MKS HPS 937A Series, Руководство по эксплуатации и техническому обслуживанию владельца

Страница: 65 / 108

57
937A Multi-Sensor System
If a cold cathode sensor has been disabled using the XCCn command, the
ECCn command must be used to re-enable the sensor. No other method can
override the XCCn command. In the event that the cold cathode can not be
re-enabled from the Communications Module, the power switch on the Series
937A controller must be turned off (for at least 5 seconds) and then turned on
again. This will clear the disable condition from the Communications Module.
Using Protection and Control Set Points
The Series 937A controller has two pressure-based methods, protection and
control set points, to automatically turn off a cold cathode sensor's high
voltage in the upper portion of the operating range.
In the first method, if the pressure measured by a cold cathode sensor rises
above a protection set point
, the sensor will turn itself off. PRO appears on
the display in Pressure mode. The user must use one of the methods from
the previous sections to turn the cold cathode sensor off, and then back on.
In the second method, a sensor other than a cold cathode sensor may be
designated as a control sensor. If the control sensor's pressure reading rises
above the control set point, the cold cathode sensor will turn off. C T L
appears on the display in
Pressure mode. When the pressure falls below the
control set point, the cold cathode sensor automatically turns on again.
The control set point will only turn on the cold cathode sensor as the pressure
falls below the set point value, if it was first turn off by the control set point. The
control set point can not turn on the cold cathode sensor if it was turn off for
another reason. This includes the off state when the 937A is initially turned on.
Therefore, after power up the cold cathode must be turned on by one of the
methods previously mentioned before the control set point will function.
To use a control set point, a cold cathode sensor must be in Slot CC or A. Its
control sensor must be installed in either channel of Slot B, selected by the
DIP switch setting on the Analog Module.
Sensors that can be used as a control sensor are the Pirani,Convection
Pirani,and thermocouple sensors. In addition, the 1, 10, and 100 Torr
capacitance manometer heads may be used as control sensors. If there is
no control sensor installed, no control set point will be available.
If a Pirani,Convection Pirani or thermocouple sensor is used as a control
sensor, and it is disconnected or fails, the controlled cold cathode sensor will
be turned off just as if the control sensor's pressure reading had exceeded
the control set point.
For a control sensor to properly control a cold cathode sensor,
both sensors should be sensing roughly the same system
pressure.
If the system gas is not air/nitrogen, the cold cathode
sensor and the control sensor may not agree near the control set
point, since both sensors are gas dependent.