Measuring magnet field strenght

[Boris8135]

Hello
I work for a service company and we are now starting on servicing servo motors.
But here is the problem. The AC servo motor has a permanent magnet rotor. When I disassemble the motor there is a possibility of weakening the magnetic field strength of the rotor. How can I measure the rotors field strength before and after .
I thought about connecting the servo to an other motor, then starting the other motor and measuring voltage of the servo. if the rotor lost his "magnet strength" the voltage  will be lover then  before.
Is there maybe another  more precise  way??
Regards
Boris

[Ray.R]

Have you looked into Hall Effect Sensors?

Have a look at this article: http://ieeexplore.ieee.org/Xplore/login.jsp?url=/iel5/77/29325/01325161.pdf?arnumber=1325161

http://ieeexplore.ieee.org/iel5/77/29325/01325161.pdf?arnumber=1325161

and this one: http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=RSINAK000077000008086101000001&...

http://link.aip.org/link/?RSINAK/77/086101/1

and this one: Quite a bit elaborated..

The magnetic field is measured by 3 orthogonal axes of Hall effect probes.

http://www.adc9001.com/documents/company/publications/papers/magnetic_field.pdf

[sasko]

Hello

Take a look at www.senis.ch

They have a lot of small 3D Hall probes

Sasa