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Speed Verification
What are the Standards for Speed Verification?
Currently there are no national or international standard methods for verifying
the accuracy of the speed of a materials testing machine or instrument. To fill this void,
Instron® has developed its own rigorous methods for speed verification. Fully compliant
with ISO/IEC 17025 (NVLAP Lab Code 200301-0), and using time and distance standards traceable to
National Standards, Instron speed verification provides assurance that your machine is
operating properly and that your test data is valid.
Do I Need to Verify Speed?
Some test methods define the testing speed and the speed accuracy
requirements and some do not. While the particular testing speed chosen is not always
a critical parameter, it is often important, and always good testing practice, to ensure
that the speed is constant, stable, and repeatable. These reasons alone cause many users
to request speed verifications of their testing machines. Other applications, where it
is known or suspected that the material or component under test is strain-rate or speed
sensitive, are more obvious candidates for requiring speed verification. Some examples
include composites, carbon-fiber composites, ceramics, and liquid crystal polymers.
If you are required to report test speed with your results, or if you are concerned with
the consistency of results between machines or over time, good practice indicates that
the machine's speed be verified. There are some applications where none of the above is a concern.
For these, speed verification is probably not worth doing.
What Does Speed Verification Tell Me?
- Standard Verification: The standard speed verification measures the
average speed between two positions. The crosshead or actuator is allowed a short time to
accelerate to the set speed, then an accurate displacement reading and time reading are taken.
A second set of displacement and time data points are taken after a specified travel or time
(typically 2 to 4 inches, or 30 seconds). These parameters are used to ensure a high level of
accuracy in the speed measurement. This verification will tell you, under no load conditions,
how closely matched your actual speed is to your set speed. You will also determine repeatability,
since each speed is run three separate times. The initial velocity profile of the crosshead,
minute fluctuations of speed during distance traveled, or speed accuracy under loading conditions
will not be characterized.
- Advanced Verifications: For more demanding or critical applications, it can
be useful to characterize the machine's performance at the initiation of the test and while
applying forces similar to the actual test forces.
Specifications
- Minimum Speed: none (extra charge may apply for speeds less than 1 mm/min)
- Maximum Speed: 1250 mm/min
- Displacement Accuracy of the Verification Standard: 5 - 10 microns, depending on the device
- Time Accuracy of the Verification Clock: 10 ms
- Accuracy of the Speed Measurement: 0.5 % of reading
- Verification to Higher Accuracy or Higher Speeds: consult factory
- Speed Under Load: consult factory
How Can I Improve the Management of My Lab's Calibration Program?
Instron can make life easier for you.
- We will store all relevant information about your equipment and site in our database.
That allows us to keep track of recalibration dates (specified by you),
so we can call ahead of time, and schedule convenient and timely recalibrations.
- When the verification is complete, the Instron engineer can print the certificate and data report
on-site before he leaves.
- The data and certificate are electronically backed up in a secure database at the Instron factory
and can be retrieved, if necessary.
- Instron's highly trained calibration engineers know your equipment. They can identify potential problems early, perform preventive maintenance, and understand proper use and handling of your equipment.
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