Ni 6521 Isolation Voltages; Protecting Inductive Loads - National Instruments NI 6520 User Manual

Cautions
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 Safety Information
hazardous voltages (>30 Vrms/42.4 V
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
NI 6520 Accessory Options
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

NI 6520/6521 User Guide

NI 6521 Isolation Voltages

This 150 V Measurement Category II module features 1,400 Vrms isolation
section for more information on measurement categories. When
section for more information.
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.
/60 VDC) are present on any signal, all signals
pk
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