22 |
The length of the cable connecting signals to the acquisition
device
is lower than 3 meters
If the signal does not meet the above conditions, it is recommended to use a differential mode
connection to ensure better signal integrity. In single-ended mode, the electrostatic noise and
electromagnetic noise of the coupled input signal connection are more than that in differential
mode.
Non-grounded reference single-ended mode (NRSE) connection methods are shown in Figure 3.6.
Note that the resistance value setting of the grounded resistance is consistent with the that in
difference mode.
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USB-3200
AI
AI-SENSE
AI-GND
Figure 3.6 floating-grounded signal source NRSE input
3.4.
Grounded signal source
The grounded signal source is a signal source connected to the building ground. If the computer is
connected to the same power supply as the signal source, the source is already connected to a
common ground point relative to the device. Instruments and equipment connected to the building
power supply system while with non-isolated outputs belong to this type of signal source.
The potential difference between devices connected to the power supply system of the same
building is usually 1mV to 100mV, but the potential difference may be larger if the distribution
line is not properly connected. If the measurement method is improper, the potential difference
may cause measurement errors. Follow the connection guide for the grounded signal source below
to reduce the grounded potential difference of the measured signal.
Use a differential mode (DIFF) connection
Differential mode connection should be used when any of the following conditions is true:
All analog input channels are connected with valid signal.
Low input signal voltage while high accuracy demanded