There are people who like to buy new products as soon they come on the market. Then there are people like me on the trailing edge of the adoption curve. Usually this isn't a problem but occasionally I have regrets that I didn't get on board sooner. I recently had such regrets regarding digital thermometers.
Prior to this year I had not needed to take my temperature for a long time as I have been fortunate in having generally good health. However this year because of COVID-19 I have needed to take my temperature many times (among other things my employer requires me to take my temperature before going to work every day). When this started I looked around and discovered I had two thermometers (both of which I believe were gifts from my mother who properly worried that thermometers were the sort of thing that I would neglect getting for myself). One was an old fashioned mercury thermometer probably about 35 years old (the instructions are copyright 1983). The other was a digital thermometer probably about 20 years old give or take (I seem to have lost the instructions). Unfortunately when I tried it the digital thermometer (a K-jump model 720 sold under the Today's Health brand) didn't work. Probably because the battery had died over the many years of disuse.
That left the mercury thermometer. I had some trouble with it too. Mercury thermometers contain a reservoir of mercury at the base of a narrow glass tube with temperature scale markings. When you take your temperature thermal expansion forces some of the mercury up the tube. The higher your temperature the more thermal expansion forcing the mercury higher up into the tube allowing your temperature to be read off. But the mercury doesn't return to the reservoir by itself even after it cools down. The thermometer has to be "shaken down" which means shaking (or jerking) the thermometer in such a way as push the mercury back into the reservoir. Apparently there is a knack to this as I was unable to do it. Fortunately I figured out (or maybe read about on the internet) an alternative. By placing the thermometer in its case, placing the case in a sock and rapidly spinning the sock I was able to force the mercury back into its reservoir. This allowed me to use the mercury thermometer.
Although capable of doing the job (of measuring your temperature) mercury thermometers have some drawbacks. According to the instructions they need to be in your mouth for four minutes to obtain an accurate reading. I am not sure this is really necessary but I didn't experiment with shorter times. The shaking down process consumes some more time. Mercury thermometers are also fragile and a real nuisance if they break because of the mercury. While using the thermometer daily for several months I actually did drop it a few times but fortunately a short distance onto carpet so it didn't break. Still breakage is a constant risk.
So eventually I decided to upgrade to a digital thermometer. I could have tried replacing the battery in the one I had but new ones were cheap enough that this seemed the way to go. I ended up buying a Vicks SpeedRead thermometer (model V912BBUSV1) sold online by Walmart. This was cheap (about $10) and had gotten good customer reviews. I am quite satisfied with it after a few weeks of use. The easy to read display shows your temperature with a resolution of .1 degrees Fahrenheit (the mercury thermometer had similar resolution with scale markings .2 degrees Fahrenheit apart but it was a pain to read). I took my temperature with both a couple of times with good agreement (off .2 degrees one time, 0 degrees the other time). The new digital thermometer is also much faster. I seem to average around 10 seconds before it beeps announcing that it is ready to read. This is a little slower than the advertised 8 second best case but better than the 15 second average case in the fine print. In any case much better than four minutes (or even the 60 seconds claimed by the older model digital thermometer).
All in all in this case the new technology seems far superior and I regret not buying a digital thermometer months earlier (assuming I could have found one in stock, apparently they were in short supply for a while). The main disadvantage of a digital thermometer seems to be that the battery can die. I don't know if the model I bought will provide a reasonable advance warning that the battery is about to die (and this wouldn't help if the battery dies because of long disuse). For this reason I plan to keep the mercury thermometer around as backup. Consumer Reports recommends properly disposing (a bit of a pain in itself) of old mercury thermometers because of the breakage hazard but I don't think the risk is high while it is being stored in its case.
