What thermometer should I buy?

[UncleDave]

I use an infrared thermometer for quick temperature assessments. The beauty is that since it uses a laser, you don't have to sanitize a probe before taking a reading. It reads surface temperatures, so there are times when you would need a probe thermometer as well. Mine reads 1 degree warmer than it should, but it is no big deal. Very handy to have around the house.

Amazon.com: Mastercool MSC52224A Infrared Thermometer: Automotive

 

[Catt22]

I have this multimeter that has a type-k temperature input

Do you think it would be just as good to get a type-k probe from thermapen and use my multimeter as the reader or would the thermapen be a more fast and accurate solution?

Your multi-meter with a type "k" thermocouple is essentially the same as a dedicated temperature meter. You can buy super fast reading replacement thermocouples if desired. The stock probe on my Cole-Parmer unit is plenty fast for my purposes. It's the response time of the probe that will vary with design, but the meters respond almost instantly. They simply monitor the current resistance of the probe. Basically it's a calibrated ohmmeter with a built in algorithm that converts the measured resistance to temperature. It would pay to shop around a little for the best price on a replacement thermocouple. Prices vary widely depending on the source.

 

[Catt22]

I use an infrared thermometer for quick temperature assessments. The beauty is that since it uses a laser, you don't have to sanitize a probe before taking a reading. It reads surface temperatures, so there are times when you would need a probe thermometer as well. Mine reads 1 degree warmer than it should, but it is no big deal. Very handy to have around the house.

Amazon.com: Mastercool MSC52224A Infrared Thermometer: Automotive

I have one of these and found it to be nearly useless for monitoring mash temps. Like you said, it can only read the surface temperatures which can be significantly different than the temperature in the middle of the mash. I use mine to check the output temperature of my CFC and the fermenter before I pitch. They also don't work well on reflective surfaces and the steam from a kettle or mash tun can interfere with the reading. It is a handy tool to have around, but of limited value to me for mash monitoring.

 

[humann_brewing]

Your multi-meter with a type "k" thermocouple is essentially the same as a dedicated temperature meter. You can buy super fast reading replacement thermocouples if desired. The stock probe on my Cole-Parmer unit is plenty fast for my purposes. It's the response time of the probe that will vary with design, but the meters respond almost instantly. They simply monitor the current resistance of the probe. Basically it's a calibrated ohmmeter with a built in algorithm that converts the measured resistance to temperature. It would pay to shop around a little for the best price on a replacement thermocouple. Prices vary widely depending on the source.

Well I came with one but I seriously doubt that it is waterproof. I was thinking about the one that Evan pointed out from the thermopen place but just wanted to know that they were very accurate.

Thanks

 

[Zen_Brew]

Your multi-meter with a type "k" thermocouple is essentially the same as a dedicated temperature meter. You can buy super fast reading replacement thermocouples if desired. The stock probe on my Cole-Parmer unit is plenty fast for my purposes. It's the response time of the probe that will vary with design, but the meters respond almost instantly. They simply monitor the current resistance of the probe. Basically it's a calibrated ohmmeter with a built in algorithm that converts the measured resistance to temperature. It would pay to shop around a little for the best price on a replacement thermocouple. Prices vary widely depending on the source.

Actually the thermocouple does not work on a resistance principle. A thermistor works this way, and an RTD, but not a thermocouple. A thermocouple is a passive device. It is a junction of two dissimiliar metals. The junction is in the tip of the probe. At this junction a current flows due to the different metal properties of each conductor. As the temperature changes the metals expand at different rates, and the amount of current that flows through the junction in millivolts increases as temperature rises and decreases as temperature drops.

Thermocouple are one of the lesser accurate types of industrial probes, but they are one of the more robust, and have a very large usable range. The junction of a type K probe is good for reading temperature to over 1000 degrees C so long as the sheath is rated that high. The base accuracy of a thermocouple is only gauranteed to 2 degrees C or 4 degrees F. In pratice though if you are not using the probe at extreme temperatures they usually stay within a few tenths of a degree. For the temps we measure in brewing they should not deviated more than that unless they are stored in a manner that allows the connectors to corrode.

The probe will not be damaged by getting wet. Unlike resistance probes that have a current sent through them by the meter to read the resistance thermocouples are passive. The current that flows across the junction is a physical property, not an electronic one. So if they get wet there is no sensor to be electrically damaged. If the connector gets wet, simply open it up clean it and dry it and it will work fine the next time you want to use it.

As to the meter. The meter must serve 3 purposes for a thermocouple.
1. It must read the millivolt voltage across the probe junction
2. It must have a circuit to convert the milivolt reading to temperature
3. It must have a reference junction compensator.

It is the accuracy of these 3 operations that determines the accuracy of the meters. Dedicated thermocouple meters generally have a much better reference junction compensation circuit. What this circuit does is this.

When you connect your probe to the meter you actually create a second junction of dissimiliar metals where you just connected the probe. Without a way to compensate for this the electronics in the meter would see an additional temperature (room temp) at the probe connector and add this to the temp at the probe. So if your room is at 70 degrees, and you have the probe in 100 degrees, the meter would report 170 degrees.

A small temp sensor in the meter monitors the temp near the probe connector and subrtracts it from the total reading, basically compensating for room temperature at the junction where the probe connects to the meter.
This is an area where a multimeter is generally a little less accurate than a dedicated thermocouple meter. The quality and placement of the reference junction sensor inside the meter case. This and the fact a thermocouple meter can concentrate just on the accuracy of measuring millivolts with circuits dedicated to that range of inputs vs a multimeter which is a jack of many trades in measuring

Also this means you should not hold the meter tightly in your hand, or you will raise the inside temp of the case above ambient air, and create an incorrect compensation temperature. It also means you should let the meter come to room temperature if it has been removed from a much different temp environment prior to use.

There you go. More than you ever wanted to know about thermocouples.

 

[beerkrump]

WOW! You guys like your thermometers!

I'm way too cheap to fork (thanks for removing that from the censored list) out $100 on a thermometer. I've got one of those big dial analog models. I can calibrate it and if I drop it in the wort, it still works. If I drop it on the floor, it still works. If it rolls on the counter top an rests next to the burner and melts the plastic facing off, it still works. Sure it's a little slow and I can't read to the tenth of a degree, but it works just fine.

 

[Catt22]

Thanks Zen! I stand corrected. That's the best explanation of how they work that I've ever read.

beerkump - That's what I thought about my expensive large analog dial thermometer until it started to read erratically and would not maintain it's calibration. I must have screwed it up somehow, but it shows no outward sign of damage and it was never dropped or handled roughly. My beers kept finishing high and I finally pinned the problem down to problems with that thermometer. Switched to the Cole-Parmer digital and the problem vanished.

 

[humann_brewing]

Holy crap Zen_Brew, are you possibly a electrical engineer or just really have a passion for electric circuitry?

At any rate, if I understood half of that you are saying I should go for a dedicated thermometer like a thermopen opposed to a type-k insert to plug into my multi-meter.

 

[Zen_Brew]

LOL, not an electrical engineer. I'm a calibration technician for some 20 odd years and spent a good bit of time on the temperature end of it, on a high end intrinsic cell RTD calibration system.

I'm not necessarily recommending the thermoPen, just explaning the multimeter and thermocouple that you have. It would work, just may not give you the best accuracy depending on it's specifications and design of the meter. You can't beat a thermocouple for robustness and longevity. You can drop them all day long with no ill effects, sink them in water, put them in a furnace. You'd just be better off with a dedicated thermocouple meter.

I'm not sure having not used one, but my guess is the ThermaPen is based on a thermistor sensor. It is well reviewed here for certain so I don't think you could go wrong with it.

 

[humann_brewing]

LOL, not an electrical engineer. I'm a calibration technician for some 20 odd years and spent a good bit of time on the temperature end of it, on a high end intrinsic cell RTD calibration system.

I'm not necessarily recommending the thermoPen, just explaning the multimeter and thermocouple that you have. It would work, just may not give you the best accuracy depending on it's specifications and design of the meter. You can't beat a thermocouple for robustness and longevity. You can drop them all day long with no ill effects, sink them in water, put them in a furnace. You'd just be better off with a dedicated thermocouple meter.

I'm not sure having not used one, but my guess is the ThermaPen is based on a thermistor sensor. It is well reviewed here for certain so I don't think you could go wrong with it.

What would you suggest for a dedicated thermocouple meter? All I can find at Thermoworks are ones to plugin either through a type-k or type-t connection.
ThermoWorks – Thermocouple Probes.

 

[Zen_Brew]

The plug in ones you are descibing are the type I am referring to.

I would watch the used markets and on Ebay for an older Fluke meter like maybe a Fluke 51, or an older Omega such as one of the HH series like HH81. I am partial myself to buying used but good instruments from Mrf's I am familiar with the track record of. I also know how to adjust most of these units if the calibration has drifted which is a luxury many don't have.

Some of the offerings from Cole Parmer, Barnant, Fisher, VWR, control compay are good as well, but these companies almost all use the same shell meter built overseas and rebrand with their labels. I was on the Cole Parmer site the other day and the nicer units are all over $100 new. Eventually the older models show up on the used market at a nice discount.

As a matter of fact to illustrate the shared overseas design and rebranding. How familiar do these meters look to the ThermoPen people? Not exact, just a bit off on the case
Digital Thermometers - General Purpose And Cole-Parmer Adjustable Angle Thermometer - Cole-Parmer Catalog
http://www.coleparmer.com/catalog/product_view.asp?sku=9038200

There are also many secondary mfr's out there that I am not as familiar with because they are not used very often by commercial users.

 

[humann_brewing]

The plug in ones you are descibing are the type I am referring to.

I would watch the used markets and on Ebay for an older Fluke meter like maybe a Fluke 51, or an older Omega such as one of the HH series like HH81. I am partial myself to buying used but good instruments from Mrf's I am familiar with the track record of. I also know how to adjust most of these units if the calibration has drifted which is a luxury many don't have.

Some of the offerings from Cole Parmer, Barnant, Fisher, VWR, control compay are good as well, but these companies almost all use the same shell meter built overseas and rebrand with their labels. I was on the Cole Parmer site the other day and the nicer units are all over $100 new. Eventually the older models show up on the used market at a nice discount.

As a matter of fact to illustrate the shared overseas design and rebranding. How familiar do these meters look to the ThermoPen people? Not exact, just a bit off on the case
Digital Thermometers - General Purpose And Cole-Parmer Adjustable Angle Thermometer - Cole-Parmer Catalog
Digital Thermometers - General Purpose And Adjustable Angle Thermometer - Cole-Parmer Catalog

There are also many secondary mfr's out there that I am not as familiar with because they are not used very often by commercial users.

I check out my multi meter and I actually have the 81077 model which doesn't give tenths for the temperature

So it looks like I should get a reader anyways but I was wondering I am thinking about getting this model of ph reader that also takes temperature. just wondering how well it would do so. What do you think

http://www.milwaukeetesters.com/pdf/SM102.pdf

Crappy part it that it reads in Celsius only.

 

[sharpstick]

i've used the IR/laser thermometer. it seems like it is reading the steam in a boiling pot. it doesn't read anywhere near 212, so it has its limitations.
i've used a barbecue digital with braided cable, but i have three of those that now are not working right. two of them showed around 130 degrees for ambient temp and one of them is dead. i don't know if they got damaged from submersion or what. i do like being able to leave the probe in the mash or boil, or steep for partial grain batches so i can monitor it constantly. i also have one with a RF remote so i can monitor from in the house.
for what i have paid, i could have bought a thermapen.
thinking of getting one just to calibrate the others if nothing else. does anyone know if it maintains its accuracy or can it be recalibrated if not?
or i might get one of theirs with the submersible probe. i've already guessed my way through two brews without a working thermometer and am getting tired of it.
i can't use the cheap glass ones. they are unreadable.
i've also orderd a 3" analog weldless for my keggle. hopefully i'll be able to read it and it won't get cooked by the flames.