Inficon SQM-160, Operating Manual

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SQM-160 Operating Manual
6.2.2 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.
A somewhat more thorough diagnosis may be performed with the optional
Crystal Sensor Emulator, 760-601-G1. See
section 6.4 on page 6-15 for a
discussion of its use and diagnostic capabilities.A more detailed
troubleshooting guide is shipped with the sensor. Refer to that manual for
more detailed information in some cases
.
3. Frequency reading is
unstable or drifting a. Temperature (of the
crystal) is changing. An
AT-cut crystal frequency may
drift as much as 10 Hz/°C. a. Control the temperature of
the chamber. Check watering
cooling for flow and
temperature. Check source
to crystal distance (12 in. is
ideal).
b. Humidity (level on the
crystal) is changing. Moisture
being absorbed or exuded
from the crystal surface, b. Control the humidity of the
chamber.
4. No reading a. Settings are incorrect a. In the System Menu,
assure that Sim Mode is
OFF, Dsp Freq is ON, and F
Min/Max are set properly
(typically Freq Min=5.0 MHz,
Freq Max=6.0 MHz.)
b. Cable is disconnected or
loose b. Check setup. Ensure all
connections are fastened
securely. Make sure the
SQM-160 is properly
grounded.
c. Unit malfunctioning c. Try a different sensor
input. Contact INFICON
service dept.
Table 6-1 General Troubleshooting (continued)
SYMPTOM CAUSE REMEDY