SU403112A1 - DEVICE FOR MEASURING TEST TELEVISION SIGNALS - Google Patents

Description

one

The invention relates to the field of television measurements and can be used to measure a portion of a test signal, for example, a reference interval with a reference level.

A device for measuring television sigals is known, which contains at its output an execution unit, for example, a recorder controlled by a pilot of a pulse of the interval of a control signal, the inputs of which are measured signals.

In order to improve the measurement accuracy, the charging capacitor is connected between the inputs of the device and the execution unit, and a filter plug is connected directly to the input of the execution unit, the input of which is controlled by a switch controlled by the driver of the interval of the pilot signal interval.

FIG. 1 shows a block diagram of the proposed device; in fig. 2 - plots showing his work.

At the input of the proposed device, the level-fixing circuit 1 of the measured pilot signal and the driver 2 of the pilot-signal interval pulse are connected in parallel, the outputs of which are connected to the signal input and the start input of the execution unit 3, respectively. 11, lock

Level 1 is made in the form of a series-connected charging capacitor 4, a filter plug 5, a normally closed controlled switch 6 and a voltage source 7

fixing. B. turn key 6 is connected

with shaper 2 output. General point

the capacitor 4 and the filter 5 is the output

level 1 locking chains.

The proposed device works as follows.

The variable cohort signal 8 of the full signal 9 (Fig. 2) is fed from the output of the source of the latter to the paralleled inputs of the level detection circuit of the measured pilot signal 1 and the driver 2 of the pilot interval pulse, which forms the pulse 10 with the time position corresponding to the temporal position of the measured control signal

in full television signal. This impulse causes the synchronous locking of the normally closed control key 6, as well as the start of the execution unit 3.

Upon entering the input of fixing circuit 1, the full television signal is attenuated by a divider consisting of an internal resistance of the signal source, a charging capacitor 4, a filter plug 5 and a normally closed circuit.

key 6.

In this case, the signal attenuation is equal to the ratio of the total resistance of the signal source and the charge capacitor 4 (upper divider arm) to the total resistance of the filter plug 5 and the normally closed switch 6 (lower divider arm).

The filter plug 5, which has a galvanic connection between the terminals, frequency selects the signal components, preventing the signal from closing to the key, for example, the chromaticity region, i.e., their attenuation by a divider. For components that are not included in this equipment, including components that determine the signal level (in the case of a television signal, this is the medium frequency range of 8-30 kHz), the filter is a small resistance compared to the upper arm of the divider. .

Thus, for these components, the signal attenuation is equal to the ratio of the total resistance of the signal source and the charge capacitor to the residual resistance of the normally closed controlled key.

Before the occurrence of the measured control (signal) of the south signal 8, the pulse 10 of the driver 2 lowers the key b by the transmission time of the control signal, and the resistance of the key increases sharply and the divider is broken. The control signal 11 (Fig. 2), separated from the full signal, is fed to the signal input of the execution unit 3. For an undistorted transmission of the measured signal to the input of the power block, the input resistance of the latter and also the resistance of the open key must be large compared to the total resistance of the upper Ilecha divider. The same pulse of the driver starts the execution unit, and the pilot signal is synchronously processed.

When the key is closed, the signal recharges the capacitor 4 with a constant time equal to the product of the internal resistance of the signal source and the capacitance of the capacitor. After any change in the signal after a few constant times, the recharging of the capacitor practically stops.

All tell-tales are separated from pre-existing signals by a fixation interval — a reference level pad corresponding to the black level of their drivers.

This level and the presence of inaccuracies of fixation in the sensors of control signals and their input devices may not correspond to the level of a black full television signal.

The key is unlocked within the readout level site after several constant times since the start of the site transfer. At the same time, for each key opening, the capacitor 4 is charged to the level of the reading pad. After opening the key, due to the large response of the signal input of the executive unit and the open key, the charge of the capacitor is not

varies, and the sum of the voltages of the signal reading area and the accumulated potential at the capacitor is equal to the clamping voltage.

Therefore, the control signal transmitted relative to the reference area arrives at the executive unit always relative to the clamping voltage and, therefore, with the fixed level of the reference area. Upon completion of the pilot signal transmission, the driver pulse is terminated, the key is closed, and the subsequent signal is suppressed.

Thus, as a result of the absence of a measurable signal, the key is closed, but it is not the occurrence of this signal during the sampling site that it opens with a pulse of the driver for the transmission time of the measured signal; the latter is allocated, fixed at the level of its reference site, and fed to the executive unit.

The greater the suppression of a signal by a normally closed switch, the less constant the recharging time of the capacitor, the greater the input resistance of the execution unit and the resistance of the open key, the longer the pause between the end of the last signal and the beginning of the key, and the faster the opening process is, the more accurate fixing the level of the control signal and more accurate measurement.

In this way, the meter parameters are selected.

Due to the high impedance of the filter filter at the frequencies of the chrominance signals, these signals do not affect the nonresarer of the capacitor 4. The capacitor recharges through the galvanic connection between the filter terminals only with a luminous signal, as a result of which the control signal level relative to the chrominance region is prevented. If the meter is used only for black and white TV signals, the filter plug may be removed from the device. In this case, the capacitor 4 is connected directly to the key 6.

Since the level of the measured control signal is fixed at the input of the execution unit relative to the reading pad preceding the directly measured signal, errors caused by inaccuracy of fixation of the control signals in the sensors and input devices, and this increases the measurement accuracy.

In addition, the traditional level fixing circuit of the full signal and the generator of horizontal fixing pulses for controlling them are absent in the level fixing circuit of the meter. This simplification is achieved by combining level fixation and separation of the measured signal from the full signal.

Separating the measured signals transmitted with a high duty cycle from the full signal allows you not to keep the constant component of the signal at the input of the execution unit, the circuit of which is also simplified, since the processing circuit of television signals without restoring the constant component (without electroplating between the cascades) is better than the circuit with the transmission of the constant component of the television signals.

Subject invention

A device for measuring test television signals containing, at the output, an executive unit controlled by a pulse generator of a pilot signal interval, ia whose inputs are given measured signals, characterized in that, in order to improve measurement accuracy, between the inputs of the device for measuring test television signals and executive of the block, the charge capacitor is turned on, and a filter plug is connected directly to the input of the execution unit, to the input of which, through a driver controlled the pilot interval pulse key is energized from the source of the fixation reference level.

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