MTS Acumen - Manual (Page 153)

Changing polarity does not change the actual (electrical) polarity of the sensor or calibration; it simply
changes how data is shown. For example, consider a situation where tension is positive and the home
position is 0. If you retract the actuator 5 mm, the meters on the bottom of the screen will show +5 mm
axial displacement. However, if you change polarity so that compression is positive, the value becomes
inverted and shows -5 mm axial displacement.
Polarity in the Situational Awareness Panel
The Situational Awareness panel (SA, for short) will reflect the polarity of the signal being shown. For
example, when compression is positive, the specimen side (right side) of the SA diagram will have positive
numbers at the bottom of the diagram and negative numbers at the top. When the polarity is changed so
that tension is positive, these minus and plus signs will “switch” so that positive numbers are on the top
and negative numbers are on the bottom. As a reminder that the Signal Sense has been inverted, a minus
and plus sign appear on the right side of the frame diagram on the Situational Awareness panel. When
switching polarity, the location of specimen zero and the values and compression/tension symbols on the
fixture side of the diagram remain unchanged.
Tension and Compression Symbols
To help you understand how the polarity settings affect actuator movement when you enter a manual
command or entering setpoints, compression and tension symbols are located on either end of setpoint
sliders and manual command sliders throughout the user interface:
Tension and Compression Symbols
These symbols indicate which direction the actuator will move when you perform a manual command.
When these symbols appear next to setpoint sliders, they indicate whether moving a setpoint slider bar to
the left or right retracts or extends the actuator.
Additionally, the symbols automatically “switch” positions if the polarity is changed. Because of this, the
compression and tension symbols help you easily understand what is happening with the system regardless
of how polarity is configured.
Test and Template Considerations
While tension tests typically show positive values for displacement, force, and strain to correspond to the
pulling action being exerted on the specimen, and compression tests typically show positive values to
correspond to the pushing action on the specimen, you can use the polarity setting to view data per any
convention desired. For systems running a wide variety of tests, standard practice is to keep tension
positive.
If you are using an MTS-supplied template, you should set polarity to correspond to the template or you
may receive an error message when you try to run the test. Changing this polarity setting does not affect
calibration.
MTS Acumen ™ | 153
Best Practices for Other System Configurations and Tests