Load cell Reading in newton...making a newton meter with a load cell..!!

Hellooo… i’ve been working on a project at some point i have to make a digital newton meter to measure static friction of a sliding mechanism…this sliding mechanism require between 0.2N to 0.8N of Static friction in order to function…i have chosen a 1Kg loadcell to sense the friction force… since the loadcell reading gives in Kilograms, i have added this part to the coding …

scale_read_kg =scale.get_units();
lcd.print(scale_read_kg*NEWTON_CONSTANT, 2);

but, i came across a mechanical newton meter (it’s not digital and i can’t have it forever) that can read around 0 - 1 N… then i compared it with my load cell reading and this is what i got,
:
mechanical reading - 0.1N : 0.2N : 0.3N : 0.4N : 0.5N

Load cell reading - 0.15N : 0.41N : 0.52N : 0.58N : 0.61N

where do you think went wrong?

What is the value of NEWTON_CONSTANT? 1 kilogram force (kgf) = 9.80665 Newtons (N). Did you carefully calibrate your scale to read 0 with 0 force and 1.000 with 1 kg force?
0.5N = only 0.050985811 kgf, you may need a smaller capacity load cell.

I could imagine a difference between static and dynamic force measurement. Which readings do you get if you put a static weight on your load cell? That’s the best and most reliable calibration method. Then record minimum and maximum force in friction measurement for assumed constant friction, to find out how reliable your measuring arrangement is.

Hi;
How did you compare the two meters?
By hanging known masses from them, or by trying to measure static friction?

Tom..... :slight_smile:

This looks like maybe you are using an HX711 library...

scale.get_units()

In that library, units can be anything you want. If you want to calibrate your scale in Newtons then go ahead. You don't need to add any conversion factors later.

Place a force of 9.8N (1kg) on the scale. Read off the scaled number and adjust the scale that your code passes to the library until it reads 9.8.