Appendix C
Troubleshooting
Defective crystal or improper software setup cause most SQM-242 problems. Follow
the procedures below to identify and correct common problems
No Readings:
Be sure that the card is installed properly in Windows. Verify that the cards show
properly in Windows Device Manager, as discussed in Chapter 1.
The SQM-242 CoDep program, View Card Setup screen must show a non-zero Card
Revision for each installed SQM-242 card. If not, follow the installation instructions in
Chapter 1. Also be sure that Freq. Max = 6.1MHz, Initial = 6.0MHz, and Min = 5.0MHz.
Crystal Fail or Erratic Readings from Sensors:
Verify that the sensors, oscillator and cabling are connected as shown in Section 1.
Disconnect the deposition source supply. This eliminates the possibility that a noisy
source or poor loop tuning is causing an unstable PID loop.
In the SQM-242 CoDep program, select View Readings. Since a QCM is basically a
frequency counter, we will use the measured frequency for troubleshooting.
A test crystal is supplied with each Sigma oscillator. Disconnect the 6” M/F BNC cable
from the feedthrough and attach the 5.5 MHz test crystal to the 6” BNC cable.
The frequency should read about 5.5 MHz, very stable. If not, move the cabling to a
different SQM-242 input. If there is still no frequency reading then the cable and
oscillator assembly may be bad. If possible, test the assembly on another QCM. Or try
a known good cable and oscillator assembly on the SQM-242.
Once you have a stable 5.5MHz reading, reconnect the 6” BNC cable to the sensor
feedthrough. If there is no reading or an unstable reading, replace the quartz crystal.
Crystals sometimes fail unexpectedly, or exhibit erratic frequency shifts before total
