How to avoid fluctuating reading from load cell and strain gauge

[Shriharsh]

I want to plot stress vs strain curve. Area is given load is taken from load cell by this stress will be calculated, strain is measured by using strain gauges (half bridge configuration). I have made programme but the values taken from load cell and strain gauge keeps fluctuating. How to get stable and accurate value of load? If 5kg load is applies then it should show 5 kg only and not keep changing from 4-6 kg

DAQ 9237 is used and programmed Labview 2014 SP1

load cell data:

max load: 1.5ton(imperical)

rated output: 1.953mV/V

input resistance: 402+-10 ohm

output resistance:350+-5 ohm

[ben64]

You can do some averaging, most load cell displays are doing it. I usually average 10 to 100 measurements when measuring load cells.

What excitation voltage do you use? A higher voltage makes the output less sensitive to noise.

A sampling rate of 10k is pretty high for load cell strain gage measurements, you might also have a resonance issue. You can try different sampling rate. If your application allows it try keeping your sampling frequency below 1 Khz.

Ben64

[Shriharsh]

Thank you @ben64, lowering the sampling did work but still there are fluctuation.

I am new to labview software, can you tell me how to take average of those instantaneous 100 samples

[dr2]

Shriharsh,

You either need to get a different load cell or increase your load.  I'm not sure if you load cell is rated for 1500 kg or 3000 lbf, but either way you are using your load cell at much less that 1% of full scale and seeing fluctuations of less that ±0.1% of full scale.  Those numbers are completely reasonable for typical measurement equipment.

If you experiment is really only going to need 5 kg of load, get a load cell with a lower max load.  However, if you are simply verifying the functionality of your system and will eventually be applying much larger loads, don't worry about the fluctuations as they are relatively speaking very small.

-DR2

[Shriharsh]

My load cell is rated for 1500kg. My experiment need is 700-1200kg.

I did took readings for larger loads but it still keeps fluctuating, there is still small error. How can I minimize error? 

[Hooovahh]

You can also try to apply a low pass filter, and/or a dead band on your signal, but honestly a bad reading can't be resolved with software alone.  If the data coming in is flaky then there is little hope the software can fix it.  I'd also look into your setup first.

[billko]

Instead of trying compensate with software alone, the first thing you do is you want to clean up the signal physically before it gets to the measurement instruments.  This has the added value that maybe it will save your equipment from blowing up due to transients.  😉