Abstract: Test gas passing through leaks is conducted through a conduit to the discharge end of a counterflow pump or turbo-molecular pump. The leak gases advance opposite to the pumping direction of the counterflow pump to its intake side, and is detected by a detector connected to its inlet. The heavier gases (air) interfering with the detection, for which the counterflow pump has a substantially higher compression ratio, however, are retained mostly by the detector. Heretofore, the partial pressure of the test gas in the detector or the signal given off by it were used as a measure for the test gas current passing through a leak, while according to the invention the speed of the counterflow pump is varied so long until the detector signal has a predetermined size. The invention includes a device for adjusting the speed of the counterflow pump so as to obtain a high detection accuracy at less cost than heretofore.

Abstract: A leak detector for detecting the presence of a leak in a vacuum vessel exposed on its exterior to a test gas, comprising, a turbo vacuum pump having an inlet connected to a gas sensor for sensing the presence of a test gas and an outlet, a forepump connected to the outlet for receiving gas from the outlet and an intermediate inlet in the turbo vacuum pump connected to the test vessel. When test gas is supplied to the intermediate inlet from the test vessel, indicative of a leak, the test gas flows in counter-current flow to the operating direction of the turbo vacuum pump, to the gas detector, where the test gas is detected.

Abstract: The self-calibrating leak detector circuit arrangement comprises a measuring probe for generating an electrical signal when exposed to the leaking gas. A measuring amplifier is connected to the probe for amplifying the electrical signal and a second integrating amplifier stage is connected to the measuring amplifier output for amplifying the signal. The second amplifier stage has a feedback connection to the input of the measuring amplifier for counteracting at least a part of the electrical signal from the probe. A push button switch is advantageously connected between the measuring amplifier and the second amplifier stage to momentarily impress the output of the measuring amplifier on the input of the second integrating amplifier stage. Indicators are connected to the outputs of the respective amplifiers for a reading of their respective outputs.