Inventors:
Roberto Capriotti - Farmington MN
Mizanur Rahman - Minneapolis MN
International Classification:
G08B 2100
Abstract:
A sensor assembly and method of forming the sensor assembly for sensing count and tamper, where the count is related to an energy field having a gradient along an axis of sensitivity and where the tamper is related to a static energy field and where the energy comprising the static energy field is the same type as the energy comprising the energy field having a gradient, includes an energy gradient detector that has at least a first sensor spaced apart from and communicably coupled to a second sensor along the axis of sensitivity. A static energy detector that has at least a first shielded sensor, the shielded sensor being substantially shielded from the energy field having a gradient and from the static energy field. A second unshielded sensor is communicably coupled to the shielded sensor. The invention further includes a method of detecting a spatially varying magnetic field.