FP2 Flow Rate Processor General Information
The FP2 flow rate processor is an electronic manometer capable of measuring two differential pressures at one time,
processing these measurements into various units of measurement, and displaying this data on a terminal in real time.
The FP2 is designed to measure air flow rates in a bounded path using a Static/Pitot velocity probe or similar device.
The FP2 works best in a horizontal position.
Range: 0” – 10”wc working, 11 PSI maximum
Two differential pressure sensors (PS1 and PS2) each have a working range of 10” of water column.
Maximum pressure that can be applied to a pressure sensor port is 11 PSI.
The FP2 provide each pressure sensor 2 automatically selected ranges. 0” – 3”WC and 3” – 10”WC.
NOTE When the FP2 switches ranges from 0 “– 3” to 3” to 10”, there may be a slight “bump” in the pressure readings as
the ranges are switched. Readings at, or very near 3”wc, may be unstable while ranges are switched .
Power: Single 9 volt battery
The FP2 requires a 9 volt battery for operation. Battery life is approximately 19 hours continuous operation.
Terminal: any MS Windows powered PC
The FP2 requires any PC with an MS Windows operating system and a free serial port as a terminal. The terminal works
like the monitor and keyboard of a PC. A terminal allows the FP2 to display data and allows the user to enter data to the
FP2.
Pocket PC require Windows CE 2.11 or later and FPcom for Pocket PC. Other PCs require Windows 95 or later and
FPcom for PCs.
Pressure Sensors PS1 and PS2
The 2 differential pressure sensors are labeled PS1 and PS2 (Pressure Sensor 1 and 2).
Each sensor has 2 ports, a positive port (+) and a negative pressure port (-).
If pressures are measured in relation to atmospheric (one port left open to atmosphere), pressures greater than
atmospheric should be measured on the positive port (with negative port open to atmosphere). Pressures less than
atmospheric should be measured on the negative port (with positive port open to atmosphere).
The FP2 considers pressure only as a positive value even if the measured pressure is less than atmospheric, or in
relation to it’s other port. If the sensors are displaying a negative value while the FP2 is calculating flow rates, they are not
connected correctly. It is normal for the sensors to show negative values while the FP2 is not calculating flow rates.
PS1: While in flow rate calculation mode (CFM/V or mode 1) PS1 is assigned the task of measuring static pressures in
Inches of Water Column. When there is no pressure applied to PS1, the FP2 will not calculate flow rates, and all flow rate
data values will be displayed as 0 (zero), and data columns 1 and 2 will display the actual differential pressure values of
PS1 and PS2 respectfully. The user can see the zero state of PS1 and PS2 while in this state and rezero if needed. It is
normal for the sensors to show a slight negative value while in this state.
The minimum pressure for PS1, the pressure that is required to be present on PS1 in order for the FP2 to begin
calculating flow rates, is by default .05”WC, and can be adjusted by the user with the value for p. If the sensors show a
negative value when the pressure on PS1 exceeds the minimum value, then the connection to the sensor is wrong.
If no pressure is applied to PS1, and there has been no data entry to the FP2 by the user for 3 minutes, the FP2 will enter
a “Sleep” state to conserve battery life.
PS2: is assigned the task of measuring differential pressures from a Static/Pitot velocity probe or similar device, in
Inches of Water Column while in flow rate calculation mode (CFM/V or mode 1). When a minimum pressure has been
applied to PS1, the FP2 will begin to calculate flow rates based on the differential pressure applied to PS2.
Velocity feet per minute rates are calculated as 1096.2 x Square Root(Pv/.075) where Pv is the differential pressure
applied to PS2 in inches of water column, and a standard air density of .075 lbs/Ft^3 is considered.
CFM is calculated as velocity fpm at standard air density x (A/144) where A is the area of the bounded path at point of
measurement in square inches entered by user.
Air Density is calculated as 1.325 x Pb/(T + 460) where Pb is barometric pressure in inches of mercury (entered by the
user) and T is temperature in degrees F (entered by user).
CFM corrected for air density entered by user, is calculated as the CFM at standard air density x Square Root(.075/Air
Density).
Air Density is calculated from the temperature (F) and Barometric pressure (“Hg) entered by the user. Air Density is
calculated as 1.325 x Pb/(T + 460) where Pb is barometric pressure in inches of mercury (entered by the user) and T is
temperature in degrees F (entered by user). Humidity is considered to be 0, or dry air.