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ANALOG
INPUT
MULTIPLEXER
V0
V1
V14
V15
DAC
LOAD 1
DAC
LOAD 2
Digital Data
to DACs
12 Bit
DAC 1
12 Bit
DAC 2
Analog
Channel 0
Analog
Channel 1
Analog
Channel 14
Analog
Channel 15
Gain
Amp
To ADC
External Digital and
Power Grounds
AGND
SK1
I/O Connector
Pin 18
Pin 42
16 CHANNEL
DIG GND
FIGURE 3-3
ANALOG INPUT/OUTPUT WIRING
To maintain measurement accuracy, the following precautions must be observed:-
x
Use separate ground wires for analog input, analog output, digital I/O and power lines. Keep
the common ground impedance to a minimum by making the ground point as close as
possible to the /260+ I/O connector or terminal block, and/or use a heavier gauge
wire for the ground connection.
x
If analog input lines are long, each line should be individually shielded to keep noise pick-up to
a minimum. The shield can be the signal return wire in which case it will be connected at each
end, or if twin (signal and return) shielded cables are used, it may be advantageous to connect
the shield at one end only.
x
In order to reduce the absolute gain error to less than one least significant bit all devices
connected to the analog inputs should have a source impedance of less than 15
:
.
x
Input voltages must not exceed the full scale for the selected range.
Содержание PCI230+
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