Model FH-1 Gauge Head

The filament-grid and grid-collector distances on the Model FH-1 Gauge Head are small, permitting good linearity up to high pressures. The open "fly-through" structure does not perturb molecular beams by scattering due to pressure build up, and allows beam detection even at large distances from the nozzle with good signal-to-noise ratio. Except for the power supplies and meters, all the circuit components are mounted on the gauge in order to give the very fast response. The low power dissipation operational amplifier is easily replaceable; other components are epoxied into the body of the gauge. Additional amplifiers are provided. The filament is user replaceable and a spare filament is supplied with each unit. Two screw holes are available for mounting the gauge.

Feedthrough and Cables

The cable between the control unit and vacuum feedthrough is four meters long. A two meter length of cable fitted with a connector for the gauge head is also supplied. This cable can be shortened by the user for connecting to the vacuum side of the feedthrough. The feedthrough has eight pins and an outside diameter of 1.25". A vacuum flange is not supplied as standard equipment-the feedthrough can be soldered by the user into a flange or an 0-ring seal can be made, using a schematic diagram included in the operating instructions manual. An 0-ring is provided.