Hi,

Is there any way to get rid of the ADC errors (offset, gain, etc ...) for the PIC16F887 micro-controller (I am referring to the built in ADC )?
How can the ADC for this device be calibrated to be as accurate as possible?

Thank you,

Buzai

 

You apply a known range of voltages to the input (using an accurate digital voltmeter to determine the voltage value) and then use that to generate a calibration table that is stored in the PIC to correct the voltage readings the PIC converter generates. You extrapolate between voltage levels to generate the correction factor for any particular input voltage.

 

Hi,

Isn't this method temperature dependent?
Are there any other methods?

Thank you,

Buzai.

 

That is going to be the basic idea for any calibration method. Sure, it will be somewhat temperature dependent but that inherent in the ADC itself. It should still be an improvement over the uncalibrated performance. And, you could add a discrete temperature sensor to do temperature compensation as well if you want to improve performance over a wider temperature range. If you really want more accuracy, you may need to consider an external I2C/SPI ADC.

 

Hi,

Is there any way to get rid of the ADC errors (offset, gain, etc ...) for the PIC16F887 micro-controller (I am referring to the built in ADC )?
How can the ADC for this device be calibrated to be as accurate as possible?

Thank you,

Buzai

Since you asked I guess you have some problems with your setup. Perhaps it is better to tell us what these problems are. All ADCs have some inherent noise problems. The output will always flicker some. Around 1 to two LSB

 

No problems . I am just interested in learning about the calibration of ADC modules from micro-controllers. I just picked the PIC16F887 randomly.

Thank you,

Buzai

 

The reference voltage is important here. If you rely on the Vcc, you won't even get 8 bits resolution.

One simple reference voltage source for instance is a 78l05 with voltage divider.

So the first step for better accuracy is to improve the voltage reference.

If you use switching regulators for supply you also may need an extra LC filter before the PIC.