Noise and Impedance of MC USB-3105 Analog Output

[Jonathan MA Tech]

What is the impedance on the MC USB-3105 Analog Output channels? I can't find it in any manual or data sheet.

We have a customer that used to use an A/D converter (that we don't know much of anything about) to receive analog voltage signals from our legacy equipment specified to have 100 ohms of impedance on analog output channels. When our customer recently switched to our newer equipment that uses the MC USB-3105 to output analog data for backwards compatibility they started seeing noise on their end.

How might impedance affect the noise on other generic A/D converters? What else should we consider?

[JRys]

Hey Jonathan,

The USB-3105 output impedance is less than an ohm. Impedance is not the issue. Is the connection to the customer's A/D single-ended or differential? Is there or was there isolation. I ask because a ground loop, if not too severe, will make a signal noisy.

best regards,

John

[Jonathan MA Tech]

Both our legacy equipment and new equipment use single ended though I don't know about our customer's system. We have been considering some kind of ground problem.

[Jonathan MA Tech]

We now know that the A/D the customer has is a MC PCI-DAS 6036. Are there any gotchas when interfacing the Analog Output of the USB-3105 with the Analog Input of the PCI-DAQ 6039?

[Fausto]

Hello @Jonathan MA Tech.

Please confirm whether or not your customer has a PCI-DAS6036 board.

https://www.mccdaq.com/pdfs/manuals/PCI-DAS6034-35-36.pdf

The analog input channels on a PCI-DAS6036 board have a 100 GOhm input impedance, while the USB-3105 has a low analog output impedance, < 1 Ohm, as previous posted.

How much noise are you measuring on the analog input channels?

Can you detail your signal wiring connections?

Regards,

Fausto

[Jonathan MA Tech]

It turns out the noise being introduced by this part of the system is less than 20 mV which is insignificant for us. And there was other noise being introduced upstream that we'll be looking at but that's a different discussion.

Thanks for the info, help and asking good questions.