Timing And Triggering; Sample Clock Timebase; External Clock; Digital Triggering - National Instruments SC Express NI PXIe-4339 User Manual

Chapter 2 Using the Module
Any application taking more than 480 μs will fail to close the 2 kHz control loop.
When analyzing the bandwidth of the system, you must consider the group delay of all the
components of the system. When using only the NI PXIe-4339 internal 2 kHz filter, the
bandwidth of the control loop is as follows:
Control Bandwidth
You can increase the bandwidth of the system by either reducing the
Note
application time or by using another filter option with lower group delay.

Timing and Triggering

This section contains information about timing and triggering theory of operation.

Sample Clock Timebase

The ADCs require an oversample clock to drive the conversion. The oversample clock
frequency is greater than the sample rate. On the NI PXIe-4339 modules the oversample clock
is produced from a 100 MHz reference clock. This 100 MHz reference clock can be supplied
either by an onboard oscillator or by the PXI Express backplane 100 MHz clock. Multiple
modules can be synchronized by selecting the PXI Express backplane 100 MHz clock as the
reference clock source for all the modules. Refer to the
for more information.

External Clock

The NI PXIe-4339 ADCs cannot be clocked from external sources such as encoders or
tachometers. However, signal processing features in the Sound and Vibration Measurement
Suite often provide an excellent alternative to external clocking in encoder and tachometer
applications. Visit
ni.com/soundandvibration
Vibration Measurement Suite.

Digital Triggering

You can configure the NI PXIe-4339 modules to start an acquisition in response to a digital
trigger signal from one of the PXI Express backplane trigger lines or the PFI from the front
connector. The trigger circuit can respond either to a rising or a falling edge.
2-30 | ni.com
Application Time ≤ 500 µs - 20 µs
Application Time ≤ 480 µs
= -------------------------------------------------------------------------------------------------------------------------------------- -
Transfer Time
Control Bandwidth
Control Bandwidth = 1613 kHz
1
Application Time
+
1
= -------------------------------------------------------------
20 s 480 s
+ +
Reference Clock Synchronization
for more information about the Sound and
Filter Group Delay
+
120 s
section