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<5. Function Test>
TI 34P02K35-02E
Jun. 6, 2018-00
Checking Value of Device Label Variable of Analog Output
Values of device label variables of analog outputs are normally MV values of
NPAS_ID or NPAS_MLD, etc. or values set by an application, and therefore are not
normally entered directly during debugging with I/O in disconnected state. However,
analog output values can be checked using Value of their device label variables in
the same manner as for analog inputs.
Consider an example where the MV value of NPAS_PID is output as device label
variable of an analog output, if the MV value of NPAS_PID is 50%, Value of the
device label variable will be displayed as 16#3000 (=12288).
After changing the status information of a device label variable, change the value of
"Value" of the device label variable.
Reference: Relationship between Analog I/O and I/O Data Processing
POU of NPAS_POU
The relationship between device label variable of analog I/O and I/O data
processing POU of NPAS_POU are described below for reference.
For analog input
PV data measured by field equipment are input to an I/O module of FCN-500 or
FCN-RTU as an electrical signal.
The I/O module converts the electrical signal to UINT data type and writes it to
the Value of the device label variable.
Input data processing POU of NPAS_POU converts the UINT type Value to
normalized data and CDATA_REAL data structure using the input range and
engineering unit.
These data conversions are shown for the following example.
Example:
- Input range 0-200 l/m 4-20mA or 1-5V electrical signal
- NPAS_AI_ANLG (standard analog input POU) is used for input data processing
(1)
Measured
flow rate
(2) Input electrical signal
(3) Conversion by I/O module
(4) Conversion by NPAS_AI_ANLG
4-20 mA 1-5 V
Value of device label variable
Normalized
data
(5) Engineering volume
Hexadecimal
Decimal
Cdata_REAL
0 mA
0 V
16#0000
0
-25%
-50 l/m
0 l/m
4 mA
1 V
16#1000
4096
0%
0 l/m
50 l/m
8 mA
2 V
16#2000
8192
25%
50 l/m
100 l/m
12 mA
3 V
16#3000
12288
50%
100 l/m
150 l/m
16 mA
4 V
16#4000
16384
75%
150 l/m
200 l/m
20 mA
5 V
16#5000
20480
100%
200 l/m

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