Old dial-gauge machines still conform to ASTM C 39-94 requirements? Yes. But they can't provide a printout verifying the final reading. They can't provide information that allows the test procedure to be repeated accurately. And dial-gauge devices can't decrease the likelihood of human error by performing calculations automatically.
Two main options for upgrading screw-type or hydraulic compression testing equipment are digital-readout or fully automated systems. Both improve repeatability, measure load in small increments (for increased precision), and can be linked to a computer to print out test results.
By providing the measured rate of loading, the upgraded machines increase the likelihood that testing procedures are repeated at identical loading rates. Many software packages record the loading rate and the total load at failure, and can be customized to provide more detailed information about specimens. This information can include the age, type, and identification number of the specimen, as well as the break and cap types. Many upgraded systems print out graphs showing various details of the testing procedures. Some print out stress-vs.-time or load-vs.-time graphs.
A digital-readout system displays the load reading and can link to a computer to record and store data. This system provides much more detailed output than a dial-gauge system, usually showing load in 10-pound increments and displaying the loading rate. This gives the operator increased control over the testing process by allowing him to make corrections in his loading rate.
Fully automated testing systems do not require the operator to control the rate of loading. They only require an operator to enter a few test parameters--such as expected strength and loading rate--and specimen information--such as specimen-identification number, specimen type, and cap type and age--before placing the specimen into the machine. After the operator enters this information, the machine conducts the test. The variation that results from the operator switching to a metered rate at different initial loads and loading variability between two or more operators is eliminated. Because of this reduction of operator influence on the test results, testing labs with more than one operator benefit the most from fully automated systems.
KEYWORDS: cylinder, testing