Knowing the electrical offset of the storage ring beam position monitors (BPM) to an adjacent quadrupole magnetic center is important in order to correct the orbit in the ring. We describe a simple, fast and reliable technique to measure the BPM electrical centers relative to the quadrupole magnetic centers. By varying individual quadrupole magnets and observing the effects on the orbit we were able to measure the BPM offsets in half the horizontal and vertical BPMs (48) in the ALS. These offsets were measured to an accuracy of better than 50μm. The technique is completely automated and takes less than 3 hours for the whole ring.
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