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 ...

[santo_13]

This does not seem to be related to the NI discussion forum. Please refrain from posting unrelated questions.

Now, to answer your question,

There is no defined conversion factor as the HX711 does not know about the load cell you've connected externally.

What you do is called a linear fit calibration,

1. Do not apply any load (X1 = 0Kg), now make a measurement, note down the ADC value from HX711 as Y1
2. Apply a known load, say 1Kg (X2 = 1Kg), make a measurement, and note down the ADC value from HX711 as Y2
3. Calculate the calibration factor, m = (X2-X1) / (Y2-Y1) : this gives you Kg per ADC code
4. Since Y1 corresponds to no-load, this becomes offset c

To make a calibrated measurement, obtain the ADC value, and convert this ADC value into equivalent 

Weight in Kg = (ADC value * m) - C

[ivanedpratama]

thanks for the response.

I still have questions. how to calculate the hx711 module on the gain used on channel A.