VTI Instruments EX1401, User Manual

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VTI Instruments Corp.
40 EX1401 Basic Operation
A
D
C
PLL
CLK=32*2^n*fs
Decimate 2^n
FIR
(Customizable)
(n=1 to 16)
CIC
(/4 to /8192)
CFIR
(/4)
Customizable
Medium Latency
Blind
Downsampling
(/1 to /65536)
2^n*fs
Raw | (Filter = None)
Gain/Offset/
Engineering
Unit Conversion
High Performance
Low Latency
F
IGURE
3-1: ADC
AND
F
ILTER
S
CHEME
It is possible to specify the sampling rate two ways. In the first method you can specify each
parameter of the data decimation chain; including ADC sample clock frequency, filter type and
configuration, downsampling factor etc., to produce a required data output rate. In the second
method you may simply specify the final data sample rate (or the frequency span of interest), and
desired filter type, such that all other dependent parameters will be automatically adjusted, to
produce output at desired sample rate.
The noise floor performance of the system also depends heavily on the decimation rate, since higher
decimation factors will help improve the signal-to-noise ratio. Given below are typical noise level
performance specifications at various input voltage ranges.
Voltage Range Full Scale V
in
Decimation
factor
V
Noise
(uVpp) S/N Ratio (dB)
±100mV 100mV 1
16.20
65.3 dB
±100mV 100mV 10 5.12 75.3 dB
±100mV 100mV 100 1.62 85.3 dB
±100mV 100mV 1000
0.51
95.3 dB
±100mV 100mV 10000
0.16
105.3 dB
±1V 1V 1
65.00
77.4 dB
±1V 1V 10
20.55
87.4 dB
±1V 1V 100
6.50
103.4 dB
±1V 1V 1000
2.06
107.4 dB
±1V 1V 10000
0.65
117.4 dB
±10V 10V 1
966.00
75.6 dB
±10V 10V 10
305.48
85.6 dB
±10V 10V 100
96.60
95.6 dB
±10V 10V 1000
30.55
105.6 dB
±10V 10V 10000
9.66
115.6 dB
T
ABLE
3-2: V
OLTAGE
M
EASUREMENT
N
OISE
P
ROFILE
V
S
. D
ECIMATION
(S
AMPLING RATE
)
O
PEN
T
RANSDUCER
D
ETECTION
/O
VERLOAD
C
ONDITIONS
The EX1401 provides the ability to detect several different signal overload conditions, as well as
several ways to report them. They are reported on a per-channel basis as a 32-bit mask of active
conditions, via the Channel.Overload.Status property. The following bits are supported for the
EX1401:
Bit Mask Name Description