How do I know if my aneroid or mercurial sphyg is out of calibration?
Aneroid sphygs utilize mechanical gears and a mechanical linkage which can wear out or be knocked out of calibration. ADC aneroids are designed to provide a visual indication of accuracy. Our aneroid will require re-calibration if the indicator needle is outside the oval at the bottom of the dial. Unfortunately, when the needle is inside the oval, you can’t be absolutely sure that the gauge is in calibration, unless it is a brand new unit from a reputable manufacturer (that’s because gauges can be tampered with – some more easily than others). As such, it’s a good idea to periodically test the gauge against a unit of known accuracy, or return the unit to ADC for complimentary testing. How often you should perform these accuracy tests depends on many factors, but in general, once a year should be sufficient. Mercurial sphygs utilize gravity, and other than the mercury itself there are no moving parts. So, there is nothing to wear out. A properly designed mercury manometer will be in cal
