What is the difference? 
Hint, it's in the sensors.

 

PSIG (Gauge) sensors are the most used by municipalities and in industrial processes whereby barometric pressure has no effect, such as in hydraulic or pneumatic control systems, liquid or gas distribution systems, and liquid level systems that are “open” to atmosphere, etc.

 

PSIA (Absolute) sensors are mostly used in sealed systems or vessels and in sealed, low pressure (or vacuum) systems where slight changes in barometric pressure can significantly affect the system. They are also common in aerospace applications. If you are close to sea level, this would add approximately 14.7 PSI to your measurements.
 
Once you know which your application requires (Absolute or Gauge), the next step is…
 
Choosing a Pressure Range
What is the highest pressure you expect to see? Take that number and choose the next one up! That’s it!
Monarch offers two Track-It Pressure Data Loggers. Both offer the following ranges (Absolute and Gauge):

0-3
0-35
0-150
0-350
0-550
0-2000
0-5800
0-8700 (PSIG only)
0-14,500 PSI (PSIG only)

 
Monarch’s Pressure/Temp Data Loggers have USB connections used for data retrieval.
  
Do you need a NIST Traceable Certificate of Calibration? All pressure loggers go through the same build process using the same components. A NIST (National Institute of Standards and Technology) Certificate validates that the unit meets or exceeds Monarch’s published specifications.
 
The NIST Calibration references 5 test/data points at 0%, 25%, 50%, 75% and 100% of Full Scale and are valid for a period of one year.
 
Monarch’s Pressure Data Loggers are available with 6 PSIA (Absolute) options and 9 PSIG (Gauge) options – and all are available with NIST Calibration.
 
Once you’ve determined Absolute or Gauge, which range, and NIST or not, which Monarch logger is best suited for your application?

 

If you'd like more details, here's our downloadable application note.