System Info Window
The System Info window provides basic system information about the Homer Analyzer/Autotuner. The window can be opened by clicking the View|System Info menu item or the button on the Standard toolbar (Fig. 15).
In the case of Homer Analyzer, a single-page window opens with the page titled Homer; in the case of Homer Autotuner, a multipage window opens with pages titled Homer, Tuner, Motors, Autotune and Sketch. Items shown in the Autotune page can be clicked and modified (a fact indicated by a hand-shaped mouse cursor when hovering over them).
Homer and Tuner Pages
The Homer page (Fig. 34) displays identification, waveguide size and nominal frequency of the Homer Analyzer.
Fig. 34. Homer and Tuner pages of System Info window.
The Tuner page displays identification information, waveguide size and nominal frequency of the Homer Mototuner. In the case of the compact, one-piece Autotuner, the Tuner page is identical to the Homer page except for the missing Peak power. Also, Nominal frequency may differ for the Analyzer and the Tuner.
Motors Page
The Motors page (Fig. 35) displays basic parameters characterizing tuning stubs (motors) motion. An approximate full travel time is computed as (Max Steps)/(Pull-in rate).
Fig. 35. Motors page of System Info window.
Autotune Page
Thanks to the fact that the Homer Analyzer measures complex reflection coefficient, the autotuning process is not a trial-and-error procedure: on the contrary, the process employs a systematic, predictive algorithm which, based on a single measurement performed with arbitrarily inserted tuning stubs, computes new, match-ensuring stub positions. (Due to limited measurement accuracy, sometimes two or three cycles are required.) The computations take a fraction of a second, so the speed of the process depends essentially on the motor speeds.
The autotuning process is controlled by several parameters. The Autotune page of the System Info window (Fig. 36 left) lists those which the user can modify. This is done by simply clicking the corresponding item.
For the case of the HoSim simulation (Fig. 36 right), please also refer to Truncating Matchable Area and Real Tuner Performance.
Fig. 36. Left: Autotune page of System Info window. Right: The page appearence in the HoSim simulation program.
Target [milliunits]
Target is the desired goal reflection coefficient magnitude to be attained by impedance matching. The Target value is to be entered in milliunits (1 milliunit = 0.001 in terms of reflection coefficient magnitude).
In most applications, a perfect match is desired. To strive for a perfect match, set Target to zero, which is also the default value.
There are, however, microwave installations (notably some plasma applicators) that may work better when autotuning is not aimed at perfect match but at a reflection coefficient with a nonzero magnitude. To achieve it, set Target to the desired value. The autotuning mathematics (computation of stub positions) proceeds until the magnitude of the input reflection coefficient differs from the Target value by less than the Tolerance (described below).
The Autotuner power-up value of Target is controlled by the following line in the internal Tun.cfg configuration file:
Targ_mU=0; Target [milliunits] for autotuning
Mathematically, the tuning algorithm finds the positions of two of the tuning stubs to achieve a perfect match, and then “spoils” this match by the third, unused, stub. The phase angle of the resulting reflection coefficient is not (cannot be) controlled by this method.
If the Homer is not equipped with the Defined Mismatch Tuning option, the Target value will be ignored (internally set to zero).
Tolerance [milliunits]
Tolerance (rT) is the maximum acceptable deviation of the input reflection coefficient magnitude from the desired Target value. It can be envisaged as a circle with a radius rT around the target reflection coefficient (also see figures in section Hysteresis). If the input reflection coefficient is within this circle, the stubs will not move. Set Tolerance to a value different from zero if you want to prevent stubs from incessant fine-tuning.
Similarly to Target, the Tolerance value rT is to be entered in milliunits. The default value is 25 milliunits.
The Autotuner power-up value of Tolerance is controlled by the following line in the internal Tun.cfg configuration file:
Toler_mU=25; Tolerance [milliunits] for autotuning
Tuning pause [ms]
Sometimes you may wish to introduce a delay between two consecutive autotuning attempts to prevent stubs from frequent movements. This can be done by setting a non-zero Tuning pause. The value is entered in milliseconds between zero and 2550; it will be rounded to tens of ms. The default value of Tuning pause is zero, which ensures the fastest possible tuning.
The actual delay in milliseconds can be longer depending on how long one measurement and stubs movement takes.
The Autotuner power-up value of Tuning pause is controlled by the following line in the internal Tun.cfg configuration file:
Pause_10ms=20; Minimal interval n x 10ms between tuning steps
In this example the Tuning pause will be 200 ms. The value can range from zero to 255.
Starting with HomSoft version 5.0.3.0, the Tuning pause parameter replaces the deprecated previous Skipped measurements.
(Skipped measurements)
Please note that this parameter applies to older HomSoft versions (5.0.2.0 and less). In more recent versions, Skipped measurements is replaced by the more exact Tuning pause.
Here is the original text:
Sometimes you may wish to introduce a delay between two consecutive autotuning attempts. This can be done by making a number of measurements without tuning after each autotuning step. The number can be entered as Skipped measurements. The higher the number, the longer the delay. The default value of Skipped measurements is 1. The lowest possible value is zero (tuning after each measurement).
The actual delay in milliseconds depends on how long one measurement takes.
The Autotuner power-up value of Skipped measurements is controlled by the following line in the internal Tun.cfg configuration file:
Skip=1; Number of skipped measurements
Smoothing count
Smoothing is a floating average procedure applied to reflection coefficients (and frequency) in an attempt to reduce the undesirable effect of glitches (short-lived deviations) in the reflection coefficient on tuning behavior. Tuning in the case of smoothing is based not on the current results but on the mean value of Na previous results, where Na is the smoothing count.
Typical examples where increased smoothing count may be beneficial:
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Mostly homogeneous substance moving on a conveyor belt, occasionally containing a metallic object.
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A liquid flowing through an applicator, occasionally containing air bubbles.
The default value of smoothing count is 1.
The Autotuner power-up value of smoothing count is controlled by the following line in the internal Tun.cfg configuration file:
Smooth=1; Number of averaged measurements taken for one tuning step
Smoothing should be applied judiciously and well tested because under certain circumstances it may not work as expected. To smooth out regular oscillations of the reflection coefficient (and the incident power), consider using proper sampling mode and timing instead.
Wait if RF power is low
When this parameter is set to YES (default), autotuning will be suspended when the incident microwave power is below a predefined Low Signal level. As soon as the power increases above that level, autotuning will resume.
When Wait if RF power is low is set to NO, autotuning takes place regardless of the microwave power level. This may be useful, e.g., for checking motors without microwave power (tuning based on noise).
The Autotuner power-up value of Wait if RF power is low is controlled by the following line in the internal Tun.cfg configuration file:
WaitRF=TRUE; Suspend tuning when RF power is absent or too low
For details about Low Signal level and its setting, see Low Signal Warning in section Homer Error Byte.
Tuning delay
(Applies to HomSoft versions starting 5.0.3.0)
When power supply voltages and currents are applied to a magnetron, the magnetron may need some time to reach stable operational state. During the transient period, tuning may become erratic. To avoid this, the user may postpone the start of tuning by a Tuning delay. The delay is measured from the instant the incident power rises above the Low Signal level.
The tuning delay is expressed in terms of a 5-bit number (0…31), representing the number of elementary delays applied. The elementary delay is defined in the internal Tun.cfg configuration file; the default is 250 ms. For instance, a Tuning delay value of 12 represents the delay 12 ´ 250 ms = 3 seconds.
The default value of Tuning delay is zero.
The Autotuner power-up values of Tuning delay and the elementary delay are controlled by the following lines, respectively, in Tun.cfg:
Delay5b=0; Tuning delay after power onset in steps DelayStep_ms
DelayStep_ms=250; Step of tuning delay after power onset
The Low Signal level of incident power is controlled by the following line in the internal Hom.cfg configuration file:
LowPowLvl_W=100; Incident power threshold for "Low Signal" condition
For more details, see Low Signal Warning in section Homer Error Byte.
Hysteresis
See the Hysteresis section.
Max tune Mag [milliunits]
This value truncates the matchable area to avoid excessively high-reflecting loads that, when matched by the tuner, could result in arcing.
In the live operational HomSoft version, Max tune Mag is a read-only quantity. For details, please refer to Truncating Matchable Area. For Homer units with Server versions older than V60, the displayed value is “Unknown”.
In the HoSim simulation, the value can be edited after clicking the item. For details, please refer to Studying Matchable Area.
[Defaults]
Click Defaults to set the autotuning parameters to their default values. In the live operational HomSoft version, the Max tune Mag will not be affected.
Sketch Page
The Sketch page (Fig. 37) displays relevant mechanical dimensions of the Autotuner, including the Analyzer calibration (CAL) plane location (not important for the user), the location of the input reflection coefficient reference plane (GI) and the default location of the load reflection coefficient reference plane (GL).
