We designed and developed a desktop ac susceptometer for the characterization of materials. The system consists of a lock-in amplifier, an ac function generator, a couple of coils, a sample holder, a computer system with a designed software in freeware C++ code, and an Arduino card coupled to a bluetooth module. The Arduino/bluetooth serial interface allows the user to have a connection to almost any computer and thus avoids the problem of connectivity between the computer and the peripherals

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... ch as the lock-in amplifier and the function generator. The bluetooth transmitter/receiver used is a commercial device which is robust and fast. These new features reduce the size and increment the versatility of the susceptometer for it can be used with a simple laptop. To test our instrument we performed measurements on magnetic materials and show that the system is reliable at both room temperature and cryogenic temperatures (77 K). The instrument is suitable for any physics or engineering laboratory either for research or academic purposes.