Not getting correct digital output voltage

[IC1]

Hi!

I am using a USB-6009 and have connected the digital output to the analog input (and the digital ground to the analogue ground) in order to test the digital output. The analog input has been tested with a function generator and is measuring correctly.

I find that although I get a signal with a peak-to-peak amplitude of 5V, relative to the ground, the signal changes from -1.45V to 3.55V. I need to generate 5V pulses (0V to 5V relative to ground) in order to control a stepper motor. Please could you let me know how to change this?

Many Thanks

Mark

[JonBowers]

Hi Mark,

When you are connecting an analog input then you can measure it in one of two ways with the USB-6009: Differential or Referenced Single Ended. Differential signals need to be connected to AI0 and AI4. The device will then measure the voltage difference between these two signals. So you need to wire the Digital Gnd into AI4 (pin 30) not the AI Gnd (pin 32). Alternatively you can measure the signal in RSE mode where you only nee to make a connection to AI0 and the device will measure the voltage with respect to its internal ground.

Bellow is a link to the USB-6009 User manual which shoulf explain these connections in more detail.

http://www.ni.com/pdf/manuals/371303h.pdf

Regards

Jon Bowers
Applications Engineer
NI UK & Ireland