4 Operation
32
Series 340 Vacuum Gauge Controller
Instruction Manual - 340005 - Rev. D
4.1.1 Sensor Failure
If the gauge tube becomes disconnected from the controller or if the sensor wire in the gauge tube
fails, the controller will indicate 9.9E+9. If the tube is unplugged for a powered controller, there
may be an instantaneous (0 to 0.2 seconds) drop in the pressure indication and the process control
relay could activate for this brief time, depending on the order in which the tube pins break contact.
4.1.2 Power ON/OFF
To turn ON the 340 VGC, depress the top half of the power switch located on the rear panel. To
turn OFF the VGC, depress the lower half of the power switch.
NOTE: There is NO power switch for the Convectron gauge.
When the VGC is turned ON the Convectron gauges are ON.
4.1.3 Electrometer Module Units of Measure
The Units of Measure Display is selectable via a switch on the Electrometer Module. These units are
indicated on the front panel label when shipped from the factory.
Refer to Section 5.2 on page 45 for information on changing the units of measure for the Ion gauge;
Section 6.2 on page 51 for information on changing the units of measure for the Convectron gauge.
The pressure units label can be changed by the user if the system of units is changed. Slip the label
card out of the top of the front panel and insert the appropriate pressure units label.
4.1.4 Ion Gauge ON/OFF
The ionization gauge can be turned ON or OFF with the front panel momentary rocker switch or by
remote control.
To turn ON the ion gauge from the front panel, press the momentary rocker switch (see Figure 4-1).
To turn it OFF, press the switch again. The digital display on the front panel will illuminate when
ON. The display will initially display 9.9+9. After an approximately 2 seconds, the actual pressure
will be displayed.
NOTE: The maximum voltage appearing on the gauge tube contacts will be
5.5 Vdc when the ion gauge is OFF.
4.1.5 Degas ON/OFF
The I
2
R degas can be turned ON or OFF by the front panel momentary rocker switch (Figure 4-1) or
the remote control input. To turn degas ON, press the DEGAS momentary rocker switch. An LED on
the front panel illuminates when degas is ON. To turn it OFF, press the rocker switch again or press
the GAUGE momentary rocker switch to turn OFF degas and turn ON the gauge.
Degas cannot be activated unless the gauge is first turned ON and indicated system pressure is
below 5 x 10
-5
Torr. This prevents degas turn-on at pressures that are too high for the gauge
materials, or where degas is of no practical use. Pressure measurement is not possible during degas.
NOTE: During degas, the digital display is OFF.
4.1.6 Remote Input/Output
Two TTL compatible inputs are provided through the rear panel allowing control of the ion gauge
and degas. The function of the front panel keys is reproduced by either a contact closure or an
asserted low (0V) logic state on these inputs. This low state must be held continuously for at least 25
milliseconds. After this, the input must be allowed to pull high for at least 105 milliseconds before
another low will be accepted. These inputs have passive pull-ups.
