MTS Series 793 - Manual (Page 123)

Pre-Calibration Considerations
MTS Series 793 Tuning and Calibration Calibration Procedures 123
Pre-Calibration Considerations
Before you start sensor calibration, be sure the following are true:
• The sensors are properly connected to the controller.
• A configuration file has been created that includes the hardware resources
associated with the sensors you want to calibrate.
• You have completed an initial, nominal tuning of the sensor channel you are
calibrating. This is especially important if you have not calibrated the sensor
before.
• The hydraulics are warmed up (see System warm-up below).
• Conditioner Gain is set to 1.
• You know your signal polarity (see below).
System warm-up
Be sure that both the hydraulic fluid and the servovalve are at operating
temperature before calibration. Remove any specimen and run the system in
displacement control for at least 30 minutes using a 80% full-scale length
command at about 0.1 Hz.
Signal polarity Some test systems are configured to extend the actuator in response to a positive
command, while other test systems are configured to retract the actuator in
response to a positive command. Conditioner polarity determines feedback
polarity.
You must know how your test system is configured so you can determine the
appropriate polarity for the values used in this chapter. The valve polarity is
established first (see
“How to Set Servovalve Polarity” on page 56).
Full-range
conditioners
All MTS Series 793 Controllers except FlexTest IIm/CTC Controllers may be
equipped with full-range conditioners (e.g. Model 493.25 DUCs). Consider the
following when calibrating sensors that use full-range conditioners:
• Full-range conditioners allow a gain/linearization calibration option which
require you to set up a linearized data table during sensor calibration.