How are blood pressure measuring devices (sphygmomanometers) calibrated?
When I go to the GP, I often get my blood pressure tested. How often do the instruments that are used for this kind of thing get checked out to make sure that they're accurate?
This is very important because if you were to make an error of 5mmHg, because normal blood pressure is about 120 over 80, then you could diagnose someone with high blood pressure and end up being on treatment. The answer is that they're checked regularly and they are calibrated so everyone knows that they are absolutely right.