NI myDAQ strain gauges data acquisition

[lorenzo26]

Hi everybody,

I am acquiring data from two strain gauges placed in Half Bridge configuration on the two opposite sides of an alluminium beam clamped on the table. 

I am using a NI cDAQ 9174 and a NI 9218 module with a NI 9986 connector and data are acquired in Signal Express.

In the  "strain_config" picture you can see the Strain acquisition configuration. I have performed a strain calibration and everything seems to be all right.

My question is: why there are some oscillations and peaks (at 50 Hz + k*50 Hz) in my acquisition when the beam is perfectly still (figure "strain01")?

I thought that it is due to the illumination (50 Hz) of the room but it is not.

In figure "strain02_1peak" you can find a screenshot of the signal when the beam is vibrating (the first peak appears).

If you have any suggestion I would be grateful.

Thank you very much,

Lorenzo

[Lamber_86 · Accepted solution]

Hi lorenzo,

seems that there is a classic 50Hz noise, that can be originated bey different sources (Power line, external noise etc.). I suggest you to reduce the sensor distance as much as possible and if the disturb persist, you'll should use a sw filter (stop band at 50Hz).

[lorenzo26]

Thank you Lamber.

Do you mean to reduce the length of the cables from the sensor to the NI 9986 connector?

[Lamber_86]

yes, it could be a solution