Voltmeter

Overview

Here is a simple project with PIC 12F675. This voltmeter will work from 0V up to 50V (the resolution is set to 0,05V). This voltmeter use PIC12F675 with A/D converter (resolution of A/D conversion is 10 bit). I don't think you need better performance than that for simple measurement.

Voltmeter - feature list

• range: 0-50 V
• input impedance >10 M ohm
• resolution 0,05 V in entire range
• powered by 9V batery ( 8 mA/9V )
• very small dimensions: 33 x 42 mm

Imput part

The PIC's analog inputs accept voltages from 0V to +5 V.Therefore a TLC271 with a voltage divider is placed before PIC to increase the input resistance and range of the voltmeter. 

Voltmeter schematic

A  LM336 is used as a reference voltage source. This is a precision 2.5-V shunt regulator diodes with low-temperature-coefficient.It is put in a T092-package and you may replace it by another one. The LM336 - series is useful as precision 2.5-V low-voltage references for digital voltmeters, power supplies, or operational-amplifier circuitry. The 2.5V voltage reference makes it convenient to obtain a stable reference from 5V supplies.