Pilz PSSu E S 2AO U - Manual (Page 15)

Function description
Operating Manual PSSu E S 2AO U(­T)
21423­EN­03 15
4.2.1.3 Manufacturer scaling
Scaling is used to define the offset (zero point compensation) and gain (amplification) of the
digital signal. Offset and gain are entered in the PSSuniversal Configurator as decimal
vaues. The relationship between the signal before manufacturer scaling (x), the signal after
manufacturer scaling (y), offset (b
1
) and gain (a
1
) is a linear equation as follows:
y = (a
1
/ 256
D
* x) + b
1
or
y = (a
1
/ 100
H
* x) + b
1
The term a
1
/ 256
D
corresponds to the amplification factor. With the stated amplification
factor, a
1
is calculated as follows:
a
1
= Amplification factor * 256
D
Amplification by 5 % is therefore:
1.05 * 256
D
= 269
D
Arithmetic examples using decimal values:
Digital value
before manufac­
turer scaling Gain
Manufacturer
scaling Offset
Manufacturer
scaling Amplification Value after
manufacturer
scaling
x a
1
b
1
a
1
/ 256
D
y
1 000 256 0 1 1 000
1 000 512 0 2 2 000
1 000 32 0 0,125 125
1 000 269 500 1,05 1 550
1 000 128 ­50 0,5 450
The module always uses two's complement representation for internal processing, irre­
spective of the configured data format. The values from 0000
H
to FFFF
H
form a number
circle in the two's complement representation. 8000
H
follows 7FFF
H
(= 32 767
D
) and is inter­
preted as the lowest negative number (= ­32 768
D
). 32 767
D
is never exceeded; the value
never falls below ­32 767
D
.
INFORMATION
If 7FFF
H
is exceeded as a result of scaling, unintended values may be set
on the output.
Manufacturer scaling is activated in the default setting. The default value for offset is 0. The
default value for gain is 32
D
(20
H
). That corresponds to amplification factor 0.125 (1/8). This
means that the signal is converted from 15 to 12 Bit for the converter.
4.2.1.4 User scaling
User scaling is an additional scaling level prior to manufacturer scaling. You can use this
scaling to correct local influences. The function is the same as that of manufacturer scaling:
y = (a
2
/ 256
D
* x) + b
2
or
y = (a
2
/ 100
H
* x) + b
2