CSI-235 (Compression Load Deflection Tester )
This apparatus provides means of measuring the load necessary to deflect a sample 25 and 65 percent and to measure the thickness under fixed loads.

For Test Method D3574, Test C, the force is measured at 50% compression exerted over the entire surface of the test sample.

The unit consists of a flat circular indenter foot of 203-mm diameter (323 cm sqr.) connected to a universal swivel joint; a load measuring device; a reference scale to determine the distance between the indenter foot and the platform; and a platform to support the specimen on a level horizontal plate which is perforated with 6.5-mm (0.24 to 0.20 inch) holes on 20-mm (0.75-inch) centers to allow for rapid escape of air during the test.

The unit for manual operation is a handheld lever to measure the force in grams or kilograms to compress the specimen twenty-five percent of its thickness without removing the specimen, increase the deflection to sixty-five percent deflection noting final load.

References:
ASTM D 1056 Section 17, D 1564 Section 19
ASTM D 1565 Secction 12, D 3574 test B1, B2, and C.