NI 6520/6521 User Guide
18
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NI 6521 Isolation Voltages
Cautions
This 150 V Measurement Category II module features 1,400 Vrms isolation
between I/O channels and the backplane, as verified by a dielectric withstand test, 5 s
maximum. Do
not
use this module for connection to signals or for measurements within
Categories III or IV. Do
not
connect to MAINS supply circuits greater than 150 VAC. Refer
to the
section for more information on measurement categories. When
hazardous voltages (>30 Vrms/42.4 V
pk
/60 VDC) are present on any signal, all signals
must be considered hazardous. Ensure that external wiring or any circuits connected to the
device are properly insulated from human contact.
The NI 6521 must be used with special keyed cables and accessories. Refer to the
37-Pin
High-Voltage Accessory Safety Kit Installation Guide
shipped with your device and the
section for more information.
The PCI-6521 must be installed in a PC that adequately grounds the front panel bracket to
the chassis of the PC.
Do
not
remove covers from the NI PCI-6521. Doing so can result in electrical shock or
death.
Use the PXI-6521 in a PXI chassis with properly installed PXI filler panels. Do
not
remove
the filler panels from the NI PXI-6521. Doing so can result in electrical shock or death.
Protecting Inductive Loads
When inductive loads are connected to the relays, a large
counter-electromotive force can occur when the relay disconnects the
circuit. This occurs because of the energy stored in the inductive load.
These flyback voltages can damage the relays and/or the power supply.