Agilent Technologies Infiniium 90000 Series Programmer's Manual page 958

34
Waveform Commands
111
110
101
100
011
010
001
000
Figure 9
The graph on the left shows an ADC which has no non- linearity errors.
All of the voltage levels are evenly spaced producing output codes that
represent evenly spaced voltages. In the graph on the right, the voltages
are not evenly spaced with some being wider and some being narrower
than the others.
When you calibrate your Infiniium, the input to each channel, in turn, is
connected to the Aux Out connector. The Aux Out is connected to a 16- bit
digital- to- analog converter (DAC) whose input is controlled by Infiniium's
CPU. There are 65,536 dc voltage levels that are produced by the 16- bit
DAC at the Aux Out. At each dc voltage value, the output of the ADC is
checked to see if a new digital code is produced. When this happens, a
16- bit correction factor is calculated for that digital code and this
correction factor is stored in a Calibration Look- up Table.
958
Ideal ADC Conversion
Normalized Analog Input
ADC Non-linearity Errors for a 3-bit ADC
Agilent Infiniium 90000 Series Oscilloscopes Programmer's Reference
111 Nonlinearity
Errors
110
101
100
011
010
001
000
FS = the full scale
voltage of the ADC
Normalized Analog Input
Non-ideal ADC Conversion