DE1008397B - Circuit for approximate measurement of the minimum value of a wave voltage, preferably the white level in television transmitters with negative modulation - Google Patents

Description

GERMAN

In the case of television transmitters with negative modulation, there is usually a certain minimum value that is broadcast High-frequency power prescribed as a so-called white value. For the practical operation of television transmitters it is necessary to continuously monitor the white level 5. It has been suggested to control of the white value with the help of an oscilloscope. But it has been shown that this is for practical operation is too imprecise. It is desirable to have the white value displayed continuously readable instrument, and besides, it is great for the practical operation of television transmitters Advantage if a warning is triggered when the target white level is not reached.

An arrangement for measuring the ripple of a ripple voltage is already known in which the Wave voltage is applied to a capacitor which is in series with a valve and is charged from the peak voltage of the wave voltage and the valve is stressed at the voltage minimum in the reverse direction with the differential voltage and over a second valve, a second capacitor is charged with this differential voltage, so that between this capacitor and the common negative pole the appropriate resistance through a voltage divider loaded sum of the mean value of the shaft voltage and the differential voltage occurs and a point is tapped by means of a zeroing instrument, which divides the voltage according to the ratio divides the differential voltage to the mean value of the shaft voltage.

It is also known to measure the voltage of a pulse train via switching elements blocking direct current is guided to measure by two rectifiers, so connected to the output of the pulse generator are connected that at the output of one of the rectifiers the positive, at that of the other the negative Parts of the pulses occur, and each charge a capacitor with these pulse parts, which can be used for display by addition.

Both circuit arrangements are not, however, for the display of the white value of a television transmitter suitable for an instrument.

The present invention relates to a circuit for the approximate measurement of the minimum value a wave voltage, preferably the white level in television transmitters with negative amplitude modulation.

According to the invention, the wave voltage, preferably the video voltage, is passed to a capacitor a rectifier with such polarity placed that the capacitor with increases in the wave voltage charged via the blocking resistor of the rectifier and when the shaft voltage is reduced Circuit for approximate measurement

of the minimum value

a shaft voltage,

preferably the white level

at television stations
with negative modulation

Applicant:
Siemens & Halske Aktiengesellschaft,

Berlin and Munich,
Munich 2, Witteisbacherplatz 4

Dipl.-Ing. Friedrich Kauderer, Berlin-Siemensstadt,
has been named as the inventor

is discharged through the forward resistance of the rectifier. The voltage across the capacitor is then a measure of the minimum value of the wave voltage, preferably the white level, and can optionally can be fed to an instrument for display via a DC amplifier.

In a further development of the invention, the capacitor voltage is used in a manner known per se a comparison voltage, preferably with one derived from the peak value of the high-frequency voltage Setpoint voltage, in particular in a tube bridge circuit known per se, compared and the resulting differential voltage for display in an instrument and / or for actuation of a relay is used, which generates an acoustic signal when a specified value of the differential voltage is exceeded and / or a visual warning display is triggered.

The invention is to be explained below with reference to the basic circuit of FIGS. 1 and 2:

In Fig. 1, the modulated high-frequency voltage taken from the television transmitter is fed to terminals 1 and 2. When the capacitor 4 is connected in parallel with the resistor 5, the directional conductor 3 forms the video voltage with suitable dimensioning, which in turn feeds the capacitor 7 via the directional conductor 6. Since the directional conductor 6 has the opposite polarity as the directional conductor 3, the voltage on the capacitor 7 follows the increases in the video voltage occurring at the parallel connection of capacitor 4 and resistor 5 via the blocking resistor from rectifier 6, ie very slowly, and decreases in the video voltage via the

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Forward resistance of directional conductor 6, ie very quickly. The voltage across the capacitor 7 is thus a measure of the white value and can optionally be displayed in an instrument via a direct current amplifier. The dimensioning of the resistor 5, the capacitor 7 and the blocking resistance of the rectifier 6 determine the speed with which the voltage on the capacitor 7 follows changes in the white value to higher values (in the direction of "gray").

In Fig. 2, the embodiment of Fig. 1 is expanded so that the resulting as a measure for the white value Capacitor voltage compared with a nominal value of the white \ vertes in a tube bridge circuit will. The same designations are chosen for the same switching elements as in FIG. 1. The voltage generated at the capacitor 7 is connected to the control grid as a direct current amplifier working amplifier tube 8 connected, in the anode circuit of the resistor 9 is located. To the Control grid of a second amplifier tube 10 connected as a direct current amplifier, the comparison voltage, e.g. B. one from the transmitter peak voltage Derived nominal voltage, supplied, which causes a voltage drop in the anode circuit at the anode resistor 11 caused. Between the anodes of the two amplifier tubes 8 and 10 is an instrument 12 for Display of the difference value and a relay 13 switched, which when a predetermined value is exceeded Value of the differential voltage triggers an acoustic and / or optical warning display.

Claims (3)

PATENT CLAIMS: 1. Circuit for approximate measurement of the minimum value of a wave voltage, preferably the white level in television transmitters with negative amplitude modulation, characterized in that that the wave voltage, preferably the video voltage, to a capacitor a rectifier with such polarity is placed that the capacitor when the Wave voltage charged via the blocking resistor of the rectifier and when downsizing the wave voltage is discharged through the forward resistance of the rectifier. 2. Circuit according to claim 1, characterized in that the capacitor voltage optionally an instrument for displaying the minimum value of the Wave voltage, preferably of the white level. 3. A circuit according to claim 1, characterized in that the capacitor voltage in itself in a known manner with a comparison voltage, preferably with the nominal value of the white value in television transmitters with negative amplitude modulation, in particular in a known per se Tube bridge circuit, is compared and that the resulting differential voltage for display is used in an instrument and / or to actuate a relay, which when exceeded a predetermined value of the differential voltage an acoustic and / or optical Warning display triggers. Considered publications:
German Patent Nos. 837 887, 868 185;
H ewe 1, Introduction to Television Practice, Berlin 1954, Verlag für Radio-, Foto- und Kinotechnik, p. 44, Fig. 54. 1 sheet of drawings © 70J 509/171 5.