External Analog Lowpass Filter (anti-aliasing filter) for NI-USB 6251

[johnsold]

Most likely you will need to place the filter between the AE coupler and the BNC2110. For a quick test you could use BNC cables with clips on the end to connect the filter components.  If that seems to work, then get a small box and wire the filter components to BNC jacks on that box.  If you use a plastic box like the coupler shown in one of your images, you need to wire the shells of the BNC connectors (grounds) together.  Metal boxes obviously provide better shielding, but if a plastic box is good enough for the AE coupler, plastic may be good enough for the filter.

Lynn

[pinguim]

Hi Lynn,

-Thank you a lot for these tips! I´ll try to implement them!

-The material of the coupler´s box I´m using is metal instead of plastic.

-If I need to place the filter between the AE coupler and the BNC 2110, so it would be necessary to recalculate the values of the external resistors (R3 and R4) which were proposed in your last solution. In this case, what values should be attributed to R3 and R4 if I set the channel´s switch to FS (Floating Source Signal)?. Please take a look on Fig.1, which is based on the manual of the BNC 2110.

-Considering the fact that my AE-sensor ist ground isolated and that it also occurs for the output analog signal of the coupler, so the source of the signal which is connected to the BNC2110 is actually a Ground-Referenced signal Source (GS). In this case, what values should be attributed to R3 and R4 if I set the channel´s switch to GS (Ground-Referenced signal Source). Please take a look on Fig.2, extracted from the manual of the BNC2110.

best regards!

[pinguim]

Hi Lynn,

-Thank you a lot for these tips! I´ll try to implement them!

-The material of the coupler´s box I´m using is metal instead of plastic.

-If I need to place the filter between the AE coupler and the BNC 2110, so it would be necessary to recalculate the values of the external resistors (R3 and R4) which were proposed in your last solution. In this case, what values should be attributed to R3 and R4 if I set the channel´s switch to FS (Floating Source Signal)?. Please take a look on Fig.1, which is based on the manual of the BNC 2110.

-Considering the fact that my AE-sensor ist ground isolated and that it also occurs for the output analog signal of the coupler, so the source of the signal which is connected to the BNC2110 is actually a Ground-Referenced signal Source (GS). In this case, what values should be attributed to R3 and R4 if I set the channel´s switch to GS (Ground-Referenced signal Source). Please take a look on Fig.2, extracted from the manual of the BNC2110.

best regards!

[johnsold]

If your signal is ground referenced, then you only have one half of the filter. Since the filter had the center grounded, each half was independent with respect to ground.

I think you can just use R3 and forget R4.

Lynn

[johnsold]

I think you can just use R3. The differential signal filter is symmetric with respect to ground so you only need half of it for a ground referenced signal.

Lynn

[pinguim]

Hi Lynn,

-Thank you for the tips regarding the external resistors. I´ll try to implement them and let you know if it works.

best regards!