i work in the clinical engineering dept. (aka bio med) at a major hospital in northern Indiana and these are good for spot checking but they are not an accuracy device if you want accurate do it manually its the only REAL way to get a good reading. the range of error on these things are +/- 10% so if you are 120 over 80 it could read 132-108 over 88-72 and that is 100% within tolerance