Question : alternative current in to a pc

Hi Experts

is ther a way to measuer ac into a pc like a pc based  analoge to digital adapter as its for measuring electrical current or total disoled solids for a computer based water quality system I have already worked out ph and temperature via drdaq data logger

is there any usb ph I know there are smart ph usb adapters but they are $300 and I need temparature and they are expensive to the problem appears to get ec or tds I need to use 2 probes 1cm apart using ac as dc rips the molecules apart and gives a misleading reading

Answer : alternative current in to a pc

Another option will be the arduino boards, with them you can built a dedicated computer for your needs, how ever you'll need some programing and electronic skills.
http://arduino.cc/en/Tutorial/HomePage
http://www.maartenlamers.com/ThisIsWiring/

Other option
http://www.microcontrollerboard.com/
http://www.microcontrollerboard.com/analog-to-digital-converter.html