The accuracy and precision of the thermometer are only parts of the error you are experiencing. One of the most problematic issues with this type of measurement instrument is the response time. If you are measuring meat in the oven, it is great because you stick it in and wait to see what the temperature is. In the case of measuring water coming out of the espresso machine the response time becomes critical. If you let the water run into the cup you are losing quite a bit of heat. You also lose even more while it is sitting in the cup waiting for a measurement. I have seen up to 30 degrees difference. There is an easy way to check for this. Place your thermometer into boiling water, after 60 seconds recorded the measured temperature. Then let the thermometer cool to room temperature. Now get a timer ready and record the time it takes to get from room temperature to the temperature recorded earlier. If this time exceeds 10 seconds you will have a very hard time making any accurate measurements. The Scace device takes about 1 second. A bead probe with a fluke multimeter is close to 1 second. The best way to use the "meat' type thermometers is to measure the water exiting the group head by removing the shower screen and measure the stream of exiting water right at the group. This minimizes the heat loss of sitting in a cup and also traveling through the air.


BillC