Patent ID: 8741655

Claim:
A method of determining a position of one or more test sample cards carried by a carrier as said carrier is moved through a sample testing machine, said carrier having a plurality of test sample card holding features, the method comprising the steps of: providing a loading station where the carrier is loaded into the sample testing machine; providing a plurality of processing stations for processing the one or more test sample cards; providing a drive subsystem for moving said carrier through said sample testing machine in a predetermined longitudinal path; providing a plurality of position tracking features in said carrier, said position tracking features formed in said carrier in alignment with said test sample card holding features in said carrier, wherein said position tracking features comprise void features in said carrier; moving said carrier through said sample testing machine; providing a plurality of optical interrupt sensors at fixed positions along said longitudinal path in said sample testing machine and in proximity to said plurality of processing stations; providing a computer processing system in communication with said plurality of optical interrupt sensors for receiving processing signals sent by said plurality of optical interrupt sensors; detecting the position tracking features with said optical interrupt sensors and said computer processing system, thereby detecting the position of at least one of the test sample cards.