| 摘要 |
A caliper or measurement apparatus for compressible sheet material includes first and second opposed contact faces which move relative to each other. A load cell in one face detects the load exerted there against, while a position indicator indicates the distance between faces. A microprocessor monitors load and position values continuously, corrects the load signal for noise and drift and determines whether a change in load cell output is correlated with advance of the measurement face. When a coupled load/position pattern is identified as a compression curve, the second contact face is assumed to have contacted the sheet and a thickness value is derived from the signals. Preferably, signal values are scaled and the processor operates on integral values, resulting in fast arithmetical operations that proceed in real time as the sensors are polled at a rate in excess of several kilohertz. Once contact is achieved, the processor stores load and position values which form a compression curve, and may implement further processing to produce other empirical measurements. A bulk ZLC measurement is equal to the zero-load intercept of a tangent to a linear region of the compression curve, while fixed-load relaxed measurements, such as TAPPI measurements, are advantageously taken by applying a fixed static load in the linear compression region of the specimen. All three measurements may be taken in succession as the caliper closes.
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