A system for measuring gas density in a vacuum includes a gauge, a housing for containing the gauge, and a magnet secured to an exterior surface of the housing. The magnet is a flexible magnetic strips, and positioned around the exterior surface of the housing. The gauge includes grid insulator posts extending longitudinally along a tubular section of the housing, and the magnet is secured to the exterior surface of the housing adjacent to the grid insulator posts, and oriented transversely to the grid insulator posts. The magnet is a flexible magnetic strip, and a clamp secures the magnet to the exterior surface of the housing.