National Instruments PC-LPM-16/PnP - Manual (Page 101)

Appendix D Register-Level Programming
 National Instruments Corporation D-29 PC-LPM-16/PnP User Manual
A/D FIFO Output Binary Modes
The A/D conversion result stored in the A/D FIFO is a 16-bit two’s
complement value. It is made of 13-bit magnitude and 3-bit sign
extension. If the analog input range is unipolar 0 to +10 V or unipolar
0 to +5 V, use the positive values only, making the resolution 12-bit. If
the analog input range is
±
5 V or
±
2.5 V, you can divide the result by
two to yield a 12-bit resolution reading. Also, if you want, the full 13-bit
resolution can be used with the bipolar ranges. Notice, however, that in
Appendix A, Specifications, LSB refers to the least significant bit of a
12-bit conversion value. Table D-2 shows input voltage versus A/D
conversion values for the 0 to +10 V input range. Table D-3 shows
input voltage versus A/D conversion values for -5 to +5 V input range.
Table D-2. Unipolar Input Mode A/D Conversion Values
Input Voltage A/D Conversion Result
Range: 0 to +10 V
(Decimal) (Hex)
0 0 0000
2.5 1,024 0400
5.0 2,048 0800
7.5 3,072 0C00
9.9976 4,095 0FFF
a.Book : l.Appendix D Page 29 Wednesday, November 20, 1996 6:36 PM