Analog Inputs and Outputs
ADwin
14
ADwin-Gold II
, Manual February 2013
Fig. 8 – Zero offset in the standard setting of bipolar 10 Volts
Zero offset U
OFF
In the bipolar setting you will get a zero offset, also called offset U
OFF
in the following
text.
For the voltage range of -10V … +10V applies:
U
OFF
= -10V
Gain factor k
v
ADwin-Gold II
has a programmable gain (PGA), which can amplify the input voltage by
the factors 1, 2, 4, or 8. At the same time the measurement range gets smaller by the
corresponding gain factor k
V
(see Annex "
").
Please note that upon applications with k
V
>1 the interference signals are amplified
respectively.
Quantization level U
LSB
The quantization level (U
LSB
) is the smallest digitally displayable voltage difference and
is equivalent to the voltage of the least significant bit (LSB).
The measured value of the 18-bit ADC can be returned with 16 bit or with 24 bit format.
The DAC processes values with 16 bit:
–
16-bit format: The measurement value is given in the lower word, the upper word
is zero.
U
LSB
= 20V / 2
16
= 305.175µV
The same applies for a DAC value.
–
24-bit format: The 24-bit value holds the measurement value in the bits 6…23,
the measurement value being shifted by 6 bits to the left, the bits 0…5 are
always zero.
U
LSB
= 20V / 2
24
= 1.192µV
Fig. 9 – Storage of the ADC/DAC bits in the memory
Conversion Digit to Voltage
DAC
For a DAC:
+10
-10
0
32768
65536
0
[V]
[Digit]
Bit no.
31…24 23…16
15…6
05…00
content
0
18-bit measurement value in bits 6…23
0
0
0
16-bit measurement value in bits 0…15
U
OUT
Digits U
LSB
U
OFF
+
⋅
=
Digits
U
OUT
U
OFF
–
U
LSB
---------------------------------------------
=
