Autotune function

The XTC/2 and XTC/C group can control vacuum coating sources and up to three different coatings of a process (not to be confused w/ith nine different coating programs). In the case of XTM/2, XTC/2 and XTC/C units, the AutoZero and AutoTune functions are not available, and measurement with several sensors simultaneously as well as simultaneous control of two vacuum coating sources are not possible. 

Before sample analysis, the tuning of the MS was checked by using the autotune function and run the BFB check sample. The used ISQ MS met the tuning criteria for BFB listed in the method (see Figure 4.7). 

This method can be extended to evaluate models with more parameters and with diHerent kinds of transfer functions (e.g., underdamped second-order lag) by using hysteresis in the relay feedback or by inserting an additional dead time in the loop to produce a limit cycle with a different frequency. The two autotune tests give four equations so four parameters can be evaluated. 

However, the IC/5 offers all comfort functions available today measurement with up to eight sensors with AutoZero and AutoTune as virell as capability of simultaneous control of two evaporator sources. Moreover, it offers 24 material programs, with which 250 coatings in 50 processes can be programmed. To simplify operation and avoid errors, the unit also has a diskette drive. All types of crystal holders can be connected here. The thickness resolution is around 1 A, the rate resolution for rates between 0 and 99.9 A/s around 0.1 A/s and for rates between 100 and 999 A/s around 1 A/s. A particularly attractive option offered by the IC/5 is a microbalance... 

Simulate several first-order lag plus deadtime processes on a digital computer with a relay feedback. Compare the ultimate gains and frequencies obtained by the autOtune method with the real values of and Ku obtained from the transfer functions. 

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