Measuring Floating Sources with USB-6225 and BNC-2090A + BNC-2115

[jarjarvai]

Greetings,

I'm using the BNC-2090A and BNC-2115 with a USB-6225 DAQ to log the outputs of 32 (8 + 24) current sense transformers. The BNC-2090A and BNC-2115 seem to have some differences in the input signal conditioning options, on the BNC-2115 in "FS" mode there is a 5kOhm resistor connected to ground in parallel with a 0.1uF capacitor, as referenced in the manual : 

However when measuring Floating Sources in Differential mode on the BNC-2090A, it is suggested to have 10-100kOhm resistors so as to provide a return path for PGIA bias currents. I'd like both the BNC boxes to have identical input signal conditioning, in that case would it be advisable to install 5kOhm in R31 (B) and 0.1uF in R50 (G) positions shown below?

[JiwhanS]

Hi Jarjarvai,

Chapter 3 Signal Conditioning in the BNC-2090A Manual should have all the steps to guide you to create identical signal conditioning. Check out the section Building Lowpass Filters.

BNC-2090A User Manual - National Instruments

http://www.ni.com/pdf/manuals/372101a.pdf

[jarjarvai]

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@JiwhanS wrote:

Hi Jarjarvai,

Chapter 3 Signal Conditioning in the BNC-2090A Manual should have all the steps to guide you to create identical signal conditioning. Check out the section Building Lowpass Filters.

BNC-2090A User Manual - National Instruments

http://www.ni.com/pdf/manuals/372101a.pdf

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Hi Jiwhan, thanks for the reply! However, I’m not looking to build an LPF since the ‘FS’ mode on a BNC-2115 would have 5kOhm/0.1uF in parallel, connected to AI GND. Please refer the diagrams from my first post.

Thanks,