Thermo Scientific 5028i Instruction Manual page 224

System Description
Hardware
Pressure Board
Battery Board
8-4 Model 5028i Instruction Manual
This PCB assembly is mounted on the floor plate and has five pressure
sensors attached. The pressure board is used to measure the barometric
pressure, differential pressure across the orifice and vacuum under the
filter tap for both channels. All tubing attached to the pressure board is
numbered in case of the need to swap out this board.
This PCB assembly is mounted with two Li batteries to provide a
backup power supply to proportional detectors, and can reduce the
reliable data output time after power up/power interruption for a short
time.
Thermo Fisher Scientific