JPH03206934A - Hot cathode ionization vacuum gauge - Google Patents

Abstract

PURPOSE:To prevent blow-out of a filament by feeding electricity to the filament through a conductive material which is easier to be blown out than the filament. CONSTITUTION:When electricity is supplied to a filament 1 through current introducing terminals 1a, 1d, the current runs in a route along 1a-1-1d. Therefore, if a sudden rise of the pressure is brought about in this state of use, 1f is blown out, so that the filament 1 can be protected. Subsequent to the above case, current introducing terminals 1c and 1b are used to supply electricity. At this time, the current flows in a route along 1c-1e-1-1b. When the pressure is suddenly raised in this state, 1e is blown out, thereby protecting the filament 1.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a hot cathode! This relates to the sensor head of a vacuum gauge.

[Summary of the invention]

The present invention solves the problem of the filament burning out in hot cathode itjit vacuum gauges by applying electricity to the filament through a conductive material that is designed to burn out before the filament, thereby preventing the filament itself from burning out. This is what I did.

[Conventional technology]

Hot cathode ionization vacuum gauges have a problem in that the filament is heated by electricity when measuring pressure, so when the density of active molecules such as oxygen increases, the filament reacts with it and burns out. In order to solve this problem, a filament protection circuit is provided in which an electronic circuit detects when the pressure exceeds a set value and immediately stops heating the filament.

However, when a severe pressure increase occurs due to an abnormality or incorrect operation of the vacuum equipment system, it is inevitable that the filament will burn out before the filament protection circuit works. Some models have a spare filament to maintain the function of the sensor head even if the filament burns out, but in any case, after the filament attached to the sensor head burns out, the Ila
In order to revive Noh, the filament itself had to be replaced with a new one.

[Problems to be Solved by the Invention] As described above, in the conventional technology, the filament burns out when a sudden pressure rise occurs due to abnormality or incorrect operation of the vacuum device system. However, when replacing the filament itself, there were the following problems. (1) Filaments are usually treated to obtain the necessary thermoelectrons at the lowest possible temperature (for example, thoria coating), and are generally expensive due to the materials used. (2) If the filament is replaced, the temperature of the filament to obtain the necessary thermoelectrons may change, and the positional relationship with other electrodes may be slightly different, making it necessary to recalibrate. (3) If the sensor head is structured in such a way that other electrodes must be removed when replacing the filament, the replacement process itself is difficult. [Means for Solving the Problems] In order to solve these problems regarding the sensor head of a hot cathode vacuum gauge, the present invention is designed to connect the filament with a conductive material that is more easily burnt out than the filament. be.

In other words, in the sensor head of a conventional hot cathode ionization vacuum gauge, both ends of the filament are connected as shown in Figure 3. As shown in FIG. 4, the filament was directly connected to the current introduction terminal, but in the present invention, a conductive material that is easier to burn out than the filament is inserted between the filament and the 1t current introduction terminal.

Conductive materials that are more likely to burn out than filaments include wires and ribbons that have a smaller cross-sectional area than the filament if they are made of the same material as the filament, and conductive materials that react with the filament like oxygen if they are made of a different material than the filament. Suitable materials are those whose affinity for the gas that can lead to filament burnout is greater than the affinity between the material used for the filament and the gas. [Function] When the sensor hand of the hot cathode t-separation vacuum gauge according to the present invention is used, if a sudden pressure increase that cannot be followed by the filament protection circuit occurs due to an abnormality or erroneous operation of the vacuum 4-IT system, the filament and current Since the conductive material between the lead-in terminals is immediately burned out and the current to the filament is cut off, the filament itself is not burned out.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of the present invention for a BA gauge type sensor head, and FIG. 2 shows an embodiment of the present invention for a hemispherical type sensor head having a shield electrode on the outside of the filament. (
The hot cathode), la, 1b, lc, and ld are terminals for introducing current into the filament, and Is and If are conductive materials that are more easily burned out than the filament. Initially, when electricity is applied to the filament using current introduction terminals 1a and 1d, the current is 1a - 1
- 1 f - 1 d (7) Root Tony? at'l
Le.

Therefore, if a sudden pressure rise occurs during use under such conditions, 1f will burn out and protect the filament 1.

When this situation is reached, the next step is to connect the current introduction terminals lc and l.
energize using b.

Then, the current flows through the route 1 c-1 e-1-1 b.

Therefore, if a sudden pressure increase occurs during use under such conditions, le will burn out and the filament 1 will be protected.

You can connect the conductive material, which is easier to burn out than the filament, to only one end of the filament, but if you connect it to both ends of the filament as shown in Figures 1 and 2, it will work even if there are no two filaments. Up to two abnormal situations can be handled without breaking the vacuum of the vacuum device. Also, if you want to restore the function of the sensor hand after both is and if are burnt out, you will need to replace le and 1f, but unlike filament, there is a certain degree of freedom in where le and ifO are installed, so Replacement will be easier if it is located in a location where it can be easily replaced.

In particular, in the case of the sensor head having the structure shown in Fig. 4, if the filament itself burns out as in the conventional case, the filament could not be replaced without removing the shield electrode, but in this embodiment, le, If There is no need to remove the shield electrode, and the function of the sensor head can be restored very easily. [Effects of the Invention] As explained above, the hot negative ionization vacuum gauge according to the present invention has the advantage that even if a sudden pressure increase occurs due to an abnormality or erroneous operation of the vacuum device system, the conductive ionization vacuum gauge connected in series with the filament Since the filament itself is prevented from burning out by burning out the material first, it has many advantages as described below.

(1) Since the conductive material used to protect the filament can be set at a lower cost than the filament, the cost of restoring the function of the sensor head is reduced. (2) The conductive material for protecting the filament can be placed in a position that is easy to work with, making it easier to restore the function of the sensor head. (3) Since the filament remains as it is when the function of the sensor head is regenerated, there is almost no change in sensitivity before and after the function is regenerated.

(4) In the case of a sensor head with a structure in which there is another electrode (for example, a rolled electrode) on the outside of the filament, the function can be restored without removing the electrode on the outside of the filament, so sensitivity changes can be suppressed and The effect on ease of performing function regeneration work and cost reduction will be greater.

[Brief explanation of drawings]

Fig. 1 shows an embodiment of the present invention for a BA gauge type sensor head, Fig. 2 shows an embodiment of the present invention for a hemispherical type sensor head, Fig. 3 shows a conventional BA gauge type sensor head, and Fig. 4 shows an embodiment of the present invention for a BA gauge type sensor head. is a conventional hemispherical type sensor head. Filament (thermal cathode) lb, lc, ld... Terminal for introducing children's current into the filament 1e. 1f... Conductive material for filament protection 2 ・ ・
・Grinode (anode) 3...Collector (ion collecting electrode) 4...Shield t pole or higher

Claims (1)

[Claims] A hot cathode ionization vacuum gauge characterized by applying electricity to the filament through a conductive material that burns out before the filament.