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DE-M060304E • DEWE-ORION-1616-10x • Technical Reference Manual • Printing version 1.2.0 • March 19, 2014
DEWE-ORION-1616-10x
3 Theory of operation
3.1 Analog input
3.1.1 Analog input circuit
Figure 10 shows the simplified input circuit of the DEWE-ORION-1616-10x series. The 10 MOhm input termi
-
nation removes signal floating of not connected input signals. The pre-filter removes noise from the input and
protects the PGA against over voltages. This programmable gain amplifier with the steps 1, 2, 4 and 8 allows
four different input ranges from ±1.25 V to 10 V. Especially in sensed mode configuration the differential am
-
plifier removes offset errors caused by ground loops.
CH x
10 M
22 pF
3k9
from sense amplifier
Programmable
gain amplifier
Input
termination
Differential
amplifier
Lowpass
filter
Pre-filter
A/D converter
ADC
Figure 10: DEWE-ORION-1616-10x input circuit
Please note that in sensed mode configuration the input ranges of the whole channel group related to the
sense amplifier (Ch0 to Ch7 and Ch8 to 15) have to be the same!
The overall bandwidth is shown below. The analog bandwidth is defined by the following low pass filter.
-80
-60
-40
-20
0
1
10
100
1000
10000
Frequency [kHz]
Am
pl
itude
[d
B]
-30
-20
-10
0
10
100
1000
Frequency [kHz]
Am
plit
ud
e
[d
B]
Figure 11: Overall bandwidth and bandwith with lowpass filter
3.1.2 Analog to digital conversion
The DEWE-ORION-1616-10x series is based on successive approximation analog to digital converter. At
each sample the current analog value is tracked by an internal sample & hold circuit for the duration of the
conversion time. During this conversion time this analog value is compared bit by bit with the reference volt-
age for getting the digital value. This architecture allows also multiple board operation like external clocking
from 0 samples/sec to the maximum sample rate of 100 kSamples/second.
3.1.3 Output data format
Each analog channel is transferred as a standard twos complement 16-bit value represents the analog
input value. 1 LSB equals the whole input range / 2
16
. This is possible due to the hardware offset and gain
correction at the DEWE-ORION-1616-10x. The PCI-bus width is 32-bits. Because of that the channels
are transferred always in pairs to the DMA controller. That means Ch0 is always combined with CH1, Ch2
with Ch3 and so on.
3.1.4 Calibration
Your DEWE-ORION-1616-10x is shipped with a calibration certificate. Typically a recalibration is required
every year. The calibration constants are stored in the on-board EEPROM. The calibration can only be done
with an optional available calibration kit or you can send the DEWE-ORION-1616-10x back to DEWETRON
for recalibration.
Содержание DEWE-ORION-1616-10 Series
Страница 56: ...C2 Notes...
