With the addition of the Feedback Control software upgrade, any Hysitron system can be advanced from its inherent open-loop testing regime. Feedback control testing provides precise control of the nanoindentation probe in both load and displacement controlled modes.

The Feedback Control package is a software-driven feedback system utilizing a high-frequency feedback loop that allows for true load and displacement control. The tunable proportional, integral, derivative and adaptive gain parameters allows the user to adjust gain setting based on particular sample properties to attain optimal feedback response on any material.

By increasing the control of the nanoindentation probe the user can achieve precise load or displacement values while more accurately investigating sample qualities such as creep, adhesion and general polymer testing.

Systems equipped with the feedback control package and TriboScan 8.0 or later will automatically be upgraded to feedback control with nanoscratch. Given the system is equipped with a lateral force transducer, the feedback control nanoscratch will provide the same quality of closed-loop testing for friction and delamination studies with nanoscratch testing.

All performech™ control unit equipped systems (TI 950 TriboIndenter^®, TI 750 Ubi™, TS 75 TriboScope^®, PI 95 TEM PicoIndenter^®, and PI 85 SEM PicoIndenter^®) include the Feedback Control package standard.

Feedback control testing includes a lift height parameter, which is unavailable with open-loop testing. The lift height withdraws the probe (10 nm - 2 μm) from the sample surface following the drift correction but before the test is begun. The test is then started as the system starts stepping down from the lift height location until the sample surface is identified and the test is begun. Using a lift height allows the system to more accurately identify the sample surface and prevents the test from beginning with the probe settled into the sample surface following the drift correction procedure.

The Feedback Control testing mode features:

• Feedback control is available for all Hysitron nanomechanical testing instruments
  
• Improved quasistatic testing performance for ultra-thin films and soft materials
  
• Self-tuning adaptive control responds to variations in material stiffness
  
• Provides superior force sensitivity for study of precontact tip-sample interaction
  
• Creep tests for investigation of time-dependent or viscoelastic properties of materials
  
• Stress-relaxation tests for investigation of viscoelastic properties of materials