AutomationDirect DL205 Manual

DL205 Analog Manual, 7th Edition Rev. D
14-21
Chapter 14: F2-4AD2DA 4-Ch. In / 2-Ch. Out Analog Combination
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Filtering Input Noise (DL250-1, DL260 CPUs Only)
Add the following logic to filter and smooth analog input noise in DL250-1 or DL260 CPUs.
This is especially useful when using PID loops. Noise can be generated by the field device and/
or induced by field wiring.
The analog value in BCD is first converted to a binary number because there isn’t a BCD-to-
real conversion instruction available. Memory location V1400 is the designated workspace
in this example. The MULR instruction is the filter factor, which can be from 0.1–0.9. The
example uses 0.2. A smaller filter factor increases filtering. A higher precision value can be
used, but it is not generally needed. The filtered value is then converted back to binary and
then to BCD. The filtered value is stored in location V1402 for use in your application or
PID loop.
NOTE: Be careful not to do a multiple number conversion on a value. For example, if the pointer method is used to get the
analog value, it is in BCD and must be converted to binary. However, if the conventional method is used to read a value
and the first twelve bits are masked, then it is already in binary and no conversion using the BIN instruction is needed.
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LD
V2000
SUBR
V1400
BTOR
SP1
BIN
Loadsthe analog signal, whichisaBCDvalue
and has beenloadedfromV-memorylocation
V2000,intothe accumulator.Contact SP1 is
always on.
Converts theBCD value in theaccumulator to
binary. Remember,thisinstruction is not
neededifthe analog value is originally
broughtinasabinary number.
Converts thebinar yvalue in theaccumulator
toarealnumber.
Subtractsthe real numberstoredinlocation
V1400 from thereal numberinthe accumulator,
and stores theresultinthe accumulator.V1400
is thedesignatedworkspaceinthisexample.
Multipliesthe real number in the
accumulatorby0.2 (the filter factor),
and stores theresultinthe
accumulator.This is thefiltered value.
OUTD
V1400
ADDR
V1400
MULR
R0.2
OUT
V1402
BCD
RTOB
Adds thereal numberstoredin
locationV1400 to therealnumber
filtered valueinthe accumulator, and
stores theresult in theaccumulator.
Copies thevalue in theaccumulator to
location V1400.
Converts thereal number in the
accumulatortoabinaryvalue, and
stores theresult in theaccumulator.
Converts thebinaryvalue in theaccumulator
to aBCD number. Note: TheBCD instruction
is not needed forPID loop PV (loopPVisa
binary number).
Loads theBCD number filtered valuefrom
theaccumulator intolocationV1402touse in
your applicationorPID loop.

AutomationDirect DL205 Specifications

General

Brand	AutomationDirect
Model	DL205
Category	Controller
Language	English