MTS Fatigue Template - Manual (Page 83)

Description Item
Specify a number of cycles after which the specimen
is expected to be stable and beyond hardening or
softening. Cycles for Stable
Cycle
Specify a percentage used to calculate stability. Stable Cycle
Percent
Specify a percentage that is used to calculate the
stable strain range and crack initiation. Crack Initiation
Change
Specify a percentage that is used to calculate the
stable load range and specimen failure. Load Failure
Change Percent
Specify a percentage that is used to calculate if the
load control peak occurs outside the control range. Peak Load Level
Control Change
9.2.8.0 Extensometer Calibration
Extensometer verification
Extensometer calibration ensures accurate data collection. You should verify the extensometer calibration
before performing any testing. To verify extensometer calibration, set the system to load control and ramp to
zero load. At zero load, the strain extensometer is zeroed.
An extensometer includes a strain gage. You should verify its calibration before you run a test. You can verify
the calibration accuracy of a DC sensor/conditioner pair through shunt calibration. Shunt calibration works
by shunting a precision resistor across one arm of the sensor’s Wheatstone bridge. The resulting imbalance
provides a reference value that is recorded on the calibration data sheet that accompanies the sensor.
Note:
With systems that use Series 494 hardware, you can use the HWI Editor application to select the arm
of the bridge where the shunt calibration resistor will be applied.
A current shunt calibration value, taken before a test, should be compared to the shunt calibration reference
value recorded when the sensor was last calibrated. If the reference value and the current value differ too
greatly, the sensor/conditioner pair should be recalibrated to establish a new shunt reference value.
Significant variations between current and reference values can occur if the excitation voltage has drifted, or
the sensor has been damaged or has changed in some other way. It is possible to adjust excitation to
compensate for small-to-moderate changes in the shunt calibration value.
Calibration overview
The calibration process coordinates the interaction between the transducer, a DC conditioning circuit, and a
cable. Calibration of a transducer is a two-step process:
First, a specific output of the conditioner is adjusted to a specific displacement of the transducer. This is
performed by adjusting the excitation voltage and amplification (gain) of the conditioner.
MTS TestSuite 83
9.0 Transition Test Elevated Temperature Template