Sensitivity of SC2345 and Strain gage modules SG02 and SG03 (So sensitive that handling of conditioner while causes significant noise)

[wilvil2000]

I recently purchased a SC-2345 with two 350 ohm strain gage modules, SG02 (1/4 bridge), and SG03 (1/2 bridge). Upon developing a small data logger for these I encountered a strange situation which boggled my mind. I noticed that the slightest bump against this conditioner would excite the modules and produced noise levels unacceptable to my purposes. My opinion is that this instrument should handle slight vibrations and it appears as if it can’t.
My question to any owner of this equipment is; Do you get the same results if you tap on the cover of the SC-2345 as I do?
I’ve included some screenshots of readings I’ve taken during my investigation. Please let me know what you think.

[e-Cash-Money]

Hello wilvil2000,

The SCC-SG modules are not really tested for vibration, so we can't really on any testing or specifications to give us an answer.  The issue might be caused by the two half bridge completion resistors that are socket-mounted in the module.  You could try soldering the resistors down to improve the results, but remember, modifying the hardware voids the warranty, so try this at your own risk!!!

[wilvil2000]

Dear E.Lee,

Of course, I could probably solder everything I think is loose and perhaps come up with a fix (maybe?). That is assuming that the problem originates in the strain modules. I wonder if other non-strain modules behave the same? It's too late already for I've already returned the product back to NI. But my problem is quality. I would expect this product to handle better than they do. The way I see it is that if I was to ever record strain on a moving train, bus or car, using a laptop, that I wouldn't be able to use this device due to the problem mentioned above.
What I would like to get from this conversation is that National Instruments is working on the solution to this, that's all. I believe this could be a good product and I'd like to be able to buy this device in the future once the opportunity arrises, but it needs to be a slight more rugged.

wilvil2000

BTW - I've attached the screenshots I said I would on the first message.

[Logan_K]

R&D has been looking into this issue for several days now, and there are aspects of the noise from the vibrations that we are still attempting to understand. I have confirmed that the noise is not associated with the socketed quarter bridge resistors or the offset nulling circuitry. No noise is present when the inputs are shorted together, or when I use a different sensor-type, like a load cell. This confirms that the noise is being introduced at the input of the modules, and appears to be dependent on the type of transducer that I use. I am not sure yet if the noise is associated with the excitation circuitry, but I have confirmed that the excitation circuitry does not exhibit any noise at all, so I think that is unlikely. I will update this post with our findings as we investigate this noise further.

Logan K
NI SIgnal Conditioning R&D