Measurement Computing Data Translation DT9857, User Manual

Page: 76 / 192

Chapter 5
76
Analog Input Features
This section describes the following features of analog input (A/D) subsystem on the DT9857
and DT9857E modules:
• Analog input channels, described on this page
• Input ranges and gains, described on this page
• IEPE functions, described on page 77
• Input resolution, described on page 77
• Input sample clock source, described on page 77
• Analog input conversion modes, described on page 78
• Input triggers, described on page 80
• Data format and transfer, described on page 83
• Error conditions, described on page 83
Analog Input Channels
The DT9857-08 and DT9857E-08 modules provides eight analog input channels (channels 0 to
7) and the DT9857-16 and DT9857E-16 modules provides 16 analog input channels (channels 0
to 15). These are single-ended channels; you can connect IEPE sensors to these inputs, if
desired; refer to
page 77 for more information on IEPE functions.
Note: To maintain simultaneous operation, all analog input connections on the DT9857 and
DT9857E modules must have the same lead lengths.
The DT9857 and DT9857E modules use Delta-Sigma analog-to-digital converters (ADCs) that
provide anti-aliasing filters based on the clock rate. These filters remove
aliasing , which is a
condition where high frequency input components erroneously appear as lower frequencies
after sampling.
Using software, you can acquire a single value from a single analog input channel, a single
value from all the analog input channels simultaneously, or multiple values from a one or
more analog input channels, the tachometer, measurement counters, general-purpose
counter/timer, and/or the digital input port. Refer to
“Analog Input Conversion Modes” on
page 78 for more information on specifying and reading data from these channels.
Input Ranges and Gains
The DT9857 and DT9857E modules provide an input range of ±10 V and software-selectable
gains of 1 and 10. This provides effective input ranges of ±10 V (when the gain is 1) and ±1 V
(when the gain is 10).