I remember when my friend used to work off the Ivory Coast of Africa, he had to provide certification EVERY time he went out for a 120 day cycle. What he would do is purchase a brand new meter and take it with him out there to use. Then he would sell it before he came back to the states to one of the technicians over there for about 2x what he paid for it! He said it was much better to do that than to get his own personal stuff re-calibrated every time he went out.