Excessive Noise SCXI-1520

[eroberts@water.ca.gov]

I have (4) SCXI-1520 modules, used to measure bridge type sensors.  While tesing them with a Fluke 753 Process calibrator, the two older modules 186338D-01 exhibit high noise (AC 60Hz).  The injected signal is 100 mVdc and the Fluke 753 is on battery power.  The AC noise is 4 mVac non-sinusoidal.  The other two SCXI-1520 modules are noise free using the same chassis and setup.

[BriBear]

Hi eroberts@water.ca.gov,

Could you tell us more about your hardware configuration? Such as:

• What SCXI chassis do you have?
• What cables are you using to make these connections?
• What environment is this in?
• What slots are the two older modules in?
• Is the noise on all channels of the two modules?

[eroberts@water.ca.gov]

Hi Briana,

We have (2) SCXI-1000 chassis, (2) SCXI-1314 connector blocks.  The connector blocks have 3 feet of Belden 8723 signal cables installed on each channel.  The cables are terminated with MIL-C connectors.

The modules that fail exhibit noise on all channels. They have been swapped into various chassis and terminal blocks and fail in any position.

[BriBear]

Thanks for the information. You mentioned that the two older modules were the ones experiencing noise. When is the last time the modules were calibrated?