Scaling, Scalingvalue polarity, Maximum and minimum scalingvalues – Rockwell Automation 1771-OFE/B Analog Output Module User Manual User Manual
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Publication 1771Ć6.5.30 - November 1998
Scaling is the conversion of unscaled data to engineering units--such
as gallons/minute, degrees centigrade, and pounds/square inch. You
can use the scaling feature to send the data for each channel to the
module in an optional scaled value representing actual engineering
units. This value is scaled by the module to a proportional binary
value before it is used by the corresponding channel. The resolution
of this data is one part in 4095.
The scaling feature is implemented by entering scaling values in the
data format selected in words 6 through 13 of the BTW.
ScalingValue Polarity
Bits 04 to 11 (04 to 13 octal) of the configuration word (word 5) in
the write block designate positive or negative scaling values
(Figure 3.2). By setting the appropriate negative scaling bit in word
5, you can scale negative data or enable a negative scaling value.
The sign bits are ignored if a corresponding channel is not scaled.
Figure 3.2
Location of ScalingValue Polarity Bits in the Block Transfer Write
Configuration Word
Word/Dec. Bit
15
14
13
12
11
10
09
08
07
06
05
04
03
02
01
00
Word/Octal Bit
17
16
15
14
13
12
11
10
07
06
05
04
03
02
01
00
Word 5
4
4
3
3
2
2
1
1
4
3
2
1
Data Format
Reserved
1 = Binary
0 = BCD
Maximum Scaling Value Polarity
1 = Negative
0 = Positive
Minimum Scaling Value Polarity
1 = Negative
0 = Positive
Data Sign Polarity
1 = Negative
0 = Positive
4 = Channel 4
3 = Channel 3
2 = Channel 2
1 = Channel 1
12883
Maximum and Minimum ScalingValues
Words 6-13 of the write block transfer contain maximum and
minimum scaling values for each channel. Word 6 corresponds to
Channel 1 scale minimum, word 7 to Channel 1 scale maximum,
word 8 to Channel 2 scale minimum, and so on (Figure 3.3).
The maximum and minimum scaling values are the upper and lower
limits for output data. The module’s microprocessor reads these
values and automatically scales output data from the write block
transfer.
Scaling