MKS 937B - Page 40

MKS 937B Operation Manual
40
The Protect Setpoint function will turn the cold cathode high voltage off at the specified
pressure readings. The valid Protect Setpoint range for a cold cathode is 1.0x10
-5
torr to
1.0x10
-2
torr. The default value is 5.0x10
-3
torr. It is enabled at all times in the 937B.
When the Protect Setpoint is triggered, the Auto control is disabled. The gauge
can then be turned on only manually or by serial command. This is due to the fact that
the gauge control setpoint should normally act first. When Protect Setpoint is tripped,
this indicates that the control setpoint is not function properly, probably due to an
inappropriate system configuration (control gauge and ion gauges are not connected
to a same volume), or to a control gauge malfunction.
6. Relay
Relays for each channel are preset as shown below. These values are auto-detected. When
single sensor CC board is used, 4 relays are assigned to each cold cathode sensor.
Sensor location A1 B1 C1
Relay assigned 1 & 2 & 3 & 4 5 & 6 & 7 & 8 9 &10 & 11 & 12
7. Enable
There are three ways to set a relay:
 SET: forces the relay to stay in the activated state (closed) regardless of pressure
and setpoint values
 CLEAR: forces the relay to stay in the deactivated state (open) regardless of
pressure and setpoint values.
 ENABLE: the relay status is determined by the pressure, setpoint value, and
direction.
8. DIR
To prevent the cold cathode from being turned on at high pressure, the DIR for a cold
cathode is set to BELOW permanently.
Refer Figure 8-1 for more detailed description of the direction setting.
9. SET SP
This function permits input of a desired setpoint value. The valid range is 2x10
-10
to 5x10
-3
torr. To speed up the value change, hold the
or key.
10. Hyst
Once a setpoint value has been changed, the hysteresis value will automatically be changed.
Since the direction is set to BELOW for cold cathode sensor only, the hysteresis will be set to
1.5xSetpoint automatically.
To modify the hysteresis, move the cursor to the hysteresis value and press
Enter
. Use the
or
key to change the value, then press
Enter
again to set the value. The minimum
hysteresis value for a cold cathode gauge is 1.1xSetpoint; DIR is set to BELOW at all times.
11. Control SP
The Control Setpoint function is used to turn the cold cathode gauge on or off by using a
reference gauge, typically a Pirani or Convention Pirani. This function prevents the cold