temp controller accuracy

[sgraham602]

So. just for kicks. i just put another thermometer in my chest freezer to see what the temp was. I have a dual stage temp control set up to keep it at 65 degrees. When i put in my thermometer, it read 74 degrees.

Shouldn't the temp probe on my controller be accurate? This definitely explains why my past 2 batches did not fully attenuate and had very eatery qualities. Should i figure out how much difference there is, and set the controller appropriately?

is this common. I'm a little pissed that I spent big bucks on a dual stage controller only to have the thing hold my beers almost 10 degrees too high.

 

[Double-R]

Which controller are you using...?

 

[Spintab]

Could be where your probe is? Keep it half way up an inch or two off the freezer wall. Are you taking a measurement from the same location as the controller probe?

 

[sgraham602]

taking the same reading as my other probe, although i hang the probe towards the center of the freezer. Would a small fan to circulate the air make any difference??

it is this controller.

http://morebeer.com/view_product/16664

 

[Callacave]

I have the same controller. You need to tape the probe to the fermenter and insulate it. Right now all you're reading are air temps, not the temp of the wort.

 

[sgraham602]

I would think that if it were reading the wort temp, that the controller would be heating and cooling and heating and cooling. fighting itself to maintain temp.

is there a way i can water proof it and submerge it in a glass of water??

 

[sgraham602]

even with it reading the air temps...my controller is reading about 10 degrees off of another thermometer (which i have verified using ice water)

 

[purplehaze]

Why dont you put the temp probe in water as opposed to letting it hang in the air?

I have a cheap aquarium temp controller and the probe sits in a white labs vial filled with water.

 

[Chemkrafty]

Either could be off...calibrate both with a glass of ice water and boiling water if needed. See how much each is off before doing anything. And implement some of the ideas given above to ensure proper temperatures are being read.

 

[Callacave]

It doesn't heat and cool. You'll typically see it cooling during fermentation. You also need to set your deadband properly on the controller. +/- 2F is what I typically use.

 

[Psych]

I have the same controller. You need to tape the probe to the fermenter and insulate it. Right now all you're reading are air temps, not the temp of the wort.

This.

Mine is velcro'd to the side of my fermenters (insulated by bubble wrap) and it reads the temp of the wort perfectly. No need to worry about dangling a probe in a jar of water, no constant cycling.

In fact when I had my probe just dangling, my chamber would cycle so much because the air temp changed so fast. The wort temp holds MUCH longer, and set to .5 of a degree (celcius, albeit) differential, it holds it there perfectly like this.

If my fermentation rages and temps climb, the compressor kicks in to keep things even.

 

[sgraham602]

Totally on board with moving the probe to an area that will better monitor the fermentation temp, but what remains is the accuracy of the probe. If my probe is reading 10 degrees too high, it doesn't matter where I put it. I'll still be getting a false temp.

Is there a way to recalibrate my controller

 

[Callacave]

How can you be sure that the other thermometer you put in there is accurate? You could test both probes in ice water to see how accurate they are and how close they are to each other. I wouldn't write off your Ranco probe yet as faulty. I really think it's just cause you have it dangling in the air.

 

[sgraham602]

looks like i've been trusting the wrong thermometer. my go to wire thermometer (which i have calibrated using ice water in the past) might be wrong. I put the two into ice water. The Ranco read 34 and the other thermometer read 47.

At any rate. what is the best way to set up the ranco. Taped to the carboy, in a glass of water, or one of these do-dads. http://morebeer.com/view_product/16672

 

[Spintab]

I find myself explaining this a lot and it takes a lot of typing so I'll just quote myself from now on...

I don't mean to open a can of worms here but it is better to put the probe in the open air of the freezer and a thermometer either in the wort or on the carboy/bucket. Change the temp of your controller while watching the temp of your wort and adjust accordingly. The thermal capacitance of wort is ginormous compared to air so your freezer will have to make huge temp swings to maintain the wort within the temperature range targeted by your controller. Most temp controllers work within a few degree differential too so the freezer may not turn on until your wort is a couple degrees over your target then the coolant may run through the coils for a bit once the compressor turns off potentially overshooting your target the other way. If you put the controller probe in the air, you are allowing the freezer to make its usual 5-10 degree swings while your wort only changes a half a degree. Granted, this all takes a little extra babysitting in the first few days of a heavy fermentation and your freezer will run for shorter periods more often but it is ultimately more accurate and more consistent.

 

[Brulosopher]

I find myself explaining this a lot and it takes a lot of typing so I'll just quote myself from now on...

I didn't think I would based on the opening sentence... but I agree

 

[Spintab]

I didn't think I would based on the opening sentence... but I agree

Yeah that came across as snotty. Didn't mean it that way. Sorry

 

[Stauffbier]

I've checked the ambient air temp in my chest freezer before as well. Mine also reads as high as 73F sometimes with the controller set to 64F. I'm on the "tape the probe to the bucket" team. One thing to keep in mind is the fact that liquid will retain temps better than air, so after the freezer brings the temp of my wort to 64F it shuts off. As the ambient temp in the freezer starts to rise the temp of my beer stays a little more constant. It does rise, but not as quickly as air. Then when it reaches my "turn on" temp the ambient air rapidly drops well below the 64F that I have the freezer set at. All along the temp of my beer never really fluctuates more than a degree or two.

So, long story short.... If you tape the probe to the bucket your ambient inside of the chamber will have huge temp swings, but your beer won't.

I hope that made sense. Coffee still hasn't quite kicked in....

 

[Brulosopher]

Yeah that came across as snotty. Didn't mean it that way. Sorry

No worries, at least you didn't get all defensive and ****

 

[helibrewer]

looks like i've been trusting the wrong thermometer. my go to wire thermometer (which i have calibrated using ice water in the past) might be wrong. I put the two into ice water. The Ranco read 34 and the other thermometer read 47.

At any rate. what is the best way to set up the ranco. Taped to the carboy, in a glass of water, or one of these do-dads. http://morebeer.com/view_product/16672

^^^^ This. I've always used a thermowell to measure my fermentation temp, however I take a different approach. I keep my chamber around 45 degrees using a probe in a beaker of water. Then I use a FermWarp to heat my fermentor using a probe in the thermowell for control. The down side is that it requires 2 controllers but STC-1000's are cheap, the upside is the kegs in the chamber are serving temp and the fermentor is rock solid on my ferm temp. Cycling 40 watts of FermWrap is more efficient than cycling a compressor.

 

[Stauffbier]

^^^^ This. I've always used a thermowell to measure my fermentation temp, however I take a different approach. I keep my chamber around 45 degrees using a probe in a beaker of water. Then I use a FermWarp to heat my fermentor using a probe in the thermowell for control. The down side is that it requires 2 controllers but STC-1000's are cheap, the upside is the kegs in the chamber are serving temp and the fermentor is rock solid on my ferm temp. Cycling 40 watts of FermWrap is more efficient than cycling a compressor.

So, you're serving kegs and fermenting in the same chamber? That's what I call multi-tasking! I think your situation is a bit unique as compared to most people (or at least I'm assuming that), though.

My thoughts are; in a keezer the probe is better served in a container of water, and in a fermentation chamber the probe is better in a thermowell down in the beer or taped to the fermenter. Just my take on the topic....

 

[Psych]

I find myself explaining this a lot and it takes a lot of typing so I'll just quote myself from now on...

The above quote suggesting putting your probe in the air will offer more accurate temp control over your wort is not accurate, in my opinion. Maybe Spintab hasn't actually done it?

If my chamber is set to a .5(celcius) differential, and I notice absolutely no 'swinging', it should be the same for anyone else, right? Once the cooling stops, it's not going to keep cooling for another half degree across your entire 5 gallons. It takes a good 5 minutes or more to cool that half a degree, so would need another 5 minutes at least to push it to the point of needing to heat up, and 'swing'.

This taping to the side method (providing you're insulating the probe - bubblewrap - from the ambient air) means zero fiddling or need to watch it. Just set to whatever temp you want and walk away.

Bear in mind though that it takes a bit for the probe to equalize out to the wort temp when you first put it on. It's at ambient temp at that point. But once it does equalize, it's money.

 

[Spintab]

The above quote suggesting putting your probe in the air will offer more accurate temp control over your wort is not accurate, in my opinion. Maybe Spintab hasn't actually done it?

If my chamber is set to a .5(celcius) differential, and I notice absolutely no 'swinging', it should be the same for anyone else, right? Once the cooling stops, it's not going to keep cooling for another half degree across your entire 5 gallons. It takes a good 5 minutes or more to cool that half a degree, so would need another 5 minutes at least to push it to the point of needing to heat up, and 'swing'.

I've measured air temps from day one of owning a chest freezer and as of last batch I'm logging ambient, freezer air, and wort temps every 10 seconds to a sql database. My freezer swings about 3-4 degrees per 30 second minimum compressor cycle (usually about once and hour) while my wort swings 0.1 degrees so I haven't had a reason to try a different method. One of these days I'll chunk through a few batches of data and put some solid numbers and a dedicated thread together. My numbers may ultimately prove me wrong, then I'll owe some people some beers. I'm married, I'm good at admitting I'm wrong, believe me.

You say chamber which leads me to believe you are not using a fridge or freezer. Perhaps a son of fermentation chamber? In a chamber this is a different story and putting your probe on or in your wort is fine. They are generally not as well insulated as a freezer and you're usually turning a computer fan on and off. A chamber isn't going to cool beyond the time that fan cuts off like a freezer with cooling coils will. When my freezer cuts off, it still drops a couple/few degrees from the coolant still cold in the coils. Less insulation means the chamber will return to ambient temperature fairly quick rather than holding air temps below your target wort temp like a freezer will. All in all, temperature equilibrium occurs at a faster rate in a chamber so large swings aren't an issue.

Listen, to each his own. I'm not here to say one way is better than the other. If taping your probe to your bucket works for you, then do that. I monitor my temps from my phone and I watch graphs of several hours worth of data as I do so I can babysit the crap out of my beer. I also prefer to let my temps vary a little throughout fermentation. Low in the beginning, then when things settle down slowly raise to help ensure a good finish. If you can't constantly babysit then choosing a static wort temp and going with it may very well be the superior method for you. I'm just saying from a mathematical/scientific/mechanical/thermodynamic standpoint, targeting the air temp of the freezer over the wort has the potential to be more accurate. Targeting wort temp is only as accurate as the minimum differential of your controller. Which one works for you is entirely situational. I mean, is a tenth of a degree, or even a half a degree, ultimately the difference between good and bad beer? Probably not.

Putting the probe in a glass of water would make an excellent compromise though. It's kinda the best of both worlds. I'll be sure to make that part of an official experiment. Until then

 

[afr0byte]

I've measured air temps from day one of owning a chest freezer and as of last batch I'm logging ambient, freezer air, and wort temps every 10 seconds to a sql database. My freezer swings about 3-4 degrees per 30 second minimum compressor cycle (usually about once and hour) while my wort swings 0.1 degrees so I haven't had a reason to try a different method. One of these days I'll chunk through a few batches of data and put some solid numbers and a dedicated thread together. My numbers may ultimately prove me wrong, then I'll owe some people some beers. I'm married, I'm good at admitting I'm wrong, believe me.

You say chamber which leads me to believe you are not using a fridge or freezer. Perhaps a son of fermentation chamber? In a chamber this is a different story and putting your probe on or in your wort is fine. They are generally not as well insulated as a freezer and you're usually turning a computer fan on and off. A chamber isn't going to cool beyond the time that fan cuts off like a freezer with cooling coils will. When my freezer cuts off, it still drops a couple/few degrees from the coolant still cold in the coils. Less insulation means the chamber will return to ambient temperature fairly quick rather than holding air temps below your target wort temp like a freezer will. All in all, temperature equilibrium occurs at a faster rate in a chamber so large swings aren't an issue.

Listen, to each his own. I'm not here to say one way is better than the other. If taping your probe to your bucket works for you, then do that. I monitor my temps from my phone and I watch graphs of several hours worth of data as I do so I can babysit the crap out of my beer. I also prefer to let my temps vary a little throughout fermentation. Low in the beginning, then when things settle down slowly raise to help ensure a good finish. If you can't constantly babysit then choosing a static wort temp and going with it may very well be the superior method for you. I'm just saying from a mathematical/scientific/mechanical/thermodynamic standpoint, targeting the air temp of the freezer over the wort has the potential to be more accurate. Targeting wort temp is only as accurate as the minimum differential of your controller. Which one works for you is entirely situational. I mean, is a tenth of a degree, or even a half a degree, ultimately the difference between good and bad beer? Probably not.

Putting the probe in a glass of water would make an excellent compromise though. It's kinda the best of both worlds. I'll be sure to make that part of an official experiment. Until then

First off, I'd like to say that from my perspective you come off sounding holier than though just because you log your data to a DB.

Anyways, most controllers that people purchase these days (at least the ones available on most homebrew store websites) have a 1 degree differential option. The wort swinging 1 degree either way is most certainly good enough (you even admit that it should be at least). Also, if one tapes their probe to the fermenter then the compressor should kick on less often. It's the compressor kicking on that's the hardest on the the fridge/freezer. I want my freezer to last as long as possible, so I'm going with the option that has it kicking on the fewest number of times. Also, you say that taping on the probe requires more babysitting. I don't see how this could be, at least with a dual stage temperature controller. Certainly when I check my beer multiple times a day the controller is always within a degree of the set point, so that seems pretty easy. If I want to let the beer rise after a couple days I can set the max temp to some higher value (and the min/heating temp higher if I want to force the temp rise). Your method seems like more work to me.

 

[Spintab]

Maaan, I'm not holy, just a programmer by day. It seemed like the natural progression to setup a system to log temps.

 

[Psych]

Wish I had some db temp logging, for sure...anyhow, all's I'm saying here is I can't see how you could get any more accurate to wort temp than having the probe either IN the wort directly, or strapped to the side of the wort container. It's zero fiddling besides setting your initial temp, and if your wort takes off like a banshee and heats up 10 degrees you're covered. It means your chamber doesn't have to warm up from the heat of the wort to reach it's set point.

I do use a home-built chamber, not a son of fermenter thingy but a home built fridge compressor mounted dealie in my own box. I've got wicked insulation on it (3 inches, R15) which keeps so much cold in, EXCEPT on the top where i have this nice double paned glass door from a wine fridge. That glass door gets cold and I think that combined with my lack of any real seal around it (just the old door rubber gasket thingy hitting plywood, though it's a mother of a heavy door) hurts the efficiency of the system a little.

But yeah, right now I have my chamber set to 12.2c, which is 54f or so. My ambient temps in the room are 64'ish. I have two 5G buckets filled with two beers. Both are in the heavy active fermentation stages (day 2 of a very fast start), both thick new krausens bloomed. My chamber is cycling roughly for 2-3 minutes every 30-45 minutes to keep the wort itself in bucket 1 at 54f. Thankfully both buckets are behaving similarly Everytime I check, both are at 54f.

No fuss no muss Now if only I could log this stuff automatically instead of busying myself in the same room and trying to remember how long the thing came on for, and when.

 

[afr0byte]

Maaan, I'm not holy, just a programmer by day. It seemed like the natural progression to setup a system to log temps.

I agree, there's nothing wrong with logging temps. I'm a programmer myself. I was just saying that the way you brought it up it sort of seemed like you were trying to bolster your argument with the fact that you logged data to a db. It came off as very *****ey, especially since your argument appears to be weak.

 

[Stauffbier]

First off, I'd like to say that from my perspective you come off sounding holier than though just because you log your data to a DB.

Anyways, most controllers that people purchase these days (at least the ones available on most homebrew store websites) have a 1 degree differential option. The wort swinging 1 degree either way is most certainly good enough (you even admit that it should be at least). Also, if one tapes their probe to the fermenter then the compressor should kick on less often. It's the compressor kicking on that's the hardest on the the fridge/freezer. I want my freezer to last as long as possible, so I'm going with the option that has it kicking on the fewest number of times. Also, you say that taping on the probe requires more babysitting. I don't see how this could be, at least with a dual stage temperature controller. Certainly when I check my beer multiple times a day the controller is always within a degree of the set point, so that seems pretty easy. If I want to let the beer rise after a couple days I can set the max temp to some higher value (and the min/heating temp higher if I want to force the temp rise). Your method seems like more work to me.

I agree with all of this. Maintaining the longevity of the compressor is also my goal. The way I have my STC-1000 set, my compressor only kicks on about every 60-90 minutes and doesn't run very long when it does. I tape my probe on with good insulation, and I NEVER have to babysit anything. I could literally put a fermenter in the chamber and forget about it for a month (or longer).

 

[Smokingman]

I'm also a programmer by day like Spintab and would like to offer my 2 cents for what's it's worth.

I use a cheap chest freezer with a Johnson Controller for my fermentation. I setup a monitoring system that measured room temperature, freezer air temperature and a probe taped to the side of the carboy.

Here's what I found over several weeks of tests:

• With the controller factory defaults and the probe dangling in air, the temperature swing is as high as 20 degrees F below the set point.
  
• Taping the probe to the carboy reduces the swing to 7 degrees. Insulating the probe didn't seem to make any difference.
  
• Setting the differential on the controller from the factory of 5 to 1 reduced the swing to 3 degrees.
  
• Putting a small fan in the freezer reduced the swing to less than 2 degrees.
  
• During the first few days of fermentation the compressor cycled on every 10 minutes and ran for 3 minutes.
  
• Once fermentation is completed the compressor cycles every hour and also runs for 3 minutes.
  
• All this was with an ambient temperature near the set point of 68F

I hope this information is useful.

 

[Spintab]

Over the past couple days I've run some tests. I'm using a small chest freezer and an arduino based controller. Note, my controller does not use a differential. If it measures a temp over the target temp and it is in cooling mode, it turns on. Once the temp falls below the target, it goes off. No fuzz. The opposite is true when it is set to heating.

Day 1:
- Filled ale pail with 5gal tap water (59f) added ice to drop to 53.5f since the ambient temp in my basement is ~61f I wanted a little separation.
-Left controlling probe in freezer air, placed water/wort probe in a thermowell close to the center of the pail, set controller temp to 54f.
-The water gradually came to a rest at about 53.1f. With the controlling probe in the air, the equilibrium temp will be below the max point on the curve of the freezer air.
- Once the water and air equalized, the freezer was allowed to cycle for about 12hrs. The freezer cycled every 45min - 1hr and stayed on for 30 seconds each time. The freezer air temp swung about 2-3 degrees each compressor cycle while the water temp fluctuated no more than .1f.

Day 2:
- Swapped probes so that the probe in the water was now the controlling probe. The controller code stayed exactly the same. I literally just swapped the probes.
- Set target temp to 53.1 to match where it had settled on the previous day.
- The freezer was allowed to cycle for about 12hrs again. This time it cycled every 1hr - 90min, and stayed on for about 2min each time. The freezer air swung about 4-5 degrees each cycle while the water swung no more than .1f.

In conclusion, with an outside temp just under 10 degrees higher than the target wort temp, and assuming that fermentation has mostly concluded, the difference in accuracy of the two methods is nearly identical. I'd like to try this with a higher difference in temperatures but it will likely result in the same conclusion.

My concern now is this. Once I had cycled the freezer using both methods, I tried dropping the target temp to 52.8 with the controlling probe in the pail. Only a 0.3f drop. Naturally the freezer turned on right away. It took about 3 minutes to cool the freezer to freezing (30f+ swing) and my probe bugged out once it got there so I set the target temp back to 53.1. It took another 2-3 minutes before the water temp fully dropped to 52.8 then continued to drop to 52.1 over the next 40min with the freezing air around it. It has remained there for another 20 minutes and is due to meet the freezer air temp in a few minutes as it raises. It will likely take at least an hour and a half to make it back up to 52.8 again so for more than three hours it will have hovered about a full degree off of the target. It would have been even farther off had I let the freezer continue to run once it hit freezing. If a controller has a half a degree differential, it seems like this would happen every time the freezer cycles. What if the air was cold and you needed to heat the chamber? Would you then have a fire hazard if the heat was left on too long? If the controlling probe was in the air of the freezer I would have set the target a few degrees lower until the water dropped to my real target, then set the target back to about a half a degree above that. A gentle change involving no freezing temps that could freeze my air lock or cause a target to be overshot.

In final conclusion, until that last test I was ready to come on here and say I was wrong (which I am still mostly doing) and put my controlling probe in the wort. But, the final test blew it for me. I don't like the freezer actually reaching freezing temps, nor do I like the way the wort temp continues to drop once the compressor has stopped. The only way I would switch to controlling with the probe in the wort is with some sort of dynamic min/max air temps. Like if you want to go to 54 from 55, not allow the freezer air to drop past 44 or 10 degrees below the target. At that point you'd be using data from both probes to control the system so your venturing towards another method entirely.

So yeah. Not sure where that leaves the debate but I'm tapping out, rescinding my argument for lack of conclusive evidence, and continuing on my merry way. I'll report back in a new thread once I've tested out this new hybrid system. Until then, your minds will remain unblown. Sorry about that.