I have been asked to look into purchasing a thickness tester for our site. I know very little about the technology & was hoping someone could point me to some info to help me understand it & make an informed proposal.

http://www.inxs-inc.com/cgi-bin/menu.cgi?a=view_prod&id=12556

The Above link is for a instrument we have had tremendous success with. We have had a Krautkramer Branson DME tester in use for predictive use for over 15 years. I can't attest to the above links' credibility but the instrument is outstanding

Here is a link to a variety of Ultrasonic Thickness gauges. Which one is best suited will depend upon material to be tested, required thickness, if you want to measure through paint, or if you want to measure coating thickness, etc. Feel free to contact via e-mail if you would like to discuss:
http://www.reliabilitydirect.com/ultrasoundproducts/thicknessindex.htm

What are you going to be testing? We went through the same process a few years ago and the person designated to do this had to go through some extensive training and API 510 Certification since we were looking at Pressure Vessels.

Mick3040 has a good point. Depending on what you are being asked to do certification could be necessary. The instruments I have been around are Krautkramer Branson and Panametrics. The documentation program we use was a form of autocad. That was for drawing the pipe and vessels and marking the measurement locations with thickness. This is a very extensive non-destructive program when you get in to it.