Absolute or Gauge Pressure/Temperature Data Loggers

Monarch Instrument’s Track-It™ Pressure/Temperature Data Loggers can be ordered with absolute or gauge sensors. (To better understand the difference between the two, check out our Absolute vs Gauge Data Loggers Application Note.)

PSIA (Absolute): Absolute pressure is measured relative to a full vacuum. The pressure of a vessel completely void of any air molecules would be equal to 0 PSIA. Atmospheric pressure (at sea level) is roughly 14.7 PSIA. This means that all Track-It pressure loggers with PSIA sensors will indicate approximately 14.7 PSI at sea level when the pressure port is open to atmosphere (i.e., sitting on a desk or bench during setup).

PSIG (Gauge): Gauge pressure is measured relative to ambient atmospheric pressure. A vessel completely void of any air molecules (at sea level) is roughly -14.7 PSIG, and ambient air pressure is always measured as 0 PSIG. Therefore, all Track-It pressure loggers with PSIG sensors will read 0 when the port is open to atmosphere (i.e., sitting on a desk or bench during setup).