For automatic and fast magnetic field measurements and data collection on magnetic beam transport elements a computerized high precision measuring machine is in operation.

For the mechanical part the measuring machine consists of a probe positioning device sliding on compressed air bearings without mechanical contact or hysteresis over a precisely flat machined granite block. This machine can move the measuring probe - a Hall- probe in general, but coil systems could be used as well - on 5 axes, 3 cartesian and 2 circular, by means of stepping motors, i.e. it has 5 degrees of freedom.

The electrical part consists of position detecting and display units, stepping motors ( with motor driving units ), and a computer system with DVMs. In general a Hall-probe serves as a magnetic field sensor, and in this case a constant current source will be used.

A Hewlett-Packard computer system HP 1000 A-900 under the operating system RTE-A controls the measurement process and takes the data under real time conditions.

The measurements are performed in a so called flying mode. The computer programs make use of position pulses, which are transmitted every 10 microns by the position detecting system ( Inductosyn ) during the motion of the machine along the axis of measurement, whose logical name is S-axis. These pulses act as interrupt signals, which cause the main program to be interrupted and the driver subroutine of the measuring system to be called. The current position will be read and at the predetermined measurement positions the DVM will be triggered, which in turn reads the Hall- probe voltage and proceeds it back with another interrupt signal to the computer.

The user may choose any three axis out of the five ones. But in most cases field maps are measured in cartesian coordinates. The computer drives the machine along the axis of measurement, the S-axis, and takes the Hall-probe voltage at each measurement position. These raw data are stored in an array in the internal memory of the computer. At the end of the S-path the machine stops and then the DVM values will undergo several error detecting procedures, the appropriate values will be converted into the magnetic induction values in Gauss units, and finally the values will be transferred onto a data file. Then the machine has to go into the next position of the second axis, the T-axis, where the measurements along the next line will continue. When the fieldmap has been finished in this position of the third axis, called the U-axis, the user may proceed to the next U-position and then take the next fieldmap. In this way magnetic field values can be measured in a volume.

The position of the measuring machine in the cartesian axis can be determined to an accuracy of total 0.01 mm . The Hall-probes have been calibrated in a highly homogeneous magnetic field against an NMR-probe. The calibration data, Hall-probe voltage and magnetic induction, have been fitted by a polynomial function whose degree has been chosen according to the criterion of the root of minimum squares of error. Thus an accuracy of the magnetic induction measurement of +- 1 Gauss can be achieved.

To give an example of the speed of the fieldmapping: in average the measuring time of a fieldmap containing 7'500 measurement position takes about 20 min.

A new measuring machine control system is in operation since 2002.