Rockwell Automation T8019 Trusted Process Control Algorithm Software Package - Manual (Page 13)

Trusted
TM
Process Control Algorithms T8019
Issue 8 Sep 07 PD-T8019 13
2.2. Analogue Value Clamping
CLAMP
IP
MIN OUT
PV
IP
MAX
LIMIT
The process variable (PV), IP
MAX
, IP
MIN
and OUT values are all of type REAL 2 . The output value
(OUT) is clamped to the range specified by IP
MIN
and IP
MAX
. The LIMIT output, which is of the type
Boolean, is set to TRUE if the clamp is in operation, i.e. LIMIT = IP
MIN
>PV>IP
MAX
.
( ) ( )
MAX MIN
IP , IP PV, Max Min OUT =
If IP
MAX MIN
, the parameters are to be “swapped” and the reversed error count incremented.
Input range parameters (IP
MIN
and IP
MAX
) must be finite, i.e. not ±infinities or NaNs. Behaviour is
undefined for any other values. If PV is a NaN, the function is to set OUT to OUT
MIN
and increment the
“Param” error counter.
2.3. Low Value Select
LVS
OUT PV1
PV2
SEL
The process variables (PV1 and PV2) and the output (OUT) are all REAL values 3 . The output (OUT)
is set to the lower of the two process variable values.
( )
PV2 PV1, MIN OUT =
The SEL output indicates which of the process variables is being used to generate OUT. SEL is of
type BOOLEAN, and is FALSE if using PV1 and TRUE if using PV2.
If PV1 or PV2 is a NaN, the function is to set OUT to PV1, SEL to FALSE and increment the “Param”
error counter. OUT is not a NaN if, and only if, PV1 is not a NaN and finite if, and only if, the lower of
PV1 and PV2 is finite.
2 The standard ISaGRAF LIMIT function provides the equivalent of the CLAMP operation for
integer values (without the limit output).
3 The standard ISaGRAF MIN function provides the equivalent functionality for integer values
(without the SEL output).