Boost a 0-10mV input signal to Microcontroller (STM32) ADC

Question

Hello,

I have a Load cell which generates an output of 0-10 mV. I have to read this output of the Load Cell into my micro-controller (using the in-built ADC peripheral). My controller is a STM32F4 family controller which works off a 3.3 V supply.

I have researched possible options of:

Using an Op-Amp, adjust gain and feed output to Controller ADC.
Use an Instrumentation Amplifier, adjust gain and feed output to Controller ADC.
Use an external ADC which works in the 0-10 mV range and feed output to Controller ADC.

I am more Firmware developer and not very familiar with which technique would work and which won't. Any suggestions? If none of the above, do let me know which area to research so that I can delve into that as well.

dougw · Answer

You could check my blogs about a solution I designed to handle a compression load cell to see if it works for you: Sixth Sense - Sensor Circuits - GraffitiBot blog 3 Sixth Sense - Load Cell PCB - GraffitiBot blog 8

michaelkellett · Answer

Lots of additional questions need answers before I can give more than a very general response. Like: Will the load cell output always be positive - load cells have offsets so the output with zero load is never quite zero. You will need biasing of some kind to put the zero where you want it in the 0 - 3.3V range of the micro's ADC. Will you have long wires between the board and the load cell - if so then you'll need RF blocking filters. The 12 bit ADC probably does not justify using a 6 wire load cell connection. What frequency range do you need. Most of my load cell work has used better ADCs - I've found it necessary to use a chopper amp - the Microchip MCP6V61 or MCP6V64 are cheap and pretty good. I've used them in weighing applications with 24 bit ADCs and been pleased. What's the final application ? (I'm away for the next few days so I won't respond any more until Monday). MK

rsc · Answer

I would suggest a two-stage amplifier using low-noise differential pair inputs and shielded twisted pair cables from the load cell.

You can easily get a few mV of electrical noise in a room just from light fixtures. Power from a battery will also reduce noise.

Scott

Boost a 0-10mV input signal to Microcontroller (STM32) ADC

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