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Tool/software:
Hi, I have an embedded system that reads a load cell using an atmega microprocessor. the first version was an atmega 328pb, and was using HX711 load cell ADC. This worked very well, resolution was very good and very stable. This was even though the system includes a pump. The new version changed to atmega 2560, and load cell is read using ADS122C04. This is a lot less stable, both when the pump is off, and much more when the pump is on. Both are 24 bits, so i was expecting similar results. I'm using 128 gain, and the input is set to ain0-ain1, internal ref. attaching an image of my schematic.
any help would be much appreciated.
thanks
Hi Eitan Pollack,
Connecting a resistive bridge (such as a load cell) to an ADC typically requires implementing a ratiometric measurement.
This requires using the voltage across the bridge as the voltage reference for the ADC, rather than using the ADC's internal reference. This should provide much more stable measurements.
Figure 3-1 illustrates how bridge measurements are typically made with a ratiometric reference configuration.
The output of the bridge is measured by the ADC while a single source is used as both the bridge excitation
voltage and the ADC reference voltage.
More detailed information on this topic can be found in the following app note: A Basic Guide to Bridge Measurements (Rev. A)
Is the load cell being measured 4-wire or 6-wire?
What is the excitation source for the load cell/bridge? Is Voltage or Current Excitation being used? Is it the same 5VDC used for AVDD and DVDD?
Best Regards,
Angel
