I made a DC measurement board based on ADC and ARM. Now I want to add 'self-calibration in filed' function to it. I think I need a voltage reference and a voltage divider. And I don't want to calibrate my calibrator. I just need the voltage output error from the setting value (calculated from reference voltage and divide ratio) don't exceed 0.1% (because the voltage reference I used only has a initial accuracy 0.05%, so I don't expect the whole system can achieve the same accuracy with it). Now I have two ideas:
- Use a resistor voltage divider network. If can't buy one, I need make it myself, using 0.1% metal film resistors. And I may need an analogue switch such as ADG seris, and precision OPs, etc.
- Use a MDAC. The DAC may expensive, but it may need less parts than the method 1.
Any suggesions? Which one is better?