JYTEK USB-61210, User Manual

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12 Introduction
Table 1-2: CN1/CN2 I/O Signal Description
1.7 Analog Input Signal Connection
The USB-61210 provides 4 truly differential analog input channels.
These four channels are simultaneous-sampling and support up to
2MS/s per channel. The analog signal can be converted to a digital value
by the A/D converter. To avoid ground loops and obtain more accurate
measurement from the A/D conversion, it is important to understand
the type of signal source and how to connect the signal in differential
mode.
Signal Source Types
Floating
A floating signal source is not connected in any way to the existing
ground system. A device with an isolated output is a floating signal
source. This includes optical isolator outputs, transformer outputs,
and thermocouples.
Ground-Referenced
A ground-referenced signal is connected in some way to the existing
ground system. That is, the signal source is already connected to a
common ground point with respect to the USB-61210, assuming that
the computer is connected to the same power system. Non-isolated
CGND N/A None Chassis ground
GPI<0..7> IGND I
Function Input <0..7>
(see Section 3.1.5: Programmable
Function I/O)
GPO<0..3> IGND O
Function Output <0..3>
(see Section 3.1.5: Programmable
Function I/O)
CONV IGND I External A/D conversion clock
AITG IGND I Digital trigger for analog input
NC NC NC No connection
Signal Reference I/O Description