946 Controller Instruction Manual
pg. 68
7.2.4 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.
7.2.5 Connecting a Hot Cathode Sensor to the Vacuum System
Verify that the vacuum port to which the HC sensor is mounted is electrically
grounded. It is essential for personnel safety as well as proper operation that the
envelope of the sensor be connected to a facility ground.
Be aware that an electrical discharge through a gas may couple dangerous high voltage
directly to an ungrounded conductor almost as effectively as would a copper wire
connection. Personnel may be seriously injured or even killed by merely touching an
exposed ungrounded conductor at high potential. This hazard is not unique to this
product.
MKS sensors are available with either a CF type metal sealed flange, a KF type flange, or tubulation.
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.
Note:
Attaching tubulated sensors with compression type (quick connect) adaptors is discouraged since
in an overpressure condition the gauge could be forced out of the adaptor and thus constitute a safety
hazard. Additionally, the use of an elastomer seal is not recommended for high vacuum as outgassing
and/or permeation through the elastomer can cause errors in pressure measurement. A sensor with a KF
flange and elastomer O-ring seal is suitable only for pressure measurement down to 1x10
-7
Torr.
When inserting a nude sensor into a port, do not bend, damage, move the electrodes or feed-through
pins. Do not short the elements to one another, the chamber, or any components inside the chamber. If
there is any question of clearance for the electrode structure or of possible damage to the electrode
structure, it is recommended that the nude sensor be mounted in a nipple, (i.e. MKS p/n 100883069). The
MKS nipple includes a screen that helps to prevent ion coupling. This mounting is also recommended to
assure the nominal rated sensitivity.
7.2.6 Connecting a Hot Cathode Sensor to the 946 Controller
A sensor cable with a D-sub connector (Figure 7-1) for the module connections and molded plug for the
hot cathode sensor is required for operation.
Figure 7-1 Connector on the Back of the HC Module