Agilent Technologies DC122 Benutzerhandbuch

The table below summarizes the characteristics discussed in the sections that follow: 

 

Model 
   Agilent # 

DC122  

   U1062A 

4 GS/s 

1 / 1 

512K 

-- 

1K 

DC152  

   U1062A 

4 GS/s 

2 / 2 

256K 

-- 

1K 

DC222   

   U1065A 

8 GS/s 

1 / 1 

1024K 

1G 

125K 

DC252  

   U1065A 

8 GS/s 

2 / 2 

512K 

512M 

125K 

DC282  

   U1065A 

8 GS/s 

4 / 4 

256K 

256M 

125K 

All Acqiris digitizers contain an analog-to-digital conversion (ADC) system that can sample waveforms, in a real 
time sampling mode, at rates from the maximum allowed rate down to 100 S/s (10 ms per point). The sampling rate 
can be programmed and is selectable in a 1, 2, 2.5, 5 sequence (i.e. 1 MS/s, 2 MS/s, 2.5 MS/s, 5 MS/s, 10 MS/s, … 1 
GS/s, 2GS/s, 4 GS/s, 8 GS/s). The maximum sampling rate shown above exploits the possibility of combining 
channels. 

Data from the ADC is stored in on-board acquisition memory. The amount of memory in use for acquisition can be 
programmed and is selectable from 1 point to the full amount of acquisition memory available. 

For technical reasons, a certain acquisition memory “overhead” is required for each waveform, reducing the available 
memory by a small amount. In order to simplify programming, an interface function recommends the best sampling 
rate and the maximum possible number of data points, taking into account the available memory, the requested time 
window, the number of segments (in Sequence mode), as well as the required memory overhead. 

To ensure maximum sampling rate and high timing resolution, we strongly recommend the use of long acquisition 
memories whenever possible. 

Optional Memory is available on most models. It allows the maximum number of segments to be increased 
significantly. However, this memory is divided into 2K sample pages and a segment must start at the beginning of 
the page. Additional memory is used for segment time stamps. These constraints must be kept in mind when trying to 
understand how the driver limits the number of points as the number of segments changes. Furthermore, multi-
segment event readout must read entire pages for each ADC. This can introduce significant overhead for small 
segments and/or when channels are combined. 

Digitizers acquire waveforms in association with triggers. Each waveform is made of a series of measured voltage 
values (sample points) that are made by the ADC at a uniform clock rate. The digitizer can also measure and store 
the arrival time of each trigger using the information from the on board Trigger Time Interpolator (TTI). Readout of 
the individual trigger time stamps makes it possible to determine the time from one trigger to any other trigger. Time 
differences up to 213 days can be measured. The TTI resolution sets the resolution of the trigger time stamps (see 
section  3.3.5  TIMING). To maximize sampling rates and utilize memory as efficiently as possible, the digitizers 
include both Single and Sequential storage modes. For both of these modes the data of all of the active channels is 
acquired synchronously; all of the ADC’s are acquiring data at the same time, to within a small fraction of the 
maximum sampling rate.