What is the Input Impedance of the PXI-6529

Issue Details

I am evaluating the PXI-6529 for an application I have. I want to confirm if this device is just monitoring the high or low state of a power line, how much current will the device draw or needs to draw to register a high or low? What is its input impedance?

Solution

The PXI‑6529 is an industrial, parallel digital input interface. PXI‑6529 devices are ideal for a variety of applications from automotive design, industrial factory automation, and machine control to aerospace, laboratory research, and biomedical applications.

For industrial digital input devices like the PXI-6529 that operate over a wide voltage range, there's not usually a simple resistor for the input impedance. Instead, there's a transistor that keeps the current more constant over the full operating range.

A simple estimation can be done using the high input voltage range and the maximum input current. The PXI-6529 specifies an input high voltage that goes from 3.2 VDC up to 60 VDC, and a maximum input current of 3.0 mA. Therefore, the lowest input impedance would be 3.2V/3mA = 1.07 kΩ, and the maximum would rise to 20 kΩ at 60V.