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Old 05-29-2014, 10:19 PM   #61
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Originally Posted by TromboneAl View Post
When I put them in a glass of water, they always agree, no matter what the temperature of the water.

I tried a lot of different positions when measuring the temp of the resting steak, couldn't get them to agree.
Those flexible cables on the probes get flaky. With ours, I need to bake them once in a while, they apparently get moisture in them. Maybe the cable is getting heat from that pan or something, or a flakey connection somewhere.

Ok, a real far out thought - it's pressure on the probe throwing it off. No pressure sitting in liquid.

But you still need a tie breaker thermometer.

-ERD50
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Old 05-29-2014, 11:00 PM   #62
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This is a real engineering puzzle. I love this kind of stuff.

I had a probe going bad. I was not careful with routing the cable through the grill, and a hot spot caused the insulation (teflon?) of the inner coax wire to melt, and the inner wire was shorted to the outer braid. This, I could verify with an ohmmeter.

The sensing element was a thermistor (negative temp coefficient), so a short or low resistance means "off-scale" heat, which is indicated by the display going "HI" for off-scale temperature.

Now, moisture in the cable would also cause a lower resistance due to a partial short, and that also results in a higher temperature reading. I looked at the specs of the ChefAlarm, and it uses a thermistor probe. But how does the cable get wet only while cooking, but not while testing?

Perhaps a replacement probe can be ordered to eliminate this source of error.
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Old 05-30-2014, 09:09 AM   #63
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...
Now, moisture in the cable would also cause a lower resistance due to a partial short, and that also results in a higher temperature reading. I looked at the specs of the ChefAlarm, and it uses a thermistor probe. But how does the cable get wet only while cooking, but not while testing?

Perhaps a replacement probe can be ordered to eliminate this source of error.
Steam, heat releasing moisture that is already there? Some 'gunk' absorbing moisture and becoming conductive? These things are flakey, I have two probes that I check against each other, and check against my hand-held CDN digital.

But as you point out, any material bridging the leads (like moisture), will cause the reading to rise, which is what T-Al seems to see.

I need to look again at getting a few replacement probes for mine. The same company (Polder) has about a dozen different combinations and some have different thermistor values. A new unit might be cheaper than replacement parts though. When I do get a new one, I plan to slip some silicone tubing over it and seal it up on the probe side.

-ERD50
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Old 05-30-2014, 09:14 AM   #64
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I had a cheap wireless thermometer that had other problems, but the temp readings always made sense.

My email to Thermoworks (with photos):

The ChefAlarm is a a quality product but I just cannot get it to work reliably. Here is the review I will write on Amazon after I send it back for a refund. I hope you can give me some tip to get this working, but after five tries, I am going to give up.


Review


Doesn't Work for Me

This is obviously a quality product, but in real world situations, I simply cannot get it to give readings that are remotely correct.


I have checked the calibration of this thermometer along with a traditional, dial instant-read thermometer. In a glass of water, both agree on temperature, whether with an ice bath, boiling water, or heated water somewhere in between. However, when I use it in meat, it gives readings that differ from the traditional thermometer by 30 degrees. I have waited for the thermometers to equilibrate. Experimenting with a thick steak which was "resting" after grilling, I simply could not get the temperature readings to be close to one another.


For example, tonight I put the ChefAlarm probe into a chicken thigh. I was well-inserted, and wasn't touching bone. The probe outside the chicken wasn't touching the pan.


After 23 minutes, the ChefAlarm signaled that the meat had reached a temperature of 169 degrees. I took it out of the oven, and it was obviously totally undercooked. I checked with the CDN thermometer, and that showed that the meat was at 139 degrees. I have had similar results for a whole chick, pork chop, and thick steaks.

I really wanted this thing to work, because I prefer not to have to check the temperature repeatedly. But the way it's working, I cannot trust it. ​I am reluctantly sending it back for a refund.


Their reply:

Al,

We are very sorry you have had a difficult time with your ChefAlarm. We would like to offer to send you, by 2-day shipping, a replacement unit. Before shipping, we will have it certified in our calibration lab against NIST-Traceable temperature standards at 32F and 160F and will supply the test data so you can be absolutely sure that the new ChefAlarm you will be receiving is within specification. We will also include a prepaid return shipping label so you can return the old unit to us so we can test it and find out what was wrong.

As far as trying to explain what went wrong in your use at home, there very well could be something wrong with the unit, although that is not common. If a thermometer tests correctly in ice water and boiling water, it should be giving you an accurate reading in meat. There is nothing about use in a semi-solid that should cause a faulty reading on a thermometer that otherwise works correctly in an ice bath.

Regarding tips for use (that you requested), if you placed the ChefAlarm probe tip in the center of the thickest part of the meat, then that should normally be the lowest temperature in that piece of chicken or meat. In the photos, the thermometers are placed at different angles but we trust that when you made your comparison measurements the tips would have been side by side with the probe shafts at the same angle and depth. I do notice in the first picture that the MAX reading shows 511 F, thus indicating that the probe tip somehow was exposed to a higher temperature than the chicken. Is it possible that the probe tip was at any time pushed past the center and closer to the fire? In your second photo, it looks like you have the probe positioned correctly. We recommend a horizontal penetration with the tip in the vertical and horizontal centers of the thickest part.

The only other comment regarding thermometer use regards the dial thermometers. If you check the CDN instructions at their website, you will find that you must insert their dial thermometer up to the dimple in the shaft. This requires a depth of at least 1.5” to 2” depending on the thermometer model. The mechanical sensor in a dial thermometer is about 3/4” long and if you insert the thermometer to a depth less than the dimple, your thermometer will read low - by as much as several degrees. It is also averaging the temperature over the length up to the dimple whereas the ChefAlarm probe is telling you the temperature of the last 1/4” of its shaft and thus of the meat at that spot only in the meat. In both photos, it looks like the thickness of the meat or chicken is not enough to fully immerse the dial thermometer up to the dimple, and so you are averaging some air temperature along with the meat temperature. The proper way to use a dial thermometer in food is to insert it from the side of the cut, immersing the whole section from the tip to the dimple, trying to center it in the horizontal and vertical centers of the cut. The smaller the cut, the more difficult this will be.

The reason we would like your ChefAlarm back is that you say that the alarm indicated the meat had reached a “done” temperature and that according to what you say, the meat was visibly not done. We are assuming that the probe tip was in that part of the meat that was not done. That would indeed indicate some kind of problem. We want to make sure you have a correctly working ChefAlarm.

If you will accept our offer of a lab-tested new unit, and return the old unit at our expense, then we can be sure that we have delivered what we promise - a thermometer that reads absolutely correctly according to National Standards, within our published specifications. We hope you’ll give us this chance. Sorry again for any inconvenience. Please confirm your acceptance of the offer and we’ll get your new unit on its way.

Thanks,
Chase Draper
Technical Support
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Old 05-30-2014, 09:53 AM   #65
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Originally Posted by TromboneAl View Post
I had a cheap wireless thermometer that had other problems, but the temp readings always made sense.

My email to Thermoworks (with photos):
That was a really well-written response from the company, very professional, informative and polite.

I think this part might be the key, assuming there is no flaw in the unit itself:

Quote:
The only other comment regarding thermometer use regards the dial thermometers. If you check the CDN instructions at their website, you will find that you must insert their dial thermometer up to the dimple in the shaft. This requires a depth of at least 1.5” to 2” depending on the thermometer model. The mechanical sensor in a dial thermometer is about 3/4” long and if you insert the thermometer to a depth less than the dimple, your thermometer will read low - by as much as several degrees. It is also averaging the temperature over the length up to the dimple whereas the ChefAlarm probe is telling you the temperature of the last 1/4” of its shaft and thus of the meat at that spot only in the meat. In both photos, it looks like the thickness of the meat or chicken is not enough to fully immerse the dial thermometer up to the dimple, and so you are averaging some air temperature along with the meat temperature.
But the fact that the chicken was underdone does seem to support that it was closer to 140 than 160F?

More engineering stuff - I've reverse engineered the thermistor specs for my Polder, I just might build/re-build my own industrial strengthprobes.

-ERD50
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Old 05-30-2014, 10:08 AM   #66
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That was a really well-written response from the company, very professional, informative and polite...
+1

I am sure they would love to solve this puzzle (even if it were a competitor probe!), as they could not prove what T-Al did wrong to cause a 30F difference, and the meat being undercooked pointed to the digital thermometer being wrong.

Heck, I almost want to get that mysterious thermometer myself.

I now love to see what they will find.



PS. Thermoworks wrote:
The proper way to use a dial thermometer in food is to insert it from the side of the cut, immersing the whole section from the tip to the dimple, trying to center it in the horizontal and vertical centers of the cut. The smaller the cut, the more difficult this will be.
Yes! Even with the Thermapen, I like to poke edgewise of a thin cut. The small and pointed tip makes this very easy, and I do not even need to hold the cut steady with a tong, as the thin probe is inserted so easily.
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Old 05-30-2014, 10:29 AM   #67
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That was a really well-written response from the company, very professional, informative and polite.
-ERD50
+1 I agree as well. Wow! This was an impressive response from someone who really cares. Clearly they sent your complaint to someone who knows what they are doing, and he took the time to think about it. I am curious as well to learn what they find out in the end.
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Old 06-02-2014, 11:07 AM   #68
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I am impressed with the company. However, note that an earlier request for the some help didn't get a response. It wasn't until I used this subject for my email that I got the response:

Please Avoid Bad Review on Amazon
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Old 06-02-2014, 02:10 PM   #69
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I am impressed with the company. However, note that an earlier request for the some help didn't get a response. It wasn't until I used this subject for my email that I got the response:

Please Avoid Bad Review on Amazon
Sir, I salute you, wonderful way to nicely get their attention.!
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Old 06-03-2014, 09:52 PM   #70
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The replacement unit worked perfectly tonight, although it's possible I just got the probe placements better??

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Old 06-04-2014, 09:50 AM   #71
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Keep testing T-Al. It is a little hard to imagine why the old read the same in water, but not in meat unless it was a placement difference, or maybe some odd parallel path that only happened with the slight pressure from being stuck in meat - but that is hard to picture. And a higher reading does mean a parallel path, not a bad connection - a bad connection would raise resistance which would lower the reading.



Another odd coincidence on my CDN thermometer. Two days ago, DW calls out to me "What happened to my thermometer ? !". So I look at it and it looks like it is reading ~ 110 in a warm room (got into 80's here). I check battery, OK, but replace anyhow. Same. Took out the battery and let the unit dry out for a day in case moisture built up. Still no good. Then I realize the funny "11" digits are really something like an "8" with the horizontal segments missing. Bad LCD or connection?

So I take it apart, and mess it up a bit in the process - turns out you just peel off the front and there are 4 screws underneath holding it to the case, then 4 more to separate the front/back. I separate them, clean everything up with alcohol, including the elasto-meric strip, and re-assemble. Had to add a bit of silicone adhesive to keep the face-plate in place, but it seems to work as good as new.

-ERD50
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Old 06-06-2014, 06:28 AM   #72
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Don't forget the limited edition Thermapen on fire! Just in time for Father's Day. ThermoWorks - Limited Edition Splash-Proof Thermapen®
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Old 06-07-2014, 09:47 AM   #73
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The new one is the same. I think that the problem is that the probe is just too sensitive to position.

Last night I roasted a whole 4.75 pound chicken. I carefully positioned the probe into the middle of the thigh muscle, and baked it until the device beeped at 165 degrees.
I then took the probe out and put it in the breast so that the tip was centered in the breast, and not close to the bone. It then read 145 degrees. I tried a number of positions, and got readings from 145 to 170.

It's just not reliable that way. I can only use it to alert me to when the food is probably ready.

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Old 06-07-2014, 10:12 AM   #74
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The new one is the same. I think that the problem is that the probe is just too sensitive to position.

Last night I roasted a whole 4.75 pound chicken. I carefully positioned the probe into the middle of the thigh muscle, and baked it until the device beeped at 165 degrees.
I then took the probe out and put it in the breast so that the tip was centered in the breast, and not close to the bone. It then read 145 degrees. I tried a number of positions, and got readings from 145 to 170.

It's just not reliable that way. I can only use it to alert me to when the food is probably ready.

...
I think what you are seeing is that the old mechanical style is averaging the reading over a large area, and the new thermo-couple/thermistor-style is giving you very specific area temperatures.

From the sound of it, the probe is actually giving you accurate readings of those areas. They really vary between 145F-170F at the probe tip.

But maybe an average reading is more useful in this case?

I've noticed the same thing when cooking a turkey. I forget the numbers offhand, but they give one target for the breast and another for the thigh, maybe 15F different? Well I could easily get a 15F delta in readings by moving the probe position ever so slightly. It is still largely a guessing game.

If you are shooting for say 165F throughout, unless you cook the chicken for a very long time at a very low temperature (say 200F - but that may not be safe for other reasons, read up before trying this) to allow time for the whole thing to slowly rise to an even temperature, you will have hot/cold spots. Or cook it in liquid or steam for better heat transfer. You could still raise the temperature at the end to brown it.

I assume your chicken was totally defrosted, but still near fridge temperatures of ~ 38-40F? You can see how 300F or 350F air (poor heat transfer in air) will result in a dramatic temperature delta from surface to inside.

edit/add: I'll have to ask DW how she handles chicken. We have whole chickens pretty often, and she will use the oven in winter, grill in the spring-fall, and she just is not a rigorous/precise, procedure-driven type cook, yet, the chicken always comes out done near perfection. Now, if I could just get her to measure and record spices/flavorings, because there is just some magic combination of lemon juice, garlic, salt and maybe a little rosemary and thyme that is just amazing, compared to very, very, very good/great. But she rarely duplicates the amazing, though I am very, very, very happy with very, very, very good/great!

-ERD50
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Old 06-07-2014, 10:50 AM   #75
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It's just not reliable that way. I can only use it to alert me to when the food is probably ready.
That's how I use my remote/long lead probes. They get me in the ballpark. Then I bring in the Thermapen for precise checks.
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Old 06-07-2014, 10:57 AM   #76
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I think what you are seeing is that the old mechanical style is averaging the reading over a large area, and the new thermo-couple/thermistor-style is giving you very specific area temperatures.

From the sound of it, the probe is actually giving you accurate readings of those areas. They really vary between 145F-170F at the probe tip.

But maybe an average reading is more useful in this case?


I've noticed the same thing when cooking a turkey. I forget the numbers offhand, but they give one target for the breast and another for the thigh, maybe 15F different? Well I could easily get a 15F delta in readings by moving the probe position ever so slightly. It is still largely a guessing game.

If you are shooting for say 165F throughout, unless you cook the chicken for a very long time at a very low temperature (say 200F - but that may not be safe for other reasons, read up before trying this) to allow time for the whole thing to slowly rise to an even temperature, you will have hot/cold spots. Or cook it in liquid or steam for better heat transfer. You could still raise the temperature at the end to brown it.

I assume your chicken was totally defrosted, but still near fridge temperatures of ~ 38-40F? You can see how 300F or 350F air (poor heat transfer in air) will result in a dramatic temperature delta from surface to inside.

edit/add: I'll have to ask DW how she handles chicken. We have whole chickens pretty often, and she will use the oven in winter, grill in the spring-fall, and she just is not a rigorous/precise, procedure-driven type cook, yet, the chicken always comes out done near perfection. Now, if I could just get her to measure and record spices/flavorings, because there is just some magic combination of lemon juice, garlic, salt and maybe a little rosemary and thyme that is just amazing, compared to very, very, very good/great. But she rarely duplicates the amazing, though I am very, very, very happy with very, very, very good/great!

-ERD50
I wonder if the good folks at ChefAlarm have considered this, maybe putting in multiple sensors and displaying a range or average. I would have thought that one very accurate point in the center of the meat would be best, but maybe not. Sounds like a new product idea!
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Old 06-07-2014, 11:30 AM   #77
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I wonder if the good folks at ChefAlarm have considered this, maybe putting in multiple sensors and displaying a range or average. I would have thought that one very accurate point in the center of the meat would be best, but maybe not. Sounds like a new product idea!
I was going to suggest that T-Al buy a 12" piece of stainless steel tubing (hobby shop, some HW stores, or on-line), that would provide a tight friction fit on the probe, and cut it to fit. This would increase the thermal mass, and provide more conductivity from the surrounding area (so more of an average reading). But it would also put a slightly bigger hole in the meat.

-ERD50
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Old 06-07-2014, 11:56 AM   #78
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So, the precise pinpoint measurement of the electronic probes works against them. What if an "averaging" thermometer results in an undercooked area, and salmonella hurts you?

I am reminded of a similar problem with high-grade electronic instruments. A fast oscilloscope will show you noise and glitches in a signal that lesser scopes hide. A low-phase-noise spectrum analyzer will show you your sine wave oscillator is not all that stable and is full of frequency jitters. How do we blame better instruments for not lying?
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Old 06-07-2014, 12:04 PM   #79
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Interesting problem, having a more precise measure provides differences in the output. I guess in a way I've seen this. My instant read produces different results on a large piece of meat.
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Old 06-07-2014, 12:28 PM   #80
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So, the precise pinpoint measurement of the electronic probes works against them. What if an "averaging" thermometer results in an undercooked area, and salmonella hurts you?

I am reminded of a similar problem with high-grade electronic instruments. A fast oscilloscope will show you noise and glitches in a signal that lesser scopes hide. A low-phase-noise spectrum analyzer will show you your sine wave oscillator is not all that stable and is full of frequency jitters. How do we blame better instruments for not lying?
+1 Made me smile! Great way to put it!
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