INSTRUMENT FOR MEASURING DEGREE OF VACUUM OF CRT

Japanese Patent JPS63188732

A

PURPOSE:To measure the degree of vacuum of a flat matrix CRT with high accuracy by providing a power source which supplies an electron flow to between the cathode electrode and other electrodes of the flat matrix CRT and a current detector which measures the ion current. CONSTITUTION:When the cathode electrode 1c is heated by an AC power source 1g first, thermoelectrons are emitted by the electrode 1c and reach a grid electrode 1b which is applied with a positive potential. Some of the thermoelectrons reaching the side of the electrode 1b pass through the grid electrode 1b and when they approach an anode electrode 1a, they are pushed back by the negative potential of the electrode 1a to advance spirally toward the electrode 1b and strike on remaining gas molecules in the middle to generate electrons. The ions have positive electrons, so they are attracted to the electrode 1a and a current corresponding to the quantity of generated ions flows to the electrode 1a. The value of this ion current is larger as more gas molecules remain, i.e. at the low degree of vacuum. For the purpose, the degree of vacuum obtained for the current value is displayed previously on an ammeter 1d and the degree of vacuum of the CRT 1 is measured directly with high accuracy.

NAKANO TAKAO
IWATA SHUJI
KOITABASHI MASAYASU

JP2072087A

August 04, 1988

January 30, 1987

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MITSUBISHI ELECTRIC CORP

G01L21/32; (IPC1-7): G01L21/32

Masuo Oiwa

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