Configuration
3/07 UDC3500 Universal Digital Controller Product Manual 113
Function Prompt
Lower Display
Selections or
Range of Setting
Upper Display
Parameter
Definition
CB OUT
CONTROL BLOCK OUTPUT—Output as calculated
by the control block (such as PID A). When using
one of the characterizers, OUTPUT is the output
value after it passes through the characterizer. CB
OUT is the control block output before it passes
through the characterizer.
ATTENTION CB OUT cannot be configured when
Three Position Step Control is used.
PV
PROCESS VARIABLE—Represents the value of
the Process Variable.
DEV
DEVIATION (PROCESS VARIABLE MINUS
SETPOINT)—Represents –100 % to +100 % of the
selected PV span in engineering units.
Zero deviation will produce a center scale (12 mA or
50 %) output. A negative deviation equal in
magnitude to the Output High Scaling Factor will
produce a low-end output (4 mA or 0 %) output. A
positive deviation equal in magnitude to the Output
High Scaling Factor will produce a high-end output
(20 mA or 100 %).
FOR EXAMPLE: Configuration is as follows:
Input 1 = Type T High Thermocouple
PV range = –300 °F to +700 °F
PV span = 1000 °F
Deviation Range = –1000 to +1000 °F = 2000 °F
Second Current Output Low Scale Value = 0.0
Second Current Output High Scale Value = 1000
C2 Range = 4-20 mA
If PV = 500 °F and SP = 650 °F
then Deviation Display = –150 °F, which is
–150 / 2000 = –7.5% of the Deviation Range, so
Second Current Output = 50% – 7.5% = 42.5%
which is 0.425 X 16 mA + 4 mA = 10.8 mA
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