Vibrating-sample magnetometer
A ferromagnetic sample is mounted on a vertical rod and
positioned between the pole shoes of a magnet.
The rod is driven by a transducer that is synchronized by the reference signal
received from the lock-in amplifier.
A set of pick-up coils produce a signal that is proportional to the magnetization of the sample, and the strength of the magnetic field is measured with a Hall probe. The lock-in amplifier filters the pick-up signal to produce a DC output voltage which corresponds to the signal component with proper frequency and phase.
The output signal of the lock-in amplifier is sampled with a 12-bit ADC. The supply that powers the magnet is regulated with a 12-bit DAC; the polarity is switched using a programmable parallel interface (PPI). The same PPI is used to interconnect the pick-up coils in such a way that the x, y and z components of the magnetization can be measured independently.
ADC, DAC and PPI are parts of the LabMaster interface card in the personal computer. The gauss meter is connected to the serial port of the personal computer.
The magnetization measurements are completely computerized using special features of the data acquisition program CONTROL.
A set of pick-up coils produce a signal that is proportional to the magnetization of the sample, and the strength of the magnetic field is measured with a Hall probe. The lock-in amplifier filters the pick-up signal to produce a DC output voltage which corresponds to the signal component with proper frequency and phase.
The output signal of the lock-in amplifier is sampled with a 12-bit ADC. The supply that powers the magnet is regulated with a 12-bit DAC; the polarity is switched using a programmable parallel interface (PPI). The same PPI is used to interconnect the pick-up coils in such a way that the x, y and z components of the magnetization can be measured independently.
ADC, DAC and PPI are parts of the LabMaster interface card in the personal computer. The gauss meter is connected to the serial port of the personal computer.
The magnetization measurements are completely computerized using special features of the data acquisition program CONTROL.