weight scales offset

[cora38]

Hello,

We recently bought 2 weight scales from Adam equipment, model number "HCB 602H". We pluged  them to a computer using RS 232 communication port.

We want to measure continuously a fluid flow into a container with a sampling frequency of 30 seconds. We developed a Labview program to acquire the data (under Labview 2010). We used the examples provided with the drivers (NI VISA 4.6) called Adam Equipment Highland Series Acquire Measurement.vi.

The program works well. We need to measure the fluid flow during several weeks.

After few days of measurement, we  observed an offset in the weight... After several tries, we realized this offset comes after about a day of measurement and we think it might be the temperature changes that affects the weight scales measurement. We do not know how to solve this problem.

Could you help us? Do you have any suggestion?

Regards,

Coralie Aubert

[Henrik_Volkers]

If not explicitly stated in the datasheet I would assume normal temperature drift and even sensor creeping. ... usually no problem because before a measurement you do a tara / zero / autocalibration ...   weigth scales are rarely made for longterm measurements....  What has the manufactor answered to your question? 

In your case :   can you lift the container and do a tara/ zero inbetween (every 1-2 h) ?   (max range is 600g...   hire a school kid to build a lego MC that lift the container and press the tara button 😉 )

[cora38]

Hi Henrik,

Sorry for the late reply but we've tried many things to solve this problem.

Our measured drops are very small and the manufactor advised us to modify some parameters to remove some filters which could filtered those measurements... We still observed the same problem with this new configuration of the scale and we think sometimes the drops are so small (under the scale resolution) that the scale does not take it into account...

Thanks for your help,

Regards,

Coralie

[Henrik_Volkers]

if you just need a value every 30s and you have a sort of container on the scale , it:s enougth time to mechanical lift the scale, make a tara/zero and place the container back on the scale to do a measurement.