946 Controller Instruction Manual
pg. 67
7.1.5 Connecting the 423 I-Mag Sensor
Mount the sensor to a grounded vacuum system. KF 25 or KF 40 flanged sensors must be attached with
a conductive, all-metal clamp to ensure the sensor body is grounded.
If the I-Mag Sensor has a CF flange, remove the magnet first to allow clearance for bolt installation. To
remove the magnet, undo the two Phillips head screws in the center of the magnet housing. When
replacing the magnet, note that it is keyed to the sensor body to protect the feed-through pins from
damage. The pins should be straight and centered.
Connect the cable to the sensor and to the Controller before turning ON. Tighten the thumbscrew on top
of the cable to make sure that it is securely in place.
7.2 Installing Hot Cathode Sensors
7.2.1 Over Pressure Conditions
Danger of injury to personnel and damage to equipment exists on all vacuum
systems that incorporate gas sources or involve processes capable of pressuring the
system above the limits it can safely withstand.
For example, danger of explosion in a vacuum system exists during backfilling from
pressurized gas cylinders because many vacuum devices such as ionization gauge
tubes, glass windows, glass belljars, etc., are not designed to be pressurized.
Install suitable devices that will limit the pressure from external gas sources to the level
that the vacuum system can safely withstand. In addition, install suitable pressure relief
valves or rupture disks that will release pressure at a level considerably below that
pressure which the system can safely withstand.
Suppliers of pressure relief valves and pressure relief disks can be located via an online search.
Confirm that these safety devices are properly installed before installing and operating
the product.
Ensure the following precautions are complied with at all times:
(1) the proper gas cylinders are installed,
(2) the gas cylinder valve positions are correct on manual systems,
(3) and the automation is correct on automated gas delivery systems.
7.2.2 Locating a Hot Cathode Sensor
Locate the sensor in a position appropriate for the measurement of process chamber or manifold
pressure. Installing the sensor away from pumps and gas sources gives the most representative pressure
measurement. In the case of a nude sensor, ensure that there is nothing in the system or mounting
location that could damage the electrode structure. Special consideration should be given to any moving
mechanism within the vacuum system to insure the mechanism cannot inadvertently damage the sensor.
7.2.3 Preventing Contamination in a Hot Cathode Sensor
Locate the sensor where contamination is least likely. For example, if the sensor is mounted directly
above a source of evaporation, the vapor could contaminate the structure or feed-through and cause
calibration shift.