Mathematical formula that converts voltage to weight the HX711 is using

[ivanedpratama]

Hello guys, im currently working on a load cell project using strain gauges and the HX711 amplifier.

Coding wise all good but ive been searching and reading everywhere but still could not find how the HX711 converts voltage coming from the load cell into weight? is there a formula that converts voltage to weight ? if so whatt is this mathematical formula that the HX711 is using?
I tried to see if maybe the arduino does the conversion of the voltage to weight but still no clue.
It would be a great help if u could point me to the right article or the formula in question because i want to understand the principle behind going from voltage to weight and if you would be kind to explain if the microcontroller does the conversion to weight and the hx711 just amplifies the signal or not.



I use a 5 kg loadcell and a NodeMCU ESP8266 microcontroller with a load cell input voltage of 3.3 V



Loadcell Specifications:
Rated Load: 5Kg
Rated Output: 1.0mV/V±0.15mV/V
Zero Output: ±0.1mV/V
Creep: 0.03%F.S./30min
Input End: Red+(power), Black-(power)
Output End: Blue/Green+(signal), White-(signal)
Recommended operating voltage: 3 ~ 12 VDC
Maximum operating voltage: 15 VDC
Input Impedance: 1115±10%?
Output Impedance: 1000±10%?
Protection class: IP65

Thank you ...

 

[ivanedpratama]

I use a weight of 500 grams that has been weighed with a scale. then I gave a voltage of 3.3 V from the psu to the E-/+ cable (load cell) and the A-/+ cable was connected to the avo meter
so I get that value.

 

[KlausST]

Hi,

A photo tells so much more. It shows the reality.

Text and sketches are influenced by your knowledge (that we don't have), your expectations .....

We still don't know what measurement device you use, which measurement tool setup, cable length.
You know what power supply you used, whether it is fixed or adjustable, how precise it is and how much noise you can expect.
You know whether you really did a measurement at the wires of the sensor, or you did a measurement of the supply without the sensor connected, or you just expect it to be 3.3V.
We don't know this.

Mesuring millivolts is simple as long as you know what you do. People here in the forum have quite a huge range of experience. From absolute beginner to absolute expert.
I guess ( and that's all I can do) that you know that there is a huge difference doing a true RMS measurement (including all noise and mains hum) versus duing the same measurement but in "average mode" (exluding most of the noise).

And so on. One could write a book about correct and accurate strain gauge measurements and the pitfalls.

Klaus