Front Load Dual Sensor

INFICON Front Load Dual crystal sensors offer proven reliability and durability and have the best thermal stability of any sensor head on the market. The dual sensor provides a backup crystal and is essential for critical processes where it is desirable to have the second crystal in the vacuum chamber.

The front load design allows for easy insertion of the crystal holder in applications lacking sufficient room for side insertion. Assembled mechanically rather than soldered, parts can be replaced conveniently in the field, if necessary. Sensors can be ordered individually or in a sensor/feedthrough combination that can be either welded or assembled with compression fittings.


  • Dual crystals
  • Crystal shutter
  • Front load crystal holder
  • Easy installation
  • Available with: 2.54 cm (1 inch) bolt feedthrough and CF40 feedthrough
  • Adjustable length if ordered with compression fittings
  • No brazing required if ordered with compression fittings or welded to feedthrough
  • Sensor/feedthrough combinations available welded to customer specified lengths


Type Front Load Dual Sensor
Maximum bakeout temp with no water 130° C
Maximum operating isothermal environment temperature with minimum water flow 400 ° C
Size (maximum envelope without shutter) 1.54 in. x 3.23 in. x 1.95 in. (39.12 mm x 82.04 mm x 49.54 mm)
Water tube and coax length, “E” sensor Standard 30 in. (762 mm)
Crystal exchange Front-loading, self-contained package for ease of exchange. Shutter flips up to ease access to the holders.
Mounting Two #4-40 tapped holes on the back of the sensor body
Installation Requirements  

Qty. (1) 2¾ in. (69.85 mm) ConFlat® with 2 Microdot®, 2 pass water and air, or

Qty. (1) 1 in. (25.4 mm) bolt with 2 Microdot, 2 pass water and air.


1) Valve assembly for air—IPN 750-420-G1

2) Two oscillators or one oscillator and 779-220-G1 CrystalTwo Switch designed to interface with the deposition controller.

3) For automatic operation, the deposition process controller must be designed for the implementation of this feature.


1) Minimum water flow 150-200 cc/min, 30°C max (Do not allow to freeze.)

2) Air, 80 PSIG (5.5 bar) [552 kPa] very low volume, DO NOT EXCEED 110 PSIG (7.6 bar) [760 kPa]

Water quality Coolant should not contain chlorides as stress corrosion cracking may occur. Extremely dirty water may result in loss of cooling capacity.
Body and holder 304 Type stainless steel
Springs Au plated Be-Cu
Water tubes S-304, 0.125 in. (3.175 mm) OD x 0.015 in. (0.381 mm) Wall thickness seamless stainless steel tubing
Connector (Microdot) Stainless steel, Teflon® and glass insulated
Insulators >99% Al2O3
Wire Teflon insulated copper
Other mechanical parts 304 or 18-8 stainless steel
Braze Vacuum process high temperature Ni-Cr alloy
Crystal 0.550 in. (13.97 mm) diameter
Feedthrough Specifications 1 in. bolt and Ultra-Torr (compression fitting) terminations:  
Materials 304 stainless steel, Teflon, ceramic, beryllium nickel, VITON®
Temperature Operational environment to 300ºC with water cooling or 165° C without
Mounting 1.015 in. ±0.010 in. diameter aperture
Feedthrough Specifications CF 40 (2 3/4 in. ConFlat) welded terminations:  
Materials 304 stainless steel, Teflon, ceramic, beryllium nickel
Temperature Operational environment to 450° C with water cooling or 165° C without
Mounting Mates with 2 ¾ in. ConFlat type flanges with 1.375 in. I.D. min.


Name Description
QCM Sensor Feedthroughs QCM Sensor Feedthroughs
Front Load Dual Sensor
Part Number Description
750-420-G1 Solenoid Valve, 24V (for use with shuttered and multi-crystal sensors)


Name Description
Quartz Monitor Crystals Quartz Monitor Crystals

Spare Parts

Front Load Dual Sensor
Part Number Description
007-007 Retainer spring (for crystal holder)
007-023 Ceramic Retainer
080-018 Set screw (for female coax)
082-044 Teflon screw (for leaf spring)
750-115-P4 Coupling (installs onto bellows assembly)
750-169-P2 Bellows assembly (coupling not included)
750-171-P1 Finger spring contact
750-172-G1 Crystal holder (includes retainer spring)
750-174-P2 Female coax
750-175-P1 Insulator (underneath leaf spring)
750-188-P3 Leaf Spring
750-210-G1 Shutter module (bellows assembly, shaft assembly, and shutter assembly)
750-215-G1 Shaft assembly (part of shutter module)
750-216-G1 Shutter assembly (part of shutter module)
In-vacuum cables
321-039-G12 In-vacuum cable, 15.2 cm (6 in.)
007-252 In-vacuum cable, 30.5 cm (12 in.)
321-039-G11 In-vacuum cable, 61.0 cm (24 in.)
007-044 In-vacuum cable, 78.1 cm (30.75 in.)
007-059 In-vacuum cable, 91.4 cm (36 in.)
007-061 In-vacuum cable, 121.9 cm (48 in.) - Requires ModeLock controller
321-039-G13 In-Vacuum Cable, 154.2 cm (60 in.) - Requires ModeLock controller
321-039-G14 In-vacuum cable, 182.9 cm (72 in.) - Requires ModeLock controller
321-039-G15 In-vacuum cable, 3.5 m (137.8 in.) - Requires ModeLock controller and 4 m XIU
321-039-G16 In-vacuum cable, 4 m (157.5 in.) - Requires ModeLock controller and 4 m XIU
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