Max Machinery 121 INDICATOR - Manual (Page 39)

Principle Of Operation
121-000-350 © 2001 Max Machinery, Inc. Pg 39
7.1 General:
General Operation
The 121 Series 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,
density and viscosity. This information is then used to compute the Corrected Volume Flow or Mass Flow.
7.3 Flow Equations:
Input Flow Computation:
Linear or External SQRT
Input Flow = [% input span • (flow FS - flow low scale)]+ flow low scale
Input Flow Computation:
General Case
Tf = [% input span • (temp FS - Temp low scale)] + temp low scale
RTD Case
Tf = f(measured input resistance)
Input Density Computation:
Temperature Transmitter
density = reference density • (1 - Therm.Exp.Coef. • (Tf-Tref))
2
Density Transmitter
density = [% input span • (density FS - density low scale)] + density low scale
Uncompensated Flow Computation:
Pulse Input; Average K-Factor
Volume Flow = input frequency • time scale factor
K-Factor
Pulse Input; Linear Table
Volume Flow = input frequency • time scale factor
K-Factor (Hz)
Analog Input; Linear
Volume Flow = input flow
Analog Input; Linear Table
Volume Flow = input flow • correction factor (input flow)