Should I replace my temp probe?

[Pyment]

I have noticed that my temp probe doesn't seem to respond very quickly to changes in temp very quickly (I could just lack a little patience).

1) could it help for me to replace it? ie are there real differences between different probes? why would one be better than another?

2) how do I tell the difference between different types of probes?

3) what do "top of the line" probes cost? which are best?

[John F]

Are you sure the temp probe is wrong?

Your roast chamber/bean mass might just be more temp stable than you expect.

I'd try testing before replacing. 

[ButtWhiskers]

With any roaster, the real key is where the thermocouple is placed.  If yours is measuring air temperature rather than the bean mass, you are missing the most critical piece of information.  If it is placed such that it is measuring the temperature of part of the metal structure, you might be getting a slower response and the wrong information to begin with.  You should be measuring the bean temperature and that will not respond quickly to adjustments you make to your flame.  So a slow reaction to adjustments is expected.  If you get a fast response, you are probably measuring the air temperature or part of the roaster that is not fully indicative of the bean temperature.

If your probe is a thermocouple, it will respond in real time to the temperature of its environment (much faster than the beans do), as metals (in general) have a high specific heat.  You probably have a type K thermocouple which is a union of two different metals.  The voltage drop over the junction changes with fluctuations in heat, and the electronics convert the voltage to a temperature reading.  This is why calibration is critical - over time the resistance will shift somewhat, and the instrument that measures it may drift some. 

[Pyment]

I just figured some of out my problem. Tom is wrong.

I had been going by the temps on SM's pictorial guide. I was consistently getting 1C and 2C at 395 F and 437 F consistently. Much lower that his temps. So, I figured that my probe was lagging. I finally noticed after rereading the guide I don't know how many times. Although he has 2c occurring at 465, his description mentions that Northern Italian espresso is roasted just into 2c at 440 F. I guess that means my probe is more accurate than his. Perhaps, after I adjusted my placement of my probe, I have it better than Tom.

Maybe I should shoot him an email that he needs to adjust his probe placement.

Maybe not. Interestingly, my temps are still a bit higher than I was getting on the Diedrich at the SCAA.

The other thing that was bothering me is that when you drop the beans, you are supposed to bottom out and make the turn at 1:30 and temp about 168. If I preheat to a temp that makes the turn at 1:30, the turn is made at about 300. If I go to a lower temp, then the turn is delayed. So I concluded that the probe didn't react quickly enough. Perhaps I am making the turn earlier than I measure at a lower temp.

who knows?

[John F]

Just correlate your #'s to his and call it done....that is my opinion.

Use your #'s for consistency benchmarks.

If you wanted to talk to him directly or replicate something he did just use the "correction" to make sure you are talking about the same #.

 

[Pyment]

Can you believe I didn't use an emoticon where I should have used one to show I was joking about emailing Tom. I have never emailed him before, this would be a heck of a way to introduce myself.


my last roast:
Roast #19
Preheat to 464.
Bottoms out at 1:30 at temp 300 F
turn off heat at temp 338, but rate of rise doesn't slow for another minute which happens to be at 350 F. Heat is turned back on and it slowly rises to a temp of 365 over the next 2 minutes. and resumes usual rate of increase. FC starts at 395 and ends at 415. SC starts at 439 and I stopped the roast at 444 after 30 secs of second.

If I am trying to slow the roast at 370 degrees (to enhance sweetness), Given my usual rate of increase (about 12 degrees per minute at this point of the curve, I need to turn off the heat at 358. If I do that the rate of increase slows to about 5 degrees per minute. So if I turn off the heat for 2 min. It should take 2 min to go from 370 to 380. Is that enough of a pause?

Realizing that my temps are all in Celsius, I would be turning off the heat at 181. I can expect the roast to slow a minute later at a temp of 188 I leave it off for 2 minutes I would turn it back on at 191 and rate of rise would pick back up at 194.

[crholliday]

Is this your commercial roaster?

When we do 5 pound roasts (on our 25 pound roaster) we charge to around 400 F (the range is 30 F degrees depending on a lot of things). Turning point is almost always around 1:05 and usually in the 175 F to 195 F range. 300 F is somewhere between 3:45 and 6:00 depending on bean type, moisture, etc. We hit first right at 390F and rarely hit 2nd but it varies between 428 F and 440 F.

[ButtWhiskers]

I was consistently getting 1C and 2C at 395 F and 437 F consistently.

Excellent - that shows that you are measuring the bean mass and your TC is accurate.

  he has 2c occurring at 465,

at which point beans would be smoldering lumps of ash

If I am trying to slow the roast at 370 degrees (to enhance sweetness), Given my usual rate of increase (about 12 degrees per minute at this point of the curve, I need to turn off the heat at 358. If I do that the rate of increase slows to about 5 degrees per minute. So if I turn off the heat for 2 min. It should take 2 min to go from 370 to 380. Is that enough of a pause?

You could turn off the heat at 351 (that is where caramelization begins) if you want more caramelization.  That buys you another 90 seconds.

[Pyment]

It is my Toper 1K. I think it is a bit underpowered  If I start roasts around 400 I end up with 30 minute roasts.

I think it must be OK. I am not getting any tipping. I think I get a nice even roast. Today's roast (above) is resting and will be my morning cup.

I think most of the heat is conductive, but I suppose there is no way to find out for sure without ruining a batch of beans.

[rasqual]

  he has 2c occurring at 465,

at which point beans would be smoldering lumps of ash

I can confirm this.     

[J.Jirehs Roaster]

  he has 2c occurring at 465,

at which point beans would be smoldering lumps of ash

I can confirm this.     

Me too 

[rasqual]

This coffee roasting method has serious issues.

LOL

[J.Jirehs Roaster]

This coffee roasting method has serious issues.

LOL

Why?!?!  light roast (white ash) no grinding (touch it and you have powder) if I get it all figured... you could take the roasting vessel out of the kiln.... pour the water through and the water will be heated as the pottery cools, water through beans (triggering the a fore mentioned self grinding feature) and ... ta da fresh brewed fresh roasted coffee   

[FinerGrind]

This coffee roasting method has serious issues.

LOL

Why?!?!  light roast (white ash) no grinding (touch it and you have powder) if I get it all figured... you could take the roasting vessel out of the kiln.... pour the water through and the water will be heated as the pottery cools, water through beans (triggering the a fore mentioned self grinding feature) and ... ta da fresh brewed fresh roasted coffee   

This post about roast is my second LOL today.  Funny pix - you should circulate these...

[J.Jirehs Roaster]

This post about roast is my second LOL today.  Funny pix - you should circulate these...

wait till the next open sky roast off    working on my secret weapon... fully solar roaster.... can't say more.. the threads have ears