How to configure resistor network on BNC-2095 with SCXI-1100

[TomBriggs]

The manuals are not entirely clear on this point. I have a BNC-2095 that is connected to a SCXI-1100, and will be reading voltage input signals from pressure transducers and other assorted sensors. The manual indicates that I should not use a ground-referenced input with the BNC-2095 and have the 10-ohm resistor networks in place, but it only discusses installing the 10-megaohm resistors for use with the SCXI-1102. What is the correct configuration for use with the SCXI-1100?

Thanks,

Tom

[RT4CY]

Hi Tom,

Using the 10 MOhm resistor network instead of the default 10 Ohm resistor network with the SCXI-1102 allows you to measure both floating and ground-referenced signals.  According to page 7, Table 2 of the SCXI-1303 manual, this is not recommended with the SCXI-1100.  I will verify with R&D that this is also the case when using the SCXI-1100 with the BNC-2095.

If you are certain that your signal is ground-referenced then you should remove the default 10 Ohm resistor network.  The input impedance should be high enough to prevent any sort of ground loop.  Check page 5, Table 1 of the BNC-2095 manual for the appropriate jumper settings when measuring ground-referenced signals

IMPORTANT NOTE:  Do not attempt to measure a ground-referenced signal with the default 10 Ohm resistor network installed.  This is well documented in both the BNC-2095 and the SCXI-1303 manuals that it may cause damage to your hardware.

[kenkar]

Hi Ron,

Did you manage to get an answer from the R&D? I also agree with Tom that the manual of the BNC-2095 is not entirely clear. I have a mixture of floating and grounded signals to connect to the BNC-2095.  What is the best way to configure the BNC-2095?  You mentioned "if you are certain that your signal is ground-referenced then you should remove the default 10 Ohm resistor network." I cannot figure out why it is necessary to remove the 10 Ohm resistor network. By keeping the ground referencing switch open, would it not make the Ch- of a grounded signal disconnected from the resistor network? I believe the ground referencing switch is the one described in Table 1. Please correct me if I am mistaken.

Regards,

Kenneth

[RT4CY]

Hi Kenneth,

Sorry for not getting back to you sooner, I was out of the office.  You are correct that keeping the ground referencing switch open would disconnect the grounded signal from the resistor network.  However, the warning in the manual does caution against connecting a ground-reference signal with the resistor network in place on page 6. 

You also asked about how to connect a mixture of floating and grounded signals.  Take a look at page 2-7 of the SCXI-1100 manual.  Leave Jumper W1 in its default setting (parking position), and connect your floating channels to the chassis ground on the terminal block via wire.

Let me know if you have any other questions.