how can i build a simple ph meter?

hello guys,this is badhan from bangladesh.i am a student of Industrial and production engineering.In my running semester i have a course in which i have to modify a device which gives a digital reading.I try to make a simple digital ph meter.

so,i want to know the process of converting the analog reading to digital reading.And thats the motto of this lab sessional.

so,plz help me to describe the converting process and the work principle of a simpliest digital ph meter.

Try pH meter - Wikipedia, the free encyclopedia

So a simple meter is a pH (e.g. glass bulb) sensor with an amplifier to increase and offset the sensor measurement feeding into a voltmeter.

actually, read a bit further down the wiki page; there's a link to building the simplest pH meter.

If you want to know how an analog signal can be converted to digital signal you can look at: Analog-to-digital converter - Wikipedia, the free encyclopedia . There are lots of info about it right there and in the web, just ask Google