The field of radiocarbon dating has become a technical one far removed from the naive simplicity which characterized its initial introduction by Libby in the late 1940's.
It is, therefore, not surprising that many misconceptions about what radiocarbon can or cannot do and what it has or has not shown are prevalent among creationists and evolutionists - lay people as well as scientists not directly involved in this field.
It is confusing when the maximum date for Carbon 14 is listed as 60,000 years and 80,000 years in the same article (Chapter 4 Dating Methods by Roger Patterson and the reference article summary 4.2 by Riddle.) and as 50,000 years in another (The Answers Book) as well as 95,000 years in the Creation College lecture by Dr. This is why there is the disparity in the quoted limits to radiocarbon dating, as highlighted by this inquirer.
This is due to the fact that the AMS instrument has to be calibrated, and yet the organic materials used for calibration (that are supposed to be so old they shouldn't have any detectable radiocarbon left in them) all contain so much radiocarbon that it means samples of unknown age can't yield dates above this radiocarbon barrier.
Accelerator mass spectrometry measures the amount of carbon-14, or radiocarbon, present in a sample, which can be used to calculate its age.
But the radiocarbon detected in diamonds is equivalent to ages of up to 80,000 years.
So you can see why the various age limits have appeared in different publications of ours.
Direct AMS operates two different AMS instruments, an NEC Pelletron 500 k V and an Ion Plus MICADAS 250 k V.
The differences in design for these two instruments is significant, but the general principle in achieving analysis is the same.