A precise method to measure horizontal field components in dipole magnets

The precise measurement of horizontal field components in dipole magnets has been investigated experimentally. Measuring devices have been evaluated in detail, results of these tests are presented and a basic method of measurement is proposed. Three Hall-generators and two electrolytic level sensors are mounted orthogonal to each other onto a manually adjustable measuring head. A better understanding of the relevant effects on these devices did lead to a markedly improved accuracy of such measurements. With proper calibration, horizontal field components in the microtesla range can be resolved at vertical field levels of 1-2 T. Of particular importance for such applications is that the alignment of Hall-generators in field direction shows a slight but significant field dependence (Hall offset angle) which has to be taken into account.