3.3.4. DP1400 Simultaneous Multibuffer Acquisition and Readout (SMAR)
For this module the internal memory has a
3.3.5. Timing
A
3.3.6. Timebase Range
The timebase range defines the time period over which data is being acquired. For example, the DC110 has a standard acquisition memory of 128 Kpoints and maximum sampling rate of 1 GS/s. Therefore, at the maximum sampling rate, the digitizer can record a signal over a timebase range of up to 130 μs (approx. 130,000 points * 1 ns/point). The timebase range can be adjusted by varying the amount of acquisition memory or the sampling rate of the digitizer.
3.3.7. Combining channels
The DC135/DC140/DC241/DC241A/DC271/DC271A/DC271AR/DP235/DP240/DP1400 digitizers offer the possibility of combining the converters (and their memories) from two or four channels to analyze a single input channel. With this feature the maximum sampling rate and the maximum amount of acquisition memory can be doubled or quadrupled if all of the input channels are not of immediate interest.
3.4.Trigger
Normally the trigger settings applied to the digitizer are used to determine the time at which the device will stop acquiring data. Some models are also capable of a ‘Start on Trigger’ mode of acquisition (see the Programmer’s Guide for further details). The various trigger settings are outlined below.
3.4.1. Trigger Source
The trigger source can be a signal applied to either an Input Channel (internal triggering) or the External Trigger Input. For the DC135/DC140/DC211/DC211A/DC241/DC241A/DC271/DC271A/DC271AR modules, a standardized trigger in signal can also be routed via the PXI Bus Star Trigger line.
Most digitizers provide a separate front panel input BNC connector that can be used as an External Trigger Input. The External Input provides a fully functional trigger circuit with selectable level and slope as for the Internal Triggering source; however it does not include coupling choices nor HF, Window, and Spike Stretcher triggers. The external trigger termination (1 MΩ or 50 Ω) is also selectable on many modules. In modules with this feature, the circuit also provides an overload protection that will automatically switch the coupling from 50 Ω to 1 MΩ if the signal is greater than ±5 V DC.
The
The DP1400 also gives the choice of 50 Ω or 1 MΩ termination impedance for the MCX external input and has diode protection against overload. However, there are no BW limiters and only DC trigger coupling is available.
In all 50 Ω cases a ±5 V limit on trigger signals should be respected, although somewhat higher voltages for short time periods will not damage the unit. For 1 MΩ input signals up to ±100 V (DC + peak AC < 10 KHz) are allowed.
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