Maximum rating voltage AD3 with BNC adapter

[Olivershado]

Hello,

I'm a newbie with the AD3

Before using my Analog Discovery 3 to measure I would like to a bit more detail about measurement with BNC adapter

On the specs, I saw:

Input range: ±25V (±50V diff)

Input protected: ±50V

BNC adapter is single-ended - probably directly connected to GND. Does it mean that my input range at BNC shouldn't exceed 25V? ( I need to measure 0-30V signal.)

Many thanks for your help

Edited August 9, 2023 by Olivershado

[JColvin]

Hi @Olivershado,

You're correct in that the native input range of the Analog Discovery 3 is ±25V with respect to the device ground which results in a total differential range of 50 V, as noted in the Analog Discovery 3 Resource Center, https://digilent.com/reference/test-and-measurement/analog-discovery-3/start, and it's associated Specifications, https://digilent.com/reference/test-and-measurement/analog-discovery-3/specifications.

It's also worth noting that the Analog Discovery 3 inputs are differential but not floating and that you'll need a ground connection between the AD3 and the DUT to have a common mode. The AD3 is only protected up to ±50 V with respect to its ground (which is going to be the USB ground on your host computer), so you will need a ground connection to the DUT to help ensure this.

You're correct for the BNC adapter that the shielding on the Adapter is connected to the attached Test and Measurement device ground (you can see this on the schematic that is available on the right hand side of its Resource Center here: https://digilent.com/reference/test-and-measurement/bnc-adapter-board/start).

So for it's single ended voltage range, you should stay within the 25 V limit. Technically, you "can" go higher as the AD3 is protected up to 50 V with respect to ground, but you'll be operating outside of the design range and will likely experience signal degradation and attenuation.

To measure a 30 V signal with the BNC Adapter, I would instead use a 10x attenuation setting on a BNC probe and have that setting be matched within the associated Channel options gear dropdown to have hit be appropriately scaled within WaveForms:

Let me know if you have any questions.

Thanks,
JColvin

[Olivershado]

Hi @JColvin,
thank you for so detailed answer! I don't have a question. I'll use 10x attenuation on the BNC probe.
Have a nice day,
Oliver