Liquid Controls SP3850 - Manual (Page 45)

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SP3850 Flow Computer
7. Principle Of Operation
7.1 General:
The SP3850 Flow Computer uses several internal calculations to compute the
compensated flow based on specific data input. Several computations are performed
to arrive at the uncompensated flow, temperature, pressure, density and viscosity.
This information is then used to compute the Corrected Volume Flow or Mass Flow.
Note concerning Fluid Information
The user will be prompted for Fluid Information during the setup of the instrument.
The unit can store the fluid properties for up to 10 different fluids at one time. See
also Appendix A for common fluid properties for liquids and gases.
7.2 Flow Equations:
Input Temperature Computation:
General Case
Tf = [% input span • (temp FS - Temp low scale)] + temp low scale
RTD Case
Tf = f(measured input resistance)
Input Density Computation:
Density Transmitter
density = [% input span • (density FS - density low scale)] + density low scale
Input Pressure Computation:
General Case
Pf = [% input span • (pressure FS - Pressure Low Scale)] + Pressure Low Scale
Gauge Case
Pf = Pf + Barometric
Manual Case or In Event of Fault
Pf = Pressure Default Value
Fluid Properties:
Liquid Generic Case
liquid density = reference density • (1 - (Therm. Exp. Coef. x 1 e-6 (Tf-Tref)) 2
Liquid API Case
liquid density = reference density • (VCF API2540) • (PCF API)
Gas Case
Pf . Tref Zref
gas density = reference density •
Pref .
•
Tf
•
Zf
Where flowing and reference temperature and pressure are in absolute scale.
General
Operation
Flow Equations