To summarize, gauge sensors measure in reference to local atmospheric pressure, sealed gauges measure in reference to a specific pressure, and absolute measure in reference to a vacuum. When selecting a sensor from SSI, users should always make sure that its measuring reference is appropriate for the application the sensor is being used in. Use psig for real low pressure ranges, unless installed where ambient pressure conditions are not expected to change. However, psig is limited to 300 psi, whereas sealed units can go to 7500 psi with the SSI transducer.