加拿大Gem Systems
加拿大Gem Systems inc公司是专门研发和生产磁力仪的专业公司，成立于1980年。其生产的GSM-19T质子磁力仪是世界公认的磁力仪的标准系列。
质子旋进磁力仪长期以来一直是使用普遍、价格便宜的磁力仪，其用途包括矿产资源勘探，环境和工程勘探以及监测磁场变化等.

About GEM

Advanced Magnetometers since 1980GEM has had a long and growth-oriented history - starting as Geophysical Electromagnetic Systems, a consulting partnership. The company incorporated in 1980 as GEM Systems, Inc. and is now known in industry as GEM Advanced Magnetometers.
Formed by Drs. Ivan Hrvoic and Jasna Hrvoic, the company continues to be managed by Dr. Hrvoic - who contributes many years of expertise in geophysical instrumentation and electronic design.

In the late 60's and early 70's, Dr. Hrvoic worked as Senior Research Engineer by Scintrex Ltd. During this time, initial research was conducted into the feasibility and design of a Continuous Reading High Sensitivity Airborne Overhauser Magnetometer.
This work was completed by GEM in 1983 through a research grant, and led to the first of an innovative series of magnetometer / gradiometer technologies.