Micromod MOD: Modcell 2050R Users Guide - Manual (Page 193)

IB-23C650
RATIO BIAS CONTROL
A/M RATIO BIAS STATION
The A/M ratio bias station applies a ratio or bias to the process input. The
output of the station is equal to the process x ratio, process ± bias, or process
x ratio ± bias. In this arrangement the PID algorithm is not used. Ratio or
bias values can be entered from either the operators display or through the
remote ratio or bias input (second analog input). In the blending system,
shown in Figure 24, a controller (shown in the shaded area) is used with an
A/M Ratio Bias station. This combination provides two station ratio bias
control with a remote ratio or bias source
which serves as the remote set-point
for the separate dependent variable controller. Both instruments used in a
two-station system must be equipped with an option card to provide the
second analog input.
Figure 24. Two-Stream Blending System Using A/M Ratio Bias Station
Process
Input
Process
Input
Dependent
(Controlled) Flow
Independent (Wild) Flow
Remote
Set-Point
S-1107-251
Controller
A/M Ratio
Bias Station
Flow
Transmitter
2
Flow
Transmitter
1
Remote
Ratio or
Bias
187