Rancang bangun sistem kontrol sample changer berbasis PC pada perangkat radioimmmunoassay (RIA) nucleus model 1600 gamma counting menggunakan modul antar muka USB devasys 12C 1/0 = Design and development of sample changer control system with PC base on radioimmunoassay (RIA) peripheral nucleus model 1600 gamma counting using USB interface devasys I2C I/O module