INFICON SQM-242 Thin Film Deposition Controller Card Operating Manual - Manual (Page 58)

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SQM-242 Operating Manual
7.1.2 Troubleshooting Sensors
NOTE: Many sensor head problems may be diagnosed with a DMM (Digital
Multi-Meter). Disconnect the short oscillator cable from the feedthrough
and measure the resistance from the center pin to ground. If the reading is
less than 10 megohms, the source of the leakage should be found and
corrected. Likewise, with the vacuum system open check for center
conductor continuity, a reading of more than 1 ohm from the feedthrough
to the oscillator indicates a problem. Cleaning contacts or replacing the
in-vacuum cable may be required.
5. Poor rate control. a. Control loop parameters
improperly selected. a. Test to ensure a stable rate
is possible in manual mode.
Refer to the instruction
manual section on tuning
control loop parameters.
b. Electron beam sweep
frequency "beating" with the
SQM-242's measurement
frequency. b. Adjust the sweep
frequency so it is not a
multiple of the SQM-242’s
measurement frequency.
c. Inadequate resolution. c. Low density materials
cause little frequency change
per angstrom of thickness;
hence low resolution.
Increase the measurement
period.
NOTE: QCM resolution is affected by material density and measurement period. Low
density materials cause little frequency change per angstrom of thickness; hence
low resolution. Increasing the measurement period significantly increases QCM
resolution.Increasing the filter value only increases the display resolution.
Measurement Resolution @ Density = 1 g·cm
−3
Table 7-1 General Troubleshooting
SYMPTOM CAUSE REMEDY