A few days ago I received my poor man's Thermapen. It was a copycat product design to capture the market segment of people felt they cannot justify paying for a near $100 ($96 plus $2.99 shipping) Thermapen. The copycat product is Lavatools' Thermowand for a mere $24.99.
Yes, at just slightly over 1/4 the cost of the Thermapen the Thermowand is too hard to resist. I ordered one. The best thing that happened is it failed right away before I can actually put it to use. Disappointed, I returned it back to Amazon for a full refund. I ordered the Thermoworks' Thermapen.
Today it arrived.
in these two photos you can see the thermapen is much larger than the copycat thermowand; that is a Thai 10 baht coin which is about 1/10 bigger than a US quarter
the probe length is 4.5 inch vs 2.75 inch
I set up an ice bath and a pot of boiling water to check the accuracy. If you ever done this with a very accurate thermometer with fast response (low thermal mass), you would know it is easier said than done if you are expecting fractional degree of accuracy to stabilize. You have to be very mindful of the elevation, where you place the probe tip, and ensure that you are immersing into a spot that you know is truly at boiling point, or true water/ice stabilized zone. I have no doubt with Thermoworks' calibration precision so my tests was just for my own edification.
How fast the reading stabilizes between the real thing and the copycat product is day and night difference. For someone who have worked with thermocouple a lot, I can tell immediately the thermapen's taken pain to design the probe. The thermocouple junction is at the tapper end of the tip and you only need to insert the thin section into the object to get a accurate reading. On the copycat, that fact that it take factor of magnitude to stabilize suggests it is very likely based on RTC sensor because of the much higher thermal mass. Don't get me wrong, for most folks the copycat thermoward at 1/4 the cost is an excellent purchase for used in the kitchen.
In another test, I place the tip under my tongue for a quick accuracy test. It took just a couple of seconds to stabilize which I can see on the display by straining my eyes while the tip is in my mouth. As soon as I pull it out from under the tongue to read like you may naturally do, the reading drops rapidly in degrees in the matter of second. This show how little thermal mass there is. Not very obvious, low thermal mass is extremely important if you try to check the internal temperature of a cake or bread (anything that is fluffy and hence low in relative water content). With a high thermal mass probe, the insertion of the probe robs heat energy from the sample you are measurement can cause the temperature of the contact surface to drop significantly.
When Thermapen first debuted, I didn't recall they have a good marketing. I didn't see any mention that it is based on thermocouple, because it would made a big difference of how I perceived product. I just assumed it is another consumer "toy" thermometer based on thermistor (RTC), or solid state (P-N junction) sensor. Now having seeing it and tested its performance I am very impressed with it. If there is one accurate digital thermometer you own, I would wholeheartedly recommend it. It is a professional measuring instrument - the fact that it comes with a NIST certificate. Typically, name brand thermocouple based thermometer starts at about $250. I recommend a US name-brand like Fluke.
p.s. It may be an urban legend. Someone told me a about an event inside the John Fluke Manufacturing Company decades ago. During a meeting about a marketing promotional campaign. A group of managers was discussing how to promote a product. A smart alec engineer cracked a joke. "why not use the catch phrase of - if it works, it must be a Fluke". Words got around to the top, and the owner didn't share the humor. The engineer was summarily fired.
