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Thermometer wars

Written by glenn

Thermometer Wars

How accurate are the analogue dial type thermomemeters used to measure the correct temperature of steamed/frothed milk?

Good question.

I have tried three different dial type thermometers and all show widely differing temperatures when I tried to measure the boiling point of water. I inserted the stem of each thermomemeter into a pot of boiling water and watched the indicator needle. One measured 90C,one measured 95C and the other measured a perfect 212F.

Hmm...interesting. I did vaguely recall from my high school chemistry class that water boils(depending on altitude) around 100 degrees celsius (212 degrees F), not 90C. I took one of the thermometers back, thinking it was defective and exchanged it for a Taylor generic instant read thermometer with a range from 0F to 212F. The measurement range was a bit wider than I wanted, however that's all there was to choose from at the time. The boiling water test elicited a perfect 212F measurement, however the ice water test indicated a rather high 36F.

So this discovery is not entirely good. If you are aiming for an exact 160F frothing temperature, you could be way off the mark. The manufacturers all claim that the thermometer can be recalibrated by turning the adjustment nut just under the dial. This however just moves the dial face in relation to the needle position - a linear adjustment. So what is accurate for one reading may be wildly off on another. And what are you going to calibrate against?

More research from various sources seems to indicate that for the cheaper thermometers, accuracy is best when the stem is inserted halfway into the liquid. I have found that Taylor thermometers work slightly differently. There is a small dimple (at the 2" mark) on the stem of the Taylor thermometer. According to Taylor, all that is required is to insert the stem into liquid at least 2" deep and you'll be OK. The Taylor pen holder is not just used to carry around your thermometer in your spiffy plastic pocket protector; it is actually a wrench in disguise so that you can turn the adjusting nut if you have to recalibrate the instrument. Curiously, this particular Taylor thermometer is calibrated at the freezing point of water, rather than the boiling point.

Conclusions: Sometimes you do get what you pay for. The inexpensive thermometers appeared not to be accurate when used in a standard 20oz frothing pitcher. The thermometer reading was highly dependent on the depth of the liquid you were measuring.

Recommendation: Don't skimp on quality. The Taylor instrument, responded faster and was far less sensitive to the "depth" problems as described. Accuracy as stated by the manufacturer was plus or minus 1% to 2%. The midpoint of the measuring range being the most accurate.

Glenn S. is a senior financial consultant with a successful firm in Southern Ontario. He works and lives in Waterloo and is the most prolific member of CoffeeCrew.Com.

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