Table of Contents
Advertisement
Appendix C
When the measurement instrument and signal source are at different ground potentials, the
difference in potential is called common-mode voltage. The measurement instrument cannot
discern between the signal and the common-mode voltage believing that the sum of these
voltages is the actual signal. Of course, the common-mode potential is simply an error.
ISO-Channel technology provides common-mode rejection of 150 dB, which contributes an
almost imperceptible error (33.5 million to 1) to Vout. Compare this to traditional data
acquisition measurement instruments, which typically provide only 80 dB of common-mode
rejection and therefore, contribute much more error on the order of 1 part per 10,000.
Simultaneous Architecture
Many measurement instruments on the market today provide multiplexed architectures,
where one A/D is used to measure multiple channels. In this kind of architecture, if one
channel goes down, all channels go down.
ISO-Channel technology, on the other hand, uses a simultaneous architecture, where each
channel has its own dedicated 24-bit Delta-Sigma A/D, as shown in
128
Figure 39: Differential Signals and Common-Mode Voltage
Figure
40.
Advertisement
Table of Contents
