937B Controller Instruction Manual
pg. 47
7.2.3
Managing Contamination in a Cold Cathode Sensor
Do not operate a Cold Cathode gauge at pressures above 10
-3
Torr for extended periods. This will
increase the likelihood of contamination due to higher sputtering rates. If pressure readings appear
erratic, the sensor may be contaminated. In such a case, it should be visually inspected and, if
contamination is visible, the internal components should be cleaned or replaced using an Internal Rebuild
Kit.
7.2.4
Connecting the Series 431/422 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. On sensors with CF flanges, a ground
lug on a flange bolt could be used to attach a ground if necessary.
Connect the cables to the sensor and to the Controller before turning ON. Connections on the rear panel
of the Controller are H.V. (SHV connector) and Ion Current (BNC connector). The sensors also have H.V.
and current connections. Note that some Series 422 sensors have LEMO connectors rather than SHV
and BNC connectors.
If there is any potential for strain on the cable, use separate strain relief to avoid damage to the sensor,
cable, or the Controller.
Cables are available from the factory in standard lengths of 10, 25, 50, and 100 feet and in custom
lengths up to 300 ft.
7.2.5
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.
7.3 Installing Hot Cathode Sensors
7.3.1
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 ensure the mechanism cannot inadvertently damage the sensor.
7.3.2
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.
7.3.3
Orienting a Hot Cathode Sensor
A Hot Cathode sensor can be installed and operated in any direction without compromising the gauge
accuracy. However, it is recommended that, whenever possible, the sensor be installed with the vacuum
port facing down to keep contaminants from falling into the sensor.