High-Voltage Analog Bus (HVAB)

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Edition Date: April 2015

Part Number: 375472H-01

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The NI SCXI-1127/1128/1129/1175 modules have the capability to route analog signals to their rear connector. If you want to share these analog signals among several modules, use an HVAB adapter such as the NI SCXI-1357/1358/1359. HV8 connectors on the adapters allow you to easily route these signals to a DMM, such as the NI 4060/4070, for measurements. If you are using an SCXI chassis and/or a NI PXI-1010 chassis, use an NI SCXI-1357/1358/1359 with an HV8-BAN4 cable. If you are using an NI PXI-1011 chassis, you only need an HV8-BAN4 cable because the chassis has an integrated HVAB backplane.

  • NI SCXI-1127/1128 Users—When you connect a custom terminal block or cable, it is important that you incorporate the safety interlock scheme into the terminal block/cable. Do this by connecting the +5 V (ISO)_HVAB_EN signal to the +5 V (ISO) signal. These signals are shown in the 1-wire 64×1 multiplexer pinout.
  • NI SCXI-1175 Users—Connecting to the HVAB is only supported in the 2-wire 98x1 multiplexer and 2-wire 95x1 multiplexer topologies.

Derating Modules that Share the HVAB

As a safety precaution, modules that share a common HVAB must be derated to their lowest common voltage rating, even if they do not connect signals to the backplane. The following examples illustrate how to derate your modules.

Example 1

SCXI-1000 chassis

SCXI-1359 2-slot backplane adapter behind Slots 3 and 4

SCXI-1127 (300 V, CAT II) in Slot 4

SCXI-1129 (150 V, CAT I) in Slot 3

Both modules share the HVAB. Therefore, the NI SCXI-1127 must not exceed the rating of the NI SCXI-1129 (150 V, CAT I).

Example 2

SCXI-1000 chassis

SCXI-1359 2-slot backplane adapter behind Slots 3 and 4

SCXI-1127 (300 V, CAT II) in Slot 4

SCXI-1129 (150 V, CAT I) in Slot 2

The SCXI-1127 does not share the HVAB with the NI SCXI-1129. Therefore, the NI SCXI-1127 can operate at the full rating (300 V, CAT II).

Example 3

SCXI-1000 chassis

SCXI-1359 2-slot backplane adapter behind Slots 3 and 4

SCXI-1127 (300 V, CAT II) in Slot 4

SCXI-1190 (30 V, CAT I) in Slot 3

The SCXI-1190 does not have a HVAB connector. Therefore, the NI SCXI-1127 can operate at the full rating (300 V, CAT II).

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