of the coil and the B field. However, N and A are often unnecessary if the VSM is properly calibrated. By varying the strength of the electromagnet through computer software, the external field is sweeped from high to low and back to high. Typically this is automated through a computer process and a cycle of data is printed out. The electromagnet is typically attached to a rotating base so as to allow the measurements be taken as a function of angle. The external field is applied parallel to the sample length and the aforementioned cycle prints out a hysteresis loop. Then using known magnetization of the calibration material and wire volume the high field voltage signal can be converted into emu units - useful for analysis. Advantages and Disadvantages The precision and accuracy of VSM's are quite high even among other magnetometers and can be on the order of ~ emu. VSM's further allow for a sample to be tested at varying angles with respect to its magnetization letting researchers minimize the effects of external influences. However, VSM's are not well suited for determining the magnetization loop due to the demagnetizing effects incurred by the sample. VSM's further suffer from temperature dependence and cannot be used on fragile samples that cannot undergo acceleration (from the vibration). References See also Magnetometer Alternating (Field) Gradient Magnetometer (AFGM or AGM) SQUID Magnetometer American inventions Magnetic devices Measuring instruments Magnetometers