How to make a simple voltage measurement device

[houkensjtu]

Hi there!
I want to make a simple voltage measurement device myself which can:
1. Measure a DC voltage range from 100-200V
2. Have reasonable accuracy, say error less than 0.1%

I thought a cheap multimeter may give me some idea so I tore down my multimeter, I expected that there would be an AD converter like chip, but the only thing I found is a single central chip(most likely a microcontroller) on the board.(you can find my photos in the attachment)

Here is my question:

1. What is the standard way to measure voltage in digital multimeter?
2. How should I deal with the high DC voltage (because usually microcontroller can't afford that high voltage input)
3. Is it better to use a seperate AD converter than using microcontroller's build-in AD converter?

Thank you all!

[Richard Crowley]

1. What is the standard way to measure voltage in digital multimeter?

Most lower-end DMMs have specialty chip like Intersil ICL7106. It handles everything from measurement to display-driving.

2. How should I deal with the high DC voltage (because usually microcontroller can't afford that high voltage input)

Simple voltage divider. Add protection clamps (diodes, etc.) if there is danger of over-voltage.

3. Is it better to use a seperate AD converter than using microcontroller's build-in AD converter?

Does the microcontroller's built-in AD converter meet your requirements?