| 摘要 |
The method comprises the step of causing magnetic properties of the strip member to be varied at the point along the strip to be measured. A magneto-acoustic pulse is injected one end of the strip and the time (t1)- is detected at which the pulse reaches the point. A second pulse is caused to pass along the strip from its other end, and time (t2) is measured corresp. to the time required for that pulse to reach the point. The times t1 and t2 are used to calculate the position of the point independently of any expansion of the strip due to temperature variations.
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