How to measure output voltage of B200?

[Nate Duong]

Hi,

I am a new student and trying to to measure the power and voltage output from B200 SDR device (https://www.ettus.com/content/files/b200-b210_spec_sheet.pdf) using oscilloscope (TDS3000 Series: https://www.atecorp.com/ATECorp/media/pdfs/data-sheets/Tektronix-TDS3000_Series_Manual.pdf)

Usually, when I measure the the voltage of the battery or even 5V itself on the oscilloscope, I use the Oscilloscope Tester Scope Clip Probe to attach the cathode and anode of the battery.

But the B200 ettus has only SMA and BNC connector, there is no way connect to the ground.

Does anyone know the way the measure the voltage of this device?

Thank you.

 

[Tom.G]

The shell of the connector, SMA or BNC, is Ground.

 

[rbelli1]

There is a BNC/TNC adaptor for scope probes. Sometimes it looks like a BNC/TNC connector with no locking ring and sometimes it is merely a cylinder that adapts the tip to the connector.

https://www.digikey.com/product-detail/en/cal-test-electronics/CT3655/CT3655-ND/5029183
The top silver item in this picture is a shabbier version of the above:
https://www.digikey.com/product-detail/en/teledyne-lecroy/PK001/PK001-ND/4941393

One designed specifically for you probe will work best but a brand mismatch will often work. As long as the clips in the adapter and the pin and barrel on your probe will fit together and make proper electrical contact it is fine.

I can't find a picture of the cylinder type one online. You will likely need one of the above as the newer probes usually don't have a pin large enough for the connector.

BoB

 

[berkeman]

The output of that RF generator board likely has a 50 Ohm output impedance. If you measure it with your 'scope probe, the mismatch in impedance will give you a 2x error in the output amplitude.

Also, you will not get the best bandwidth for this measurement with a 'scope probe. You should run coax from the generator board directly into your 'scope. Use a BNC-to-BNC cable and an SMA adapter to connect to the board, and use the 50 Ohm input impedance setting on the channel of your 'scope that you want to make the measurement on.

Also, it looks like the RF generator board can go a lot higher in frequency than your 'scope can measure, but you still should be able to characterize the lower frequency outputs of your board.