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ADVANCED COMMUNICATIONS & SENSING
USER GUIDE
SX8724SEVK
Evaluation Kit for SX8724S Data Acquisition System
ACS - Revision 1.0 May 2011
© Semtech Corp.
14.1.3 Display Options (right click on the panel)
Copy...
allows the user to copy the display panel into the clip-board. Then the curve can be past in any
other program.
Save Image As...
allows to save the display panel into various common picture formats.
Page Setup...
provides the settings for printing the panel
Print...
allows to select an installed printer and print the display panel.
Show points Values
displays the sample value by pointing on any location on the curve.
Un-Zoom
allows the user to zoom out (with a small step) the display panel if the wheel is not available.
Undo All Zoom/Pan
resets the display range to it’s default values.
14.2
Histogram Panel - Noise Analysis
The distribution of the codes from the acquired signal can be seen on the Histogram panel.
The Histogram graph is computed from a buffer of 1000 consecutive samples. Therefore, the refresh rate is
dependant of the sample rate. If the signal is DC, the distribution width shows the noise.
The samples are coded on 16 bits, if the digital resolution is set to lower than 16bits, some output codes will
never be hit.
14.3
Measured System Performances
The right value for the Measured System Performances is correct only when the DC signal is applied on the
inputs. The values expressed in Volt units [V] are function of the V
REF
voltage set by the user (
) in the GUI.
The measured system performances are computed as follows:
Average
– average of the code distribution measured on a buffer of 1000 samples. If the input is 0V, the
average is equal to the output offset:
Standard Deviation
– the standard deviation is the rms value (Root Mean Square) of the code distribution:
Output noise
– the output noise rms V
N,OUT
is computed with the standard deviation of the code
distribution:
Input referred noise
– V
N,IN
is the rms noise referred to the input. This parameter is computed from the
output rms noise (code) and the total PGA gain:
μ
1
N
----
Σ
samples
(
)
=
LSB
[
]
σ
1
N
----
Σ
sample
average
–
(
)
2
=
LSB
[
]
V
N OUT
,
σ
V
REF
2
16
------------
×
=
Vrms
[
]
V
N IN
,
V
N OUT
,
GDtot
------------------
=
Vrms
[
]
