Abstract: A ball testing device having a compact housing with a microphone for receiving the sound generated when a ball strikes a surface and generating output signals. An electrical circuit in said housing is configured to receive the output signals and process the signals to determine the time lapse between the first and second and the second and third successive bounces of the ball and provide the ratio of time lapse between the second and third bounces to that of the time lapse between the first and the second bounce to provide the coefficient of restitution of the ball. Said housing including a display for displaying the coefficient of restitution.

Abstract: There is described a vacuum gauge in which an anode grid defines an ionization volume directly into which electrons are injected where they collide with gas molecules and atoms to form ions. A collector electrode is mounted within the ionization volume.

Abstract: There is described a vacuum gauge in which an anode grid defines an ionization volume directly into which electrons are injected where they collide with gas molecules and atoms to form ions. A collector electrode is mounted within the ionization volume.

Abstract: The operating range of an ionization tube vacuum gauge is increased by applying at least two different bias voltages to the tube and measuring ion current for the two bias voltages. The ratio of the ion currents indicates vacuum pressure in the range of 10.sup.-1 to above 2 Torr. An ionization tube vacuum gauge provides a pressure read-out by the linear ion current response of an ionization tube between 10.sup.-10 Torr and 10.sup.-2 Torr. The non-linearity of the ion current response between 10.sup.-2 Torr and 10.sup.-1 Torr is compensated by a non-linear amplifier. Above 10.sup.-1 Torr the ratio of ion currents is utilized for determining pressure.