Accuracy

Digital consumer products often state resolution which should not be confused with accuracy. Resolution is simply the number of decimal places that the instrument can display and not its accuracy. Consider also a traditional bulb thermometer where the accuracy depends on the scale being correct and aligned correctly as well as your ability to read off the mensicus against that scale.

For consumer products that we offer where the manufacturer makes no claim for accuracy temperature accuracy is likely to be within the range of +/-1C and humidity accuracy in the range of say ±5% within the mid range for any given value might be considered normal. Bear in mind though that an accuracy of ±1ºC could result in a discrepancy of 2ºC between 2 sensors each being within that range but either side of a correct value.

The accuracy of the Barometer reading is generally irrelevant as you will be adjusting it for relative sea level and the altitude figure you set can be used to adjust the barometer pressure. As above it is more important to see trend and linearity with a weather barometer than absolute accuracy.

Generally equipment manufactured to a level of accuracy will be backed by a conformance standard so that you know each and every product is manufactured and factory set to the standard that achieved the stated accuracy i.e. NIST for Davis Instruments. Most such equipment is calibrateable if you wish, something that can be carried out (in the UK) by a UKAS test house. Bear in mind though that there is little point in sending something like a barometer for calibration when it will be returned to you "up hill and down dale" only for you to adjust it for altitude when it arrives back!