Dakota Ultrasonics PR-82 User Manual

Page 29

PR-8

Sonic Tester

An additional important consideration when measuring laminates, is that

any included air gaps or pockets will cause an early reflection of the

ultrasound beam. This effect will be noticed as a sudden decrease in

thickness in an otherwise regular surface. While this may impede accurate

measurement of total material thickness, it does provide the user with

positive indication of air gaps in the laminate.

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Measuring cylinder walls & head ports

Cast iron/aluminum typically vary in consistency from manufacturer to

manufacturer and batch to batch. The nickel content will also vary in cast

iron blocks. Therefore, the user should perform a calibration on the

block/head to be measured. This is commonly done, with a one point

calibration (refer to page 14), by finding an area on the test piece that can

be measured with a set of calipers (Typical locations are at the top of the

block between two cylinders, or any other location with two parallel

surfaces). A two point calibration (refer to page 16) can also be performed

by measuring two points on the test piece, with different thicknesses, that

are representative of the actual range to be tested. For Example, if you

expect to measure a range from .200” - .050”, the hi and low calibration

points should be representative of this range (refer to page 13).