2.1 General Description The Series 340 Vacuum Gauge Controller (VGC) measures pressures from less than 1 x 10 -9 Torr (1.3 x 10-9 mbar or 1.3 x 10-7 pascal) to atmosphere by use of a single ionization gauge and two Convectron Gauges. Pressure readout is via a front panel display and analog outputs. Resistance heating degas is standard. An interlock is provided to allow degas only when the ion gauge tube is ON and the displayed pressure is below 5 x 10-5 Torr. Pressure reading during degas is not possible. The 340 VGC is a modular instrument with infrequently used controls housed behind a hinged front panel, thus reducing front panel clutter and allowing the VGC to reside in a half-rack space. 2.1.1 Available Options 2.1.1.1 Remote Input/Output The 340 VGC can be ordered with a factory installed remote I/O option which provides an ion gauge (IG) status relay, remote gauge on/off input and remote degas on/off input functions. 2.1.1.2 Process Control Relays The 340 VGC can be ordered with a factory installed process relay option which provides automatic ion gauge turn-ON from Convectron channel "1" and a Convectron Gauge process relay output that is user selectable to operate from channel "1" or "2". 2.1.1.3 Ion Gauge Cables The VGC is capable of operating an ion gauge located up to 50 feet away from the controller by using standard cables. Degas power delivered to the gauge decreases with cable length. Cables are available for use with glass or nude Bayard Alpert (B-A) gauges. 2.1.2 Mounting Options The 340 VGC can be ordered with a variety of mounting options to fit your needs. This includes half rack (standard), full rack, or bench mounting. See Figure 3-2 on page 20 for dimensional illustrations.