Properly produced aneroid manometers from reputable manufacturers should provide years of dependable service. In fact, at ADC we randomly bench test our manometers for 30,000 pressure cycles to ensure that our devices provide you with unparalleled durability. This destructive test goes well above the 10,000 cycle requirement of the latest ANSI, AAMI, and ISO standards currently required by government regulations.
Current standards for accuracy require that manometers be within +/- 3 mmHg (millimeters of mercury) of the reference standard, or within +/- 3 mmHg or 2% of the reading (whichever is greater) for extended temperature ranges. At ADC, we hold our manometers to even tighter standards and many of our premium aneroid manometers are produced to much more rigorous +/- 2 mmHg standards… 33% more accurate than government requirements.
The "oval" or zero point at the bottom of most aneroids (and all ADC aneroid instruments) measures the equivalent of 6 mmHg across. The purpose of this oval is to help establish a visible cue for the calibration of a manometer. If the needle rests OUTSIDE the oval when the gauge is disconnected from the inflation system, the unit is in need of re-calibration.
Because manometers can be tampered with (and some brands actually facilitate tampering by making them "adjustable"), you can not be 100% sure that a gauge is in calibration just because the indicator needle rests within the zero point oval. The accuracy assurance is only valid for new instruments from ADC, and other reputable manufacturers, on new or factory serviced instruments. This is also why we recommend that you periodically check the calibration of your manometers every 2 years using a reference instrument with a known accuracy. (Note: For instruments with heavy use or older instruments, more frequent recalibration may be required.)
ADC manometers are warranted to remain accurate for 10 years, 20 years, or for life, depending upon the model. Re-calibration will be performed free of charge during the warranty period. Instruments will always be tested free of charge, in or out of warranty.
Unlike aneroid manometers, mercury instruments do not have any mechanical linkages to break, or gears to wear out. As such, once properly calibrated at the factory, mercury manometers will remain accurate so long as the mercury meniscus returns to zero (or within 3 mmHg of 0) when the manometer is removed from the inflation system.
To get the best performance from your mercury manometer, it is important to follow the instructions for cleaning and maintenance of the cartridge tube and filters. This will ensure smooth and even flow of the mercury within the cartridge tube during measurement.