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Questions &/or issues related to products in the Qwiic category should be posted in this forum. To learn more about Qwiic, consider checking out our pillar page on the Qwiic system.
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By simobv
#209396
Dear Sparkfun support, dear community
I am rather now to prototyping and electronics in general, so sorry if the questions I am going to ask you will be excessively naif!
I recently bought a Qwiic Scale NAU7802 that I connected to my Arduino Uno via the Qwiic Shield. I would like to use this board to read an absolute 4 wires pressure sensor from Kulite (XTL-123B-190M). This sensor is calibrate, so I know the relationship between Volts and Bars. Now, I just would like to use the Qwiic Scale to get the output signal and to amplify it, since the output voltage is of few mV only.
What I need to do in order to read my pressure, is to get the calibration factors that can lead me from the raw reading to a voltage, so basically the a and b parameters of the following equation: V = a*(x-b), where x is the raw signal.
The first thing I thought to do is to measure b. I then simply plugged the Qwiic scale without plugging any of the sensor wires and used the Exemple 1 of the library. I do get a reading, but the problem is that every time I close the serial monitor and I open it again, I get a different reading! I monitor the signal over several seconds and it is quite constant: it changes suddenly every time I restart the serial monitor/plotter. I also tried to get the signal via the serial library in Python 3.8 and it behaves the same.
What am I missing?
Thank you in advance for every help you may provide.

Best
Simone