Absolute reference integrity

While possibly the largest majority of pressure measurements in industrial applications are gauge reference mode, there are many critical applications that require an absolute reference. This is commonly the case where venting to an atmospheric pressure for a gauge reference is not possible or practical. In measurements where absolute pressure measurement is required it is vital to have an absolute reference of very high integrity to ensure precision measurement and prevent drift or shift in the output of the sensor.

Absolute reference – When measuring absolute pressures, the pressure reading is referenced to a vacuum.

Reference integrity – The Druck etched cavity piezoresistive sensing element is electrostatically bonded to a glass pillar under vacuum. This, by default, provides an excellent vacuum reference at a value of about 0.1 mTorr, which provides outstanding performance for many pressure applications.

In other pressure sensing technologies, the vacuum reference may be created by evacuating the body tube of the sensor. Aside from this being a relatively large volume there is also the potential of out-gassing of components and epoxies that will degrade the vacuum integrity over time, causing a shift in the output. Any decrease in vacuum (increase in pressure) will also be susceptible to temperature changes.