MAX1496 is an ADC with internal 31/2 digit LED display driver. This is an ideal IC for simple voltmeters. You just need the IC, and a couple more components and you are done. The following is a circuit I made using EAGLE. This is kind of a knock off circuit I built after going through the datasheet.
Voltmeter using MAX1496
All the controls are connected to a 10pin FRC which is to be hooked to a microcontroller to automatically set the ranges. RJ1 and RJ2 controls the LED drive currents. They are made as female pin headers to insert resistors. More details will be added soon…
Datasheet : MAX1496, MAX1447, MAX1498 datasheet