Data Translation DT9820 Series, User Manual

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Chapter 2
18
Converting a Twos Complement Code to a Voltage
To convert a twos complement code into a voltage, use the following
formulas:
LSB = FSR
2
N
Code
Offset Binary
= Code
Twos Complement
XOR 2
N-1
Vin = Code
Offset Binary
* LSB + Offset
where,
• LSB is the least significant bit.
• FSR is the full-scale range. For the DT9820 Series, the full-scale
range is 5.0 V for twos complement coding.
• N is the input resolution (24 bits).
• Vin is the analog voltage.
• Code
OffsetBinary
is the raw count used by the software to represent
the voltage in offset binary notation.
• Code
Twos Complement
is the raw count used by the software to
represent the voltage in twos complement notation.
• Offset is the actual minus full-scale value. The minus full-scale
value is
−
2.5 V for twos complement coding.
For example, assume that you are using a DT9822 with a range of
±2.5 V. If the software returns a code of C00000h for the analog input
operation, determine the analog input voltage as follows:
LSB = 5.0 = 0.000000298023
16777216