CS201241B1 - Connection for measuring the thermic emission of the tube grid - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention

The electron tube, in particular the power tube, emits electrons from its surface under load at rated power and at a hot cathode, its current being dependent on the temperature of the grid, its emission capability and the magnitude of the output potential. This phenomenon, called the thermal emission of the grid, must be measured.

In the prior art apparatus for measuring thermal emission from the surface of the transmission electron grids, a periodic broadband voltage is supplied to the grating from a power source when the cathode is heated. In operation of the tube, in addition to the cathode heat radiation, its tube is also heated by its own power dissipation due to the positive half-period of the rectified excitation voltage applied to the tube. When there is a negative half-period of the excitation voltage on the grid, the current emitted from the grid surface flows to the cathode and its size is measured *

Using this known device for measuring the thermal emission of power tube grids for broadcasting and industrial equipment, there is a considerable demand for a source that must be designed and constructed with respect to both a high negative potential where the current emitted by the grid is in a saturated region and secondly, with respect to the power required to achieve maximum grid loss. Because it's basically about

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201 241 of a single-phase one-way rectifier, a direct current flows through the secondary winding, which increases the magnetic induction in the transformer core and thus increases the losses in the iron. The transformer is structurally large and costly for the required power. Its resulting efficiency is low, which has an adverse effect on power consumption and uneven load on the power supply network.

With the new types of transducer tubes intended for use in the high and very high frequency range, the current measurement device cannot be used, since the permissible grid loss is already achieved at a voltage several times lower than the negative half-wave voltage required to measure the thermal emission current in the saturated region. In addition, there is an unfavorable delay between the individual half-periods of the positive voltage at which the grid cools and the thermal emission current decreases, causing a major measurement error.

These disadvantages are eliminated by the connection of the device for measuring the thermal emission of the vacuum tube grid according to the invention, which consists of a power supply whose input terminals are connected in parallel to the control circuit and to the negative pulse source, the first control circuit output being connected to and the second output of the control circuit is connected to a proximity switch, to which is also connected one output of the negative pulse source, the other output of which is connected to an evaluation circuit that is grounded, and the output of the proximity switch is connected to the output terminal of the the output of the power supply is connected in parallel via the indicating device.

The advantages of connecting the device according to the invention are that the measurement does not cause DC saturation of the transformer core, reduces energy losses and eliminates unbalanced load on the supply network. The measurement of the thermal emission of the lattice is performed immediately after the positive voltage on the grid has disappeared in a short period of time during which the grid does not cool and the measured value corresponds to the maximum value of the thermal emission current in the saturated region. The magnitude of the negative pulse voltage is not dependent on the voltage, which is the loaded grid, and therefore all types of power tubes can be measured using this device.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be explained in more detail with reference to the accompanying drawings, in which FIG. 1 illustrates prior art thermal emission measurement devices from a tube grating surface; FIG. voltage + Ua -Ug on the grid as a function of time.

In the prior art device for measuring the thermal emission of a tube grid, see Fig. 1, the function is followed by the voltage from the power transformer TR is applied to a one-step controlled rectifier RU. The positive half-wave of the rectified voltage is applied to the grid of the measured tubes and it is loaded by the power dissipation, the magnitude of which is measured by a voltmeter M1 with a series diode D1 in series and an ammeter M2. The thermal emission current of the grid is measured by M3 when the negative diode D2 is applied to the grid by the second diode D2.

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The connection of the device for measuring the thermal emission of the vacuum tube grid according to the invention, Fig. 3, consists of a power source VZ. whose two input terminals 1 β 2 are connected in parallel to the control circuit RO and to the source of negative pulses ZZI. The first output of the control circuit SO is connected to the negative pulse source ZZI and the second output of the control circuit RO is connected to the contactless switch BS. to whose second input the output of the negative impulse source ZZI is connected. The second output of the ZZI negative pulse source is connected to the VO evaluation circuit. which is grounded. The output of the contactless switch BS is connected to the output terminal J, to which the power supply VZ and the indicating device IP are connected in series. The output terminal 2 of the tube emission thermic emission measuring device is connected to the tube 6 of the electrode E with anode A and an earthed cathode K.

How power source VZ. thus the IP indicating device is grounded.

The punkoe wiring of the tube emission measurement device E is as follows:

The mains voltage is applied to terminals 2 and 2 of the VZ power supply, which can be connected as a two-phase bridge with a thyristor connected in series with the load being measured by the E tube. E. The power supplied by the VZ power supply is indicated by the IP indicator. When there is zero voltage on the grid G, the positive voltage of the power supply VZ goes through zero, pulses are generated in the control circuit RO, which control the negative pulse source ZZI and the contactless switch circuit BS, The contactless switch BS becomes conductive and are fed to the grid 5 at a time interval that is defined by the end of the switching-off time of the power thyristor of the power supply VZ at commutation and when the power thyristor is able to remain in the closed state. The maximum current flowing at the moment of a negative pulse between the grating G and the cathode K of the measured electron E is evaluated in the evaluation circuit VO. The voltage curve + Ug and -Ug on the grid G is shown in Fig. 3.

The connection of the vacuum emission measuring device is used in the manufacture and measurement of power tubes for transmitters and for various industrial applications.

Claims (1)

Circuit diagram for measuring the thermal emission of a vacuum tube grid, characterized in that it consists of a power supply (VZ) whose input terminals (1, 2) are connected in parallel to the control circuit (RO) and to the negative pulse source (ZZI). circuit (RO) is connected to the negative pulse source (ZZI) and the second output of the control circuit (RO) is connected to a contactless switch (BS) to which is also connected one output of the negative pulse source (ZZI), whose second output is connected to the evaluation circuit (VO), which is grounded, while the output of the proximity switch (BS) is connected to the output terminal (3), to which the power supply output (VZ) is connected in parallel via the indicator (IP).