Dataman 520 Series - Manual (Page 17)

DATAMAN oscilloscope
User’s Guide
Fig. 2.1.3.1. – Simplified block schematics of the data acquisition
The data from the AD converters are stored in the oscillocope’s onboard memory M.
This memory is addressed by the address counter ADC, which starts to count
immediately after the start of measurement, regardless of trigger event. The
occurrence of a valid trigger event starts the after trigger data counter (ACC). The
Comparator CMP compares the state of ACC with the output of the register (REG),
which contains the data amount acquired after trigger. When the output of ACC
reaches the value written to REG, the comparator produces the signal (done), which
stops both the ADC and ACC counters. The amount of data written after the trigger to
memory depends on the value of REG. The value written to REG controls the relation
of the trigger event and the displayed data. By changing the value of REG it is
possible to display data before, before and after or only after the trigger.
2.2. Hardware description of the DATAMAN 520 family
The DATAMAN 520 series of dual channel digital storage USB oscilloscopes
connect to the computer via USB. They are compatible with both USB 2.0 and USB
1.1. Measurement accuracy is achieved by the stability of the parts used together with
the computing power of the host computer. Calibration data is part of the HW, which
makes it impossible to loose (opposed to the calibration data located on the
diskette/CD). Therefore, it is possible to simply connect the hardware to any computer
(via USB 1.1 or USB 2.0 interface). All you have to do is just install the software.
The DATAMAN 520 series oscilloscopes allow the user to measure waveforms using
two independent channels with a resolution of 8 bits and sensitivity from 10mV/div to
5V/div (80mVfs to 40Vfs) in 9 steps. One division of the oscilloscope screen contains
32 dots. Input impedance matches the oscilloscope standards therefore any regular
oscilloscope probe (with a minimum compensation range of 32pF) can be connected
to the device. The software supports 1:1, 1:10, 1:100 and 1:1000 probes. AC or DC
coupling and the type of probe can be independently selected for each vertical
channel. Any of the inputs can be grounded without disconnecting the probes from the
measured system. Vertical track position can be controlled with an accuracy of 1 pixel
of the oscilloscope screen. Measurement can be triggered from Channel A, Channel B
and/or the External trigger input. Trigger threshold can be set independently for each
channel in the range of the whole oscilloscope screen with a resolution of one pixel.
Threshold of the External trigger input is fixed to about 1.5V (TTL and CMOS
compatible). The DATAMAN 520 series oscilloscopes have the dual level triggering
system, which is further described in chapter 2.1.2. The oscilloscope hardware offers
data acquisition with a maximum rate of 50, 100 or 200MS/s depending on the model.
Therefore it is not possible to sample non-repetitive waveforms faster than every 20,
10 or 5ns (depending on the model). However, thanks to the random sampling
method, it is possible to sample repetitive waveforms with a period of 200, 100 or
50ps (depending on the model), which corresponds with equivalent sampling rates of
5, 10 or 20GS/s. For displaying waveforms acquired using the random sampling
method, we use a system called WCD (Waveform Conformity Detection), which
speeds up display of the changes to the measured waveform.
The oscilloscope hardware can acquire data in one universal mode.
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