 1 degree C:

- Anything cooked above "medium," or if you don't care so much whether your 48 hour short ribs turn out "rare" or "medium rare."

I think I hear the sounds of goal posts moving. First you said that 0.5C was necessary and that 1 degree C was not sufficient. Now, you have moved the target and seem to be conceding that 1 degree C is sufficient. Fish mi cuit may actually require 1 degree C. But the other items you mention are all doable with 1 to 2 degrees C of accuracy (and some of them with even more variability).

Rare steak and just done chicken and turkey are all things that I have done on my setup that only maintains a few degrees of accuracy. While 1 degree or better of accuracy might ,make a discernible difference, for none of the items above is 0.5C of accuracy (your original claim) necessarry for succulent results. It is not as if a rare roast done with 1 degree C (or even 2) of accuracy is going to be a failure. I would say that for most people chicken cooked 'just done' or beef cooked rare with 1 or 2 degrees C of accuracy is going to be an awesome experience.

And, while you may find maintaining things within a few degrees with a stockpot and thermometer to not require vigilance, I don't think most people will have that experience. (In fact, I ended up with a really disappointing turkey breast that needed to cook for a few hours because the temperature ran about 5 degrees too hot for a while because I wasn't being vigilant.) If I had cooked in a system that had one or two degrees of accuracy, I wouldn't have had that problem.

I have cooked a number of the items above in a system with no better than 3 or 4 degrees of accuracy and my wife raves about how great it tastes. With 1 (even 2) degrees of accuracy I am sure it will be even better. So, I am curious to hear if the Auberin device delivers that one or two degree of accuracy.

I suspect that others are in the same boat.

--E

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I think I hear the sounds of goal posts moving. First you said that 0.5C was necessary and that 1 degree C was not sufficient. Now, you have moved the target and seem to be conceding that 1 degree C is sufficient.

Really? Please tell me where I said that 0.5C was necessary. If you read back, I think you will see that I said in mentioning prospective benchmarks for a PIDed crock pot with no circulator: "temperature accuracy within 0.25C and stability within 0.5C." To be even more clear: "accuracy within 0.25C" = really precise thermometer that actually reflects the temperature of the water bath, and "stability within 0.5C" = 1 degree C of variability. My position of 1 degree C was first stated here (before the statement as to stability of 0.5C you have latched on to) and further clarified here. I do not mean to contend that all applications are sensitive to 1 degree C, just that many of the most interesting ones are.

Fish mi cuit may actually require 1 degree C. But the other items you mention are all doable with 1 to 2 degrees C of accuracy  (and some of them with even more variability).

In my experience I have been able to tell the difference in all the things I have listed to within 1 degree C when exploring the lower end of the "doneness scale." Which is to say that, while the difference between 53.5C beef and 54.5C beef can seem quite noticeable, the difference between 75C beef and 76C beef is not so noticeable.

Rare steak and just done chicken and turkey are all things that I have done on my setup that only maintains a few degrees of accuracy. While 1 degree or better of accuracy might ,make a discernible difference, for none of the items above is 0.5C of accuracy (your original claim) necessarry for succulent results. It is not as if a rare roast done with 1 degree C (or even 2) of accuracy is going to be a failure. I would say that for most people chicken cooked 'just done' or beef cooked rare with 1 or 2 degrees C of accuracy is going to be an awesome experience.

Discounting the fact that you are mischaracterizing my previous claims, as I explain above, it is of course possible to make something delicious with nothing more accurate than your finger as a temperature-measuring device. So what? I wasn't saying that you couldn't make something tasty with a less-accurate setup. In fact, one might be able to make salmon mi cuit with nothing more than a saucepan and luck. But that's not to say that it will turn out the same way the next time.

And, while you may find maintaining things within a few degrees with a stockpot and thermometer to not require vigilance, I don't think most people will have that experience. (In fact, I ended up with a really disappointing turkey breast that needed to cook for a few hours because the temperature ran about 5 degrees too hot for a while because I wasn't being vigilant.) If I had cooked in a system that had one or two degrees of accuracy, I wouldn't have had that problem.

I don't know what to tell you there. Back in 2005 Really Nice! seemed to be able to get his setup to maintain pretty good accuracy to within a little over 2 degrees C using a digital thermometer and an electric stove. I have to believe that a larger thermal mass (e.g., a large stockpot instead of a hotel pan) or an insulated container would hold temperature a lot better with more accuracy than that.

I have cooked a number of the items above in a system with no better than 3 or 4 degrees of accuracy and my wife raves about how great it tastes. With 1 (even 2) degrees of accuracy I am sure it will be even better. So, I am curious to hear if the Auberin device delivers that one or two degree of accuracy.

I suppose it all depends on whether 1-2 degrees C of accuracy is worth 100 bucks to you -- especially considering that I think you should be able to achieve around 2.5 degrees C of accuracy using more "conventional" (and more or less free) means. So really it's a question of whether 1-2 degrees C of accuracy is worth it for the "set it and forget it" aspect. To me, there was enough to be gained in having 0.1C accuracy/stability that it was worth 400 bucks to me, but perhaps not enough to be gained in having 2 degrees C of accuracy that it would be worth 100 bucks to me largely for the convenience of set-and-forget. But, to each his or her own. I understand and appreciate that some people may have different priorities. I might think differently if I had only 100 bucks to spend and was more interested in long-term cooking applications than I was in temperature-sensitive applications both short- and long-term cooking.

--

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jackal10,

Have any of these posts answered your question?

"There are, it has been said, two types of people in the world. There are those who say: this glass is half full. And then there are those who say: this glass is half empty. The world belongs, however, to those who can look at the glass and say: What's up with this glass? Excuse me? Excuse me? This is my glass? I don't think so. My glass was full! And it was a bigger glass!" Terry Pratchett

 

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I need the Idiots Guide to PID controllers.

I'm trying to fiddle the unit to get it to hold rock steady on the selected temperature allowing for the vagaries of a slow cooker and I'm not sure what to expect from raising or lowering the numbers of each adjustment.

Any electronics types out there who can help me?

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I need the Idiots Guide to PID controllers. 

I'm trying to fiddle the unit to get it to hold rock steady on the selected temperature allowing for the vagaries of a slow cooker and I'm not sure what to expect from raising or lowering the numbers of each adjustment.

Dunno if this'll help, but it might explain what its trying to do...

P I D "3 term" Proportional, Integral and Derivative.

It adjusts the output control depending on

Proportional - how far off target it is

Integral - basically how long its been off target

Derivative - the rate of change of the (for you, temperature) measurement

Try using proportional control only, then add a bit of consideration of the integral term, then just a touch (if you feel it worthwhile) of Differential - Diff is the one most likely to have the thing overcorrecting and going all unstable IIRC from a bit of large scale process engineering 30 years ago...

As to translating that into "numbers" for your bit of kit -- all yours, pal !! :smile:

EDIT - PS - don't these things have "autotune" these days?

Edited by dougal (log)

"If you wish to make an apple pie from scratch ... you must first invent the universe." - Carl Sagan

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I need the Idiots Guide to PID controllers. 

I'm trying to fiddle the unit to get it to hold rock steady on the selected temperature allowing for the vagaries of a slow cooker and I'm not sure what to expect from raising or lowering the numbers of each adjustment.

Any electronics types out there who can help me?

I just got the Auber Sous Vide controller yesterday. I'm using it with a Nesco roaster. Used the recomended settings and the temps were too high, then too low, then too high...

Googled and read anything PID 'til i was :wacko:! But it did seem that the "P" was the one to play with. After I lowered that setting it settled right down. :smile:

Hope this helps.

Frank

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Likely your "numbers" are the violence of output response.

Manual tuning, start with way less than maximum violence. 25% or so.

With just P control at 25%, it may respond slowly, but steadily.

Adding violence to P, it will eventually start to overshoot. Adding a bit of I should damp that.

I hope. :cool::smile:

EDIT -- the amount of 'violence' your system can take is going to depend (for the sous-vide example) on things like how the heater wattage relates to the thermal mass of the system...

Edited by dougal (log)

"If you wish to make an apple pie from scratch ... you must first invent the universe." - Carl Sagan

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Likely your "numbers" are the violence of output response.

Manual tuning, start with way less than maximum violence. 25% or so.

With just P control at 25%, it may respond slowly, but steadily.

Adding violence to P, it will eventually start to overshoot. Adding a bit of I should damp that.

I hope.  :cool:  :smile:

EDIT -- the amount of 'violence' your system can take is going to depend (for the sous-vide example) on things like how the heater wattage relates to the thermal mass of the system...

Gee, didn't expect to have to learn all about PID controllers when I bought a "Plug and Play" unit. No it doesn't have any autotune capability. Comes with a chart of recommended settings for different types of cookers. Made the "P" adjustment about 8pm, and it has been stable since 9pm last night, holding right on 141F no variation as long as I leave it alone (Quit peeking, there's nothing to see!).

Nice to know that someone here understands all this stuff.

:smile: eGulleteers are the best.... :smile:

Edited to add:

Of course, I could have just waited til Monday and called for tech support from the manufacturer. But, what fun would that be?

Edited by Quiltguy (log)
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Maybe my memory was a bit off :rolleyes:

This article

http://www.ecircuitcenter.com/Circuits/pid1/pid1.htm

suggests dialling in a little Differential response as the second term, then I as the last one.

Hopefully however, the playful experimentation may have a bit of direction... :biggrin:

"If you wish to make an apple pie from scratch ... you must first invent the universe." - Carl Sagan

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Maybe my memory was a bit off  :rolleyes:

This article

http://www.ecircuitcenter.com/Circuits/pid1/pid1.htm

suggests dialling in a little Differential response as the second term, then I as the last one.

Hopefully however, the playful experimentation may have a bit of direction...  :biggrin:

Thanks guys. I think this last one is the most useful, where it says to set everything to zero and start by adjusting P first.

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  • 4 weeks later...

According to the application notes from Auber Instruments, hot plates work less well than crockpots and rice cookers. Apparently the lack of insulation that pots have on the side make maintaining temperature trickier. They also claim that there is less convection with a hotplate than with the other options.

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According to the application notes from Auber Instruments, hot plates work less well than crockpots and rice cookers. Apparently the lack of insulation that pots have on the side make maintaining temperature trickier. They also claim that there is less convection with a hotplate than with the other options.

Umm, pardon me, but wouldn't cooling at the sides and heating in the middle make for rather excellent convection circulation?

"If you wish to make an apple pie from scratch ... you must first invent the universe." - Carl Sagan

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I don't see their claim about convection on the pdf, where was it?

Lack of insulation might be an issue, but Pielle seems to operate his PIDed stovetop with minimal problems. I'd be curious to see some numbers on bath heterogeneity, as I'm currently trying to figure out the best compromise for a cheap(ish) water bath (leaning towards the stovetop mod).

Martin Mallet

<i>Poor but not starving student</i>

www.malletoyster.com

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According to the application notes from Auber Instruments, hot plates work less well than crockpots and rice cookers. Apparently the lack of insulation that pots have on the side make maintaining temperature trickier. They also claim that there is less convection with a hotplate than with the other options.

I think the problems with hotplates would be a bit different. First of all, an electric hotplate usually is going to be much closer to the maximum wattage; and I've even seen a few that would exceed it.

Second, a hot plate is not necessarily designed to keep a constant temperature like a crock pot or a rice cooker. When it turns on the element gets hot and remains hot even if you cut the power.

Finally, a rice cooker and crock pot have a built in failsafe if the controller fails. When I used the controller I turn the crock pot on high until I reach my target temperature and then switch it to low. Even if the controller fails completely and the crock pot is powered all the time, I'm not in any danger as the crock pot is designed to stay in it's keep warm mode for long periods of time. The same can't be said for the burner on the hotplate. If that think turns on and stays on, you could be in trouble.

The best solution would be an induction device of some sort. But unfortunately, they all seem to have electronic controls so they won't work.

I will attest that the crock pot works great. I made "roast beef" last night for dinner. A top round roast vacuum sealed and put it at 130F for about 20 hours. Seared and sliced thin it was very good. Not quite as flavorful as a rib roast, but pretty good none the less.

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I don't think the second or third concerns are much of an issue:

1) the PID controller takes care of maintaining the constant temperature, and takes into account the relevant variables (latency, output of heater etc..)

2) to the best of my knowledge the dial on the hotplate (or range element) remains functional after modification and can be used to set the maximum output of the unit. Once desired temp is reached, simply dial down: if the control fails you might get a slow simmer but it shouldn't be catastrophic (especially if the vessel you're using has a lid).

Lab hotplates usually incorporate a magnetic stirrer, which could make for a cheap circulation system as well.

Martin Mallet

<i>Poor but not starving student</i>

www.malletoyster.com

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The application notes say the following about hot plates

The heat loss of the  pot causes a larger temperature gradient between the bottom center of the pot  and edges.

This implies that there is not sufficient convection when using a hotplate and pot to keep the temperatures uniform given the rapid heat loss from the sides.

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I got absolutely perfect results with a small 300W immersion heater (USD 10) and a aquarium pump (USD 10) together with the Auber controller. Stable and uniform temperature. 300W was a little too low, so it took some time to bring up to temperature, but once there it was extremely stable.

Unfortunately, the aquarium pump didn't like 82 C over eight hours... :shock:

I think it would work fine up to 60 - 65 C or so.

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I got absolutely perfect results with a small 300W immersion heater (USD 10) and a aquarium pump (USD 10) together with the Auber controller. Stable and uniform temperature. 300W was a little too low, so it took some time to bring up to temperature, but once there it was extremely stable.

Unfortunately, the aquarium pump didn't like 82 C over eight hours...  :shock:

I think it would work fine up to 60 - 65 C or so.

What kind of immersion heater?

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I got absolutely perfect results with a small 300W immersion heater (USD 10) ... 300W was a little too low, so it took some time to bring up to temperature, but once there it was extremely stable.

...

Of course you could just add a second identical heater... :smile:

"If you wish to make an apple pie from scratch ... you must first invent the universe." - Carl Sagan

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