Common Problems

1. See the problems in the previous section.

2. The field feedback signals jump to +10V or -10V when enabling the field feedback system, and stay there afterwards.

   This is usually caused by a wrong state of the field feedback system. For example, wrong sign of the feedback settings (XCOS, YCOS) can cause a positive feedback such that the signals are stablized to the satuated values.

3. The field feedback signals oscillate between +10V or -10V when enabling the field feedback system.

   This is also caused by a wrong state of the field feedback system. Because we are using two dimensional field feedback, wrong sign of the feedback settings (XSIN, YSIN) will cause the longitudinal and transverse components of the field interfering with each other through a positive feedback so both are not stablized.

4. The field feedback signals are stablized at a small but non-zero value.

   This means the field feedback system is working properly and in principle should not affect the measurement. However, a non-zero offset of either of the signals may cause a non-linearity between holding field and the compensation coil current, which should be avoided in high precision polarization measurements. With the field feedback system in `Bypass' mode, you can adjust the screws on field feedback chassiss to adjust the `XOFFSET' and 'YOFFSET', meanwhile use a scope to measure the two field feedback signals from magnetometer sensor until they are stablized to zero.