DN112-06v02
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Output of
Measurements
Measurements include the voltages (including Vmax, Vmin,
Vpp, Vavr, Vrms) and frequency of captured signal.
Measurement output from the SI can be enabled or disabled by
a specific command. This command is described in details in
the section “Commands and Their Returns” below.
Measurement output frame is with the following format.
All voltages are expressed in 16-bit signed integer. Frequency is
expressed in 32-bit unsigned integer.
How to Determine True Voltage
Please note that the byte at offset 4 is called “Voltage Base Unit
(VBU)”. It is a constant number in unit of uV and the value is
20, representing 20uV. The half-word at offset 6 is called
Voltage Resolution (VR), representing voltage per LSB in the
voltage measurements. The value of voltage resolution depends
on sensitivity that was used to capture the data. To calculate
true voltage the following formula can be used:
V = Measurement * VR * 20 (uV)
For example, when sensitivity is set to 2mV/Div the
corresponding VR is 4. If Vmax = 100 this means true
maximum voltage is
100 * 4 * 20 = 8000 (uV) = 8mV
If sensitivity is set 0.5V/Div the corresponding VR is 1000. The
same measurement value (i.e. 100) represents
100 * 1000 * 20 = 2000000 (uV) = 2V
Offset Field Name Size Value
-1 Sync character
1 0xFE
0 Frame ID 1 0xC0
1 Frame Size 2 0x1E ( 30 )
3 Data type 1 0x34
4 Voltage base
unit (VBU) in
uV
1 0x14 ( 20 )
5 Reserved 1 0x00
6 Voltage
resolution in
VBU
2 Sensitivity
dependant
8 Vmax 2
10 Vmin 2
12 Vpp 2
14 Vavr 2
16 Vrms 2
18 Reserved 2
20 Frequency 4
24 Reserved 6
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