Inconsistent measurements for 12, 14 and 16bit sampling
2483 Views - Created 13/12/2016
Which language version of the ADC library are you using for your project? I will check the library to make sure there are no bugs when converting at the lower bit rates.
One possible cause for instability when sampling the ADC is if the power supply for the Raspberry Pi is unstable. The MCP3424 ADC chips on the ADC Pi Plus have an internal voltage reference and smoothing capacitors but any major voltage drops in the power supply will cause the voltage reference to become unstable which will in turn show up as fluctuations on the sample readings.
If the power supply is unstable then one solution would be to use a second lower current power supply to power the ADC Pi Plus directly. You can do this by connecting the second power supply to the 5V and GND pins on the ADC Pi Plus and cutting the 5V trace on the PCB as shown by the red line on the photo below so it is disconnected from the 5V pin on the GPIO header. This should eliminate any voltage drops or spikes on the Raspberry Pi power supply from affecting the ADC sampling.
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