USB-6525 User Guide and Specifications 10 ni.com
Each channel has its own positive and negative terminals. The input range
on the channels is –60 VDC to +60 VDC.
Sensing DC Voltages
The USB-6525 detects a wide range of DC signals, from TTL-like logic
levels to DC power supply levels up to 60 V.
Applying a DC voltage of at least 3.2 V across two input terminals registers
logic high. Applying no voltage or a voltage difference of 1 V or less
registers logic low. DC voltages between 1 V and 3.2 V may not register a
consistent or usable value.
Signal Connection Example
Figure 6 shows signal connections for a power supply and load connected
to an isolated input.
Figure 6. Connecting a Power Supply and Load to the Isolated Input
Caution
Use twisted-pair field wiring to reduce EMC noise.
In Figure 6, the USB-6525 is sensing a powered load that is connected to
the power supply through a switch.
Note Power supplies must be within the USB-6525 device range. Refer to the
Specifications section for information about these ranges.
When the switch is open, no current flows through the load and no voltage
is applied to the load or to the USB-6525 input. The digital logic of the
USB-6525 then registers a logic low for the channel. When the switch is
Isolation
Digital
Logic
Computer
Ground
USB-6525
P1.x+
P1.x–
MOSFET-Based
Current-Limiting
Circuitry
Schottky
Load
+
_
Twisted-Pair
Wiring
Vcc
Vsupply
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