| 摘要 |
PURPOSE:To enable the space between a cathode and a first grid to be accurately set automatically by using an A-E converter, which gives an electric signal corresponding to the space of a measured substance by converting the back-pressure of an air nozzle into the electric signal, comparing the electric signal sent from the A-E converter with a preset value, and obtaining a control signal corresponding to the result of the comparison. CONSTITUTION:Due to the back-pressure of an air nozzle 23, an A-E converter 24 produces an electric signal corresponding to a space formed between the nozzle 23 and the bottom surface of a recessed part 19 facing to the nozzle 23. Next, after the above electric signal is sent into a controller 26, the controller 26 detects the difference between the above electric signal and a preset value (X) by comparing them, and produces a control signal with direction adjusting the above difference to zero. Then, a pulse motor 28 receives the above control signal, rotates in direction corresponding to the above control signal, and makes the nozzle 23 to move along its axial line by means of a gear 29. Following that, when the space between a cathode (K) and the extreme end of the nozzle 23 is adjusted to the set value (X), a space (W) between the cathode (K) and a first grid (G) corresponds to a depth (V) of the recessed part 19 of a dummy 18, and the cathode (K) and the first grid (G) come to have a prearranged positional relationship. |
