Hello All,

We have a strain gauge that is bonded onto the drivetrain shaft for torque measurement. The Strain Gauge (SG) signal is then transmitted to receiver wireless. Later we have an IPEtronik (which is basically like a DAQ system) that gather all the signals from the CAN Bus and SG to be collected at one place and then sent to laptop for acquisition. I have attached the power and data flow for your reference.



I have attached the snippet of the noise from the SG data. Not sure where it is coming from it doesn't look periodic. The FFT on that gives me dominant frequencies around 2 to 6 Hz. Note: I am sampling data at 50 Hz there is possibility of aliasing.



This is a snippet of how rear of my Strain Gauge Receiver is connected. I am planning to shield the voltage output wires since it is close proximity to the power input.



Let me know if you guys have any suggestion or potential noise sources.

Thanks,

 

Was there any noise from the strain gage amplifier?? Is it possible to power the system from a 12 volt battery to see if the problem is power supply related? Is it possible that the noise is related to the shaft, either electrically or mechanically?? Inverters and switcher power supplies can produce noise, but usually at a higher frequency.

 

If you isolate the strain gauge from the shaft, do you get the same noise?

 

Thanks guys for your advice. This was test was conducted on a site. The results I am showing you is after post processing. I am currently seeing a way if I can replicate this in my laboratory.

I do remember a while ago I used a Strain Gauge Bridge simulator that can mimic the strain gauge operation. I did not see any noise when I did that in my lab.

I also checked all the power sources signals mostly they are clean.

@joeyd999 and @MisterBill2 I don't have opportunity to isolate SG now. But I found another piece of information, I saw this noise also when the semi-truck was not in motion. Basically the engine was started and it was idling (transmission was not engaged). I have attached the image below.



Like Misterbill2 mentioned may be amplifier is amplifying noise mechanical noise that is coming from engine. I have attached another image of how everything was mounted on the shaft FYI.

 

One simple thing would be to rev the engine a bit and see if the rate of those pulses increased. It could be mechanical noise or even electrical noise. It looks a bit like ignition noise spikes. But that is just a guess. It could actually be mechanical noise, even.

 

Connect the strain gauge input to a set of resistors that match the bridge, then observe.
The whole show is subject to vibration, you need to determine if it's clean or not without the bridge.