Accounting for signal drift

[Zac58]

Hello,

I'm a beginner LabVIEW-user and have a question that maybe painfully obvious to a more experienced user.

I am using a CP225D Sartorius analytical balance to record changing mass at the mg-scale due to withdrawal and dispensation of a fluid in a container. Regardless of blocking room airflow, approximate room temperature, and unchanging or repositioning the initial load for several hours, a fairly linear and continual negative drift will occur for the balance readout. This drift occurs regardless if there is anything on the scale or not. I am using supplied Sartorius VI's to read and record the readouts.

How can I use LabVIEW to adjust this signal for this negative drift using the linear relationship I can derive from previous sample runs? I have previously tried to collect the signal from the difference between the balance readout and the linear relationship I have approximated, but as time progresses, even this manipulated signal drops to the exact balance readout if it had allowed to run without being manipulated. Better still, how could I manipulate the signal from a prior flat sequence frame curve fitting to the signal being recorded in the next frame?

I would appreciate any direction or help that could lead me to a solution. I tried contacting Sartorius helpline but little help was offered. I will share as much information as I can.

Thank you for reading this,

Zach

[johnsold · Accepted solution]

Zach,

The instrument probably does not drift linearly forever or the value would eventually go out of range.  The manual I donwloaded requires 30 miniute, 4 hours, or 24 hours of warmup time, depending on the model and the application.

Can you try to record the readings once per minute for 24 hours starting with a cold intstrument and letting it run in as stable an environment as you have available? Record the ambient temperature also, if possible.  Does the drift ever stabilize?

How large is the drift compared to the signal you need to measure? How fast is the drift? How fast does your fluid dispensing change the readings?

Lynn