Athena III User Manual Rev A.03
www.diamondsystems.com
Page
64
14.8
Convert the numerical data to a meaningful value
Once the A/D value is read, it needs to be converted to a meaningful value. The first step is to convert it back to
the actual measured voltage. Afterwards, you may need to convert the voltage to some other engineering units.
For example, the voltage may come from a temperature sensor and the voltage would then need to be converted
to the corresponding temperature, according to the temperature sensor’s characteristics.
Since there are a large number of possible input devices, this secondary step is not included here. Only
conversion to input voltage is described. However, you can combine both transformations into a single formula if
desired.
To convert the A/D value to the corresponding input voltage, use the following formulas.
14.8.1
Conversion Formula for Bipolar Input Ranges
Input voltage = A/D value / 32768 * Full-scale input range
Example:
Given, Input range is 5V and A/D value is 17761.
Therefore,
Input voltage = 17761 / 32768 * 5V = 2.710V.
For a bipolar input range,
1 LSB = 1/32768 * Full-scale voltage.
The table, below, shows the relationship between A/D code and input voltage for a bipolar input range (VFS = Full
scale input voltage).
A/D Code
Input Voltage Symbolic Formula
Input Voltage for 5V Range
-32768
-V
FS
-5.0000V
-32767
-V
FS
+ 1 LSB
-4.9998V
...
...
...
-1
-1 LSB
-0.00015V
0
0
0.0000V
1
+1 LSB
0.00015V
...
...
...
32767
V
FS
- 1 LSB
4.9998V