One of the problems that Quartz Crystal Monitors have always had is a good way to oscillate the sensor crystal. It takes a small electronic circuit to do this, and it should be located as close to the crystal sensor as possible. If you have a monitor on your vacuum system, the oscillator is the small box that is located outside the vacuum chamber, near the coaxial feedthrough. There is usually a 6 to 12-inch cable connecting the oscillator to the feedthrough and a 30-inch coaxial cable inside the vacuum system connecting the sensor to the feedthrough. All of these cables add electrical capacitance to the oscillator circuit, and this is an undesired component. Adding electrical capacitance makes it more difficult to oscillate the sensor crystal and leads to an early crystal fail condition. McVac has developed an oscillator that resides inside the vacuum chamber. The IVO-100 is TIG welded in series to the water cooling “in” line of the sensor head, typically within 6 inches of the crystal. This cuts the capacitance that the oscillator normally sees by more than 80%. McVac originally developed the IVO-100 for users that required very long cable lengths inside their vacuum chambers. However, once in place, tests have shown that crystal life was extended by up to 50%. These tests were done using dielectric materials, which are notorious for shortening crystal life. Without the added electrical capacitance load imposed by the long cable, it becomes much easier to drive the sensor crystal resulting in a significantly longer life.
The IVO-100 is water-cooled along with the crystal sensor, however, the bakeout temperature should be limited to 150 C. Maximum operating temperature inside the oscillator housing is 85 C. For many applications, our In Vacuum Oscillator is a great solution to the long-standing problem of oscillating the sensor crystal. The IVO-100 is compatible with most Monitors and controllers.
Call for Price and delivery of the McVac IVO-100 In-Vacuum Oscillator. The IVO-100 is sold as a separate component to be inserted into your existing crystal sensor water “in” line or can be ordered as a sensor package.
- P/N: IVO-100 In-Vacuum Oscillator w/ 6″ In-Vac Cable
- P/N: 700-001/IVO Single Sensor w/ In-Vac Oscillator & (1) Cables (As seen above).