GBS Elektronik MCA-527 Oscilloscope Mode - Manual (Page 7)

Description of the MCA527 Oscilloscope Mode
2.4.4 Transferring Extended Oscilloscope Data
Since firmware version 12.03 the MCA527 can deliver more data than only the ADC digits. It can additionally
deliver the results of a convolution of the measured data with the trigger filter and the results of a
convolution of the measured data with the main filter.
A prerequisite for getting the extended oscilloscope data is, however, that the resolution = 100ns. In order
that the extended oscilloscope data are calculated, the command CMD_QUERY_OSCI_DATA_EX instead
of CMD_QUERY_OSCI_DATA has to be used. The command has to be passed flags that determine which
calculations shall be done. The results can be read with CMD_QUERY_OSCI_TRIGGER_FILTER_RESULTS and
CMD_QUERY_OSCI_TRIGGER_MAIN_RESULTS.
2.5 Conversion of ADC digits into voltage values
The conversion factor depends on the coarse gain 3 . It is calculated according to the following formula:
conversion factor=
25000 mV
16384⋅coarse gain
The ground line can be determined with assistance of the firmware command
CMD_QUERY_ADJUSTMENT_TABLE. Its result array contains six pairs of calibration values. They are
valid if they are unequal to -1. They are measured with the six real hardware coarse gain settings, always
with Offset DAC = 1024 and Offset DAC = 15360, at open signal input. Based on these values, the ADC
value which corresponds to the ground line can be interpolated.
3 Only the coarse gain values 2, 5, 10, 20, 50 and 100 are really switched by the MCA527 hardware. The
higher coarse gain values are generated by the firmware with real hardware coarse gain = 100.
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