INFICON SID-242 Thin Film Deposition Controller - Manual (Page 69)

Chapter 4 SQM-142 Card
4-7
Replace the quartz crystal. Crystals sometimes fail unexpectedly, or exhibit erratic
frequency shifts before total failure. Depending on the material, crystals may fail well
before the typical 5MHz value. If you find that crystals consistently fail early, you may
want to set Min Frequency (see below) to a value higher then 5 MHz.
In the SQS-242 software Edit, System menu, assure that Simulate Mode is OFF, and
Frequency Min/Max are set properly for your crystals (typically Freq Min=5.0 MHz, Freq
Max=6.0 MHz). Some manufacturer's crystals exceed 6MHz when new. Setting
Frequency Max to 6.1 Hz will correct that problem, with no effect on measurement
accuracy. Assure that the proper sensors are enabled, and assigned to the desired
output.
Close the Edit, System menu and select View, Sensors to show sensor frequency and
% Life. While not depositing, observe the % Life display for each active sensor. The
value should be stable, between 20% and 100%.
If the % Life reading is zero or unstable: Recheck the wiring from the sensor to the
SQM-242, and verify that the system is properly grounded. Also check that the
crystal is seated properly in the sensor head.
Swap the sensor to another SQM-242 input. If both SQM-242 inputs show zero or
unstable readings, the problem is almost certainly a wiring or sensor problem.
If the % Life is less than 50%: Replace the crystal and assure that % Life is near
100%, very stable. If % Life is not near 100%, check the Frequency Min/Max limits.
If the problem is not corrected: Referring to Section 4.0, disconnect the 6” M/F BNC
cable from the feedthrough. A test crystal and BNC barrel adapter is supplied with
each Sigma oscillator. Attach the barrel adapter and test crystal to the 6” BNC cable
as show below.