Abstract: A movable piston is arranged within an open-ended cylinder, the piston having a peripheral groove for receiving liquid mercury to create a sliding gas-tight seal between the piston and the cylinder. The cylinder wall is provided with a plurality of openings, arranged to prevent mercury from escaping through said openings while permitting gas introduced into the interior of the cylinder to escape therefrom. When the piston reaches an equilibrium condition, the height of the piston represents the gas flow rate, which is determined by the flow rates through the total number of openings beneath the sliding seal. As an alternative embodiment, the flow rate is controlled by a downwardly moving piston. As another alternative embodiment, the piston is free to move up or down to compensate for fluctuations in pressure and/or flow rate within the cylinder.

Abstract: Measuring apparatus for calibrating flow meters and the like comprising a piston slidably mounted within piston cylinder means which receives gas passing through the flow meter being calibrated to cause the piston to be lifted. A precision encoder is rotated responsive to the movement of tape means aligned with the central axis of the piston and entrained about a pulley driving said encoder means. The tape is also connected to counterbalancing weight means for enhancing the sensitivity and accuracy of the measuring apparatus. The system electronics initiate operation of timer means upon the first pulse generated by the encoder means after operation of a start button and terminates the operation of the timer means upon the first encoder pulse generated after operation of stop button.Temperature and pressure in the piston cylinder are constantly monitored. These readings are employed at the time flow rate calculations are performed to correct the flow rate calculated to standard temperature and pressure.

Abstract: Control means for a welder of the "tungsten-inert-gas" type which senses even momentary engagement of the workpiece by the torch to initiate gas flow. The welding region is initially purged by the gas. After a predetermined timed interval the output of the welding power source is elevated to a level sufficient to cause the striking of an arc.Gas flow is maintained during the welding operation and for a predetermined time interval after extinction of the arc is detected.Means are also provided for visually indicating gas flow and further for automatically preventing the striking of an arc when gas flow is exhausted.Means are provided so that the welder power supply may also be turned on automatically to eliminate the need for foot or hand-operated switches conventionally used to turn on the welder power supply.Sensing means are also provided to protect the torch from becoming accidentally "welded" to the workpiece.