50 Hz noise from SG03

[RobertJensen]

Hi

I am using a SG03 strain gauge module with the SCC-2345 to measure various kinds of strain. The module behaves very well and I am quite happy with the sensitivity. However, one really significant problem is present, namely noise from the net-frequency (50 Hz). The noise is as large as 12 \mu-strain and this means than I really need to average over one complete cycle to make any sensible measurements thus limiting my effective bandwidth considerably. Is this problem avoidable in any way or could my module be defective?

I have analyzed the 2.5V excitation voltage and this does not show any kind of noise and thus the noise must originate from the measurement itself.

Best regards
Robert Jensen

[Henrik_Volkers]

Line noise depends a lot on how your wire (in hardware not in LV ) your sensor to the SCC.

Mostly it's due to a groundloop.

There should be at least one KB- article about grounging, ground-loops, line noise...

Please provide a detailed description on how you wired your system.  Some keywords: shielded cable, shield only connected on one side, bridge conduted connected to DUT??, DUT grounded? differential input?

more exotic : 50Hz vibration on DUT?  

[RobertJensen]

I am aware of the risk of groundloops even though I cannot rule out that this is the case here. However, in terms of wiring the SG03 does not leave much choice. I have two wires for the excitation current (and I have measured that these are indeed noise-free) as well as a single wire from the strain-gauges into the SC2345. The other half of the bridge is terminated inside the SG03 leaving few options for wiring.
Noise from the DUT is not an option, this is just a single metal rod with strain gauges mounted on opposite sides of the rod. I believe the LabView term for this configuration is Half Bridge II. The dut is not electrically connected to anything.

Best regards
Robert

[Morini]

Hi Robert,

Please take a look at this KB-link. It should be applicable for SG03 module as well.

http://digital.ni.com/public.nsf/allkb/5D9D06457CB4DD9786256B0B00568EDC?OpenDocument

Thanks!