National Instruments PXI-6521 PXI Digital I/O Module

The National Instruments PXI-6521 (Part Number: 779313-01) is a ±30 VDC, 16-Channel, 8 Relay Outputs, 8 Sink/Source Input, Isolated PXI Digital I/O Module. This module offers industry standard 24 V logic levels and high channel isolation. For added safety, the PXI 6521 provides a keyed connector. The PXI-6521 is a measurement Category II device; thus, it is designed to carry signal voltages ≤ 150 V. However, it can withstand up to 1,500 V surge voltage.

The NI PXI-6521 utilizes positive voltage. A digital high energizes the relay, whereas a low digital de-energizes it. While in the energized state, the COM contact remains lined up to the normally open (NO) contact. In the de-energized state for Form C relays, the common contact remains lined up to the normally closed (NC) contact. The default power-up states for both the Form C and Form A relays are de-energized, which makes contact open at NO and COM. For ensuring power up in a predefined, known state, this model offers user-configurable power-up states. Users can have the power-up states configured using NI-DAQ with LabVIEW.

This Digital I/O Module can monitor changes on all input lines or selected input lines. The user can also program this device to send an interrupt against a change occurring on an input line. As far as the contact rating is concerned, this module offers 60 W/60 VA maximum switching power and 150 VAC maximum voltage. The National Instruments PXI 6521 consumes 100 mA max power while operating at 3.3 V (±5%) and 300 mA at 5 V.