Hall measurement system with rotary magnet

Abstract

One or more embodiments are directed to a motor configured to rotate at least one magnet at a first frequency, a sensor configured to generate a reference signal of the at least one magnet's rotation, and a lock-in detection system configured to receive the reference signal, supply an excitation current at a second frequency to a device under test, measure a voltage from the device under test and demodulate the second frequency, and demodulate the first frequency from the measured voltage using the reference signal to obtain a Hall voltage associated with the device under test.

What is claimed is: 
     
         1 . A system comprising:
 a motor configured to rotate at least one magnet at a first frequency;   a sensor configured to generate a reference signal of the at least one magnet's rotation; and   a lock-in detection system configured to:
 receive the reference signal, 
 supply an excitation current at a second frequency to a device under test, 
 measure a voltage from the device under test and demodulate the second frequency, and 
 demodulate the first frequency from the measured voltage using the reference signal to obtain a Hall voltage associated with the device under test. 
   
     
     
         2 . The system of  claim 1 , further comprising:
 a control module configured to control a speed of the motor.   
     
     
         3 . The system of  claim 1 , wherein the reference signal comprises a digital signal, the system further comprising:
 a control module configured to read a Hall signal associated with the at least one magnet's rotation and generate the digital signal based on the read Hall signal.   
     
     
         4 . The system of  claim 1 , wherein the motor comprises a stepper motor. 
     
     
         5 . The system of  claim 1 , wherein the motor comprises a DC motor. 
     
     
         6 . The system of  claim 1 , wherein the sensor comprises at least one of a Hall sensor and an optical sensor. 
     
     
         7 . The system of  claim 1 , wherein the first frequency is less than the second frequency. 
     
     
         8 . The system of  claim 1 , wherein the lock-in detection system comprises an amplifier configured to supply the excitation current to the device under test and measure the voltage from the device under test and demodulate the second frequency. 
     
     
         9 . The system of  claim 8 , wherein the lock-in detection system comprises a second amplifier configured to demodulate the first frequency from the measured voltage using the reference signal to obtain the Hall voltage associated with the device under test. 
     
     
         10 . The system of  claim 8 , wherein the lock-in detection system comprises a computer configured to demodulate the first frequency from the measured voltage using the reference signal to obtain the Hall voltage associated with the device under test. 
     
     
         11 . The system of  claim 1 , wherein the at least one magnet comprises at least a first magnet and a second magnet, and wherein the first magnet is configured to be rotated by a drive supplied by the motor, and wherein the second magnet is configured to rotate on bearings following the rotation of the first magnet. 
     
     
         12 . The system of  claim 1 , wherein the at least one magnet comprises a permanent magnet. 
     
     
         13 . The system of  claim 1 , wherein the at least one magnet comprises a neodymium iron boron (NIB) magnet. 
     
     
         14 . An apparatus comprising:
 at least one processor; and   memory having instructions stored thereon that, when executed by the at least one processor, cause the apparatus to:
 receive a reference signal associated with at least one permanent magnet's rotation at a first frequency, 
 supply an excitation current at a second frequency to a device under test, cause a voltage from the device under test to be measured, 
 demodulate the second frequency from the measured voltage, and 
 demodulate the first frequency from the measured voltage using the reference signal to obtain a Hall voltage associated with the device under test. 
   
     
     
         15 . The apparatus of  claim 14 , wherein the instructions, when executed by the at least one processor, cause the apparatus to:
 receive the reference signal as a digital clock signal at the first frequency.   
     
     
         16 . The apparatus of  claim 14 , wherein the instructions, when executed by the at least one processor, cause the apparatus to:
 obtain the Hall voltage as a signal that is proportional to a product of an amplitude of the excitation current and an amplitude of a magnetic field associated with the at least one permanent magnet.   
     
     
         17 . The apparatus of  claim 14 , further comprising:
 a voltmeter configured to measure the voltage from the device under test.   
     
     
         18 . A system comprising:
 a control module configured to control a speed and direction of a motor coupled to a magnet;   a sample stage configured to apply a magnetic field associated with the magnet to a device under test and obtain an analog Hall signal; and   a lock-in detection system configured to obtain a DC Hall voltage from the analog Hall signal based at least in part on a demodulation or filtration of frequency characteristics associated with an excitation current and the applied magnetic field.   
     
     
         19 . The system of  claim 18 , wherein the lock-in detection system is further configured to obtain the DC Hall voltage from the analog Hall signal based at least in part on a digital signal representation of the analog Hall signal generated by the control module. 
     
     
         20 . The system of  claim 18 , wherein the lock-in detection system is configured to generate and provide the excitation current to the device under test.