Facing an issue with the DAQ 6528

[Mapwar96]

Hi everyone,

I’m using the NI PCI-6528 card, which supports both Single-Ended (SE) and Differential (DI) digital input configurations.

Scenario 1: Differential Input (Working)

• DI+ is connected to the positive terminal of the HSD (High-Side Driver).
• DI− is connected to the negative terminal of the HSD.
• In this setup, I can successfully observe the driver's output on both DI+ and DI− pins.

Scenario 2: Single-Ended Input (Not Working)

• DI+ is connected to the positive terminal of the HSD.
• The negative terminal of the HSD is connected to ground.
• In this case, I’m not seeing any signal on the DI+ or DI− pins — both read as 0.

Can someone help me understand why the single-ended configuration isn’t working? Am I missing something in the wiring or configuration?

Thanks in advance!

[ZYOng]

The DI− pin is not just a reference — it’s part of the current loop for the opto-isolator. Even in SE mode, you must provide a return path through DI− for current to flow and activate the input.

You must still connect DI− to ground to complete current loop.