Function Blocks
3/99 Function Block Reference Guide 43
2.15 CARB Function Block
Description
The
CARB
label stands for
Carbon Potential
. This block is part of the
Loops
category. It looks like this
graphically on the Control Builder.
Function
A combined Carbon Probe and Temperature Probe and PID algorithm determine Carbon Potential of
furnace atmospheres based on a Zirconia probe input.
Input
Probe =
Sensor Input from AI block (0-2 mV)
TEMP
= Temperature Input (
°
F or
°
C) from AI block
%CO =
Percent Carbon Monoxide 1-100%
RSP
= Remote Setpoint Analog Input value in Engineering Units or Percentage (0-1.5)
FFV
= Feedforward value in percentage (0 to 100%) The Feedforward value is multiplied by the
Feedforward Gain, then directly summed into the output of the PID block.
TRV
= Output Track value in Percentage. Output = TRV when TRC is on. (If control output OUT is
connected back to the Track Value Input [TRV], then the Track Command Input [TRC] will function as an
output hold. This may be used where input probes are undergoing burnoff.)
TRC
= Output Track Command [ON, OFF] On-Enables TRV (Mode=Local Override)
BIAS
= Remote Bias value for Ratio PID
SWI
= Switch Inputs (from LPSW function block)
0 = No Change
1 = Initiate Autotuning
2 = Change Control Action (reverse to direct acting or direct to reverse acting)
4 = Force Bumpless Transfer
8 = Switch to Tune Set 1
16 = Switch to Tune Set 2
MDRQI
=External Mode request (typically connected to the MDRQO output of a MDSW function block
that encodes discrete switch inputs).
0 = No Change
1 = Manual Mode Request
2 = Auto Mode Request
4 = Local Setpoint Request
8 = Remote Setpoint Request
BCI
= Back Calculation Input Value—See Note 1.
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