I'm interfacing a load cell using a HX711 ADC to read its results into a microcontroller.
Many of the code samples take numerous readings (about 10) and average the result, but I was wondering if the readings could be improved by simply adding a capacitor across the load cell's sense leads to form a low-pass filter? Then I could take a single sample and use less energy.
Is this a worthwhile endeavour? Would a ceramic capacitor be too small, or would a bipolar electrolytic have too much leakage and affect the results?
Best Answer
Adding a capacitor across the sense lines can help reduce noise and smooth the signal. Note that in the HX711 spec sheet (page 6) there is even a reference schematic/PCB that shows an RC network on the sense lines, it includes a 0.1uf directly across the sense pin inputs.
If used the capacitor should be a non-polarized low leakage type (for e.g. Poly type), as any leakage across this capacitor could cause some amount of error. A high quality ceramic type may work well if you don't really need the highest performance. A higher value capacitor could help but at a certain point your response time to load changes will suffer. https://cdn.sparkfun.com/datasheets/Sensors/ForceFlex/hx711_english.pdf
It would still be a good idea to do some averaging of multiple conversions as there can also be noise coming from the rest of the system.