Depending on the maximum expected forces, ASTM D695 can be performed on either a single column or dual column universal testing machine such as those available in Instron's 6800 and 3400 Series.

The preferred specimen dimensions for ASTM D1621 testing are a square or circular cross-sectional area between 4 and 36 square inches and a height between 1 inch and the specimen’s width (or diameter). Note the dimensional differences between a D1621 and D695 specimen, which are both ATSM compression test standards for plastic materials. Compression platens with integral spherical seats are ideal for ensuring platen to platen parallelism, which is a requirement of the standard. Depending on your application, the following are commonly used for ASTM D1621 testing:

• Upper compression platen with integral spherical seat (diameters vary from 2 to 8”)
• Lower rigid platen of matching size
• 2601-04X series LVDT (depending on required displacement)
• LVDT mount for platens (2601-071)

• Compression platens with integral spherical seats are ideal for ensuring platen to platen parallelism, which is a requirement of the standard. The self-aligning nature of this fixture will maximize the contact area between the platen and the specimen.
• When measuring compressive displacement, ASTM D1621-16 allows for measurement using direct compression platen displacement or via crosshead extension by eliminating the effects of system compliance. If direct strain measurement is used, a displacement transducer is required to measure the distance between the upper and lower platen. The transducer must also be verified in conformance with ASTM E83 Class C or better. Instron's 2601-04x series LVDTs can mount directly on the 2501 series compression platens and are designed to measure displacement directly from the platens. To measure displacement via crosshead extension, Bluehill Universal testing software can do an automatic compliance correction to eliminate system compliance from the test curve. Please review the compliance correction whitepaper for more details. 
• If reporting the modulus calculation, make sure the extensometer and load cell are both verified in the range that the calculation is being made. Labs sometimes unknowingly report calculations outside of the verified range of their devices.
• It is important to review ASTM D1621-16 in order to fully understand the test setup, procedure, and results requirements.