SU30326A1 - Apparatus for measuring the highest and average amplitude values of a modulated high frequency voltage or current - Google Patents

Description

The task of determining the coefficient of the V 1 /. max - mm bin of modulation K dits to find - the average amplitude of the voltage or current of high frequency and min the maximum swing of the acoustic component. Some of the methods for determining K are based on measuring the constant and effective value of the variable components of the rectified high frequency current. The value found to go to the amplitude values is multiplied by y 2; this is legal only in the case of purely sinusoidal changes in amplitudes and may, generally speaking, be the source of errors. Methods are known that make it possible to find - min, however, not by not mediocre readings on the instrument, but only with the help of more or less painstaking manipulations. In many cases, it is limited to finding one 240 calculus to, as is the value of: V -U max cf. In this case, obviously, there must be a guarantee of symmetry of modulation with respect to the received (measured) Fgp value. The latter value is sometimes calculated by the formula: V -4-V, f max I mm Here also lies the premise of modulation symmetry, which sometimes may not be true, because the nature of the changes and amplitudes depend on the one hand on the form of the acting force, and on the other - from the design of the transmitting device as a whole. Therefore, from the method of determination it is necessary, generally speaking, to require the possibility of obtaining both the magnitude of the average amplitude of the high frequency and the maximum value of the asymmetry.

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With the current state of the art of transmitting amplifying devices, there is no reason to fear significant deviations of modulation from symmetry. In this case (with symmetric modulation), the measuring circuit can be significantly simplified (Fig. 4).

Two pargiln circuits are connected to the communication circuit: one consisting of rectifier 2, connected in series with resistance 3 and a current detecting device 4, and the second from rectifier 5 and a capacitor 6 shunted by leak 7, in which VK | Another measuring device 5 is used. Device 4 indicates the average value of the rectified power of a high frequency or a value proportional to it V „. The readings of instrument 8 are proportional to the voltage at the terminals of the capacitor 6 or, alternatively, at the same.

Modulation depth ratio

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To 100%

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determined from the readings of both instruments.

With appropriate calibration of both devices, in the case of installing the arrow of a voltmeter 5 per 100 divisions, by exceeding the reading of a voltmeter 8 above this figure, the value K can be obtained directly.

Use instead of two separate, unrelated 4 8 devices, their combination according to the Ferrie principle or any of the devices that indicate the ratio of currents in the same way as described for the case of asymmetric mode. It is possible to carry out the index 10 of the modulation depth (with a direct reading of the coefficient K), whose readings will not depend, within certain practical limits both on the magnitude of communication with the transmitter, and on changes in the latter's mode of operation (phyL 5).

It is possible, instead of devices 4 and 8, to take one microammeter 9 (fig. 6) and to include it in this or that circuit. When it is switched on parallel to its corresponding shunt sensitivity / 2, measurement V is performed. After switching the movable system of device 9 in series with resistance 7, we obtain the value of Axxconstructively, the device can be carried out in such a way that the arrow comes to the first (zero) division only under the action of voltage accepted for normal value. Subsequent divisions are applied in hundredths of the normal voltage or, equivalently, as a percentage of the modulation depth.

If there is no modulation, the arrow will indicate zero when the instrument is turned on in any of the circuits.

With modulation, the voltage in circuit 5, 6, 7 will increase by an amount proportional to K, and will remain unchanged in circuit 2, 3, 4. This is the basis for the possibility of bringing the device to the correct initial value of Y, p during operation of the transmitter and subsequent then a direct reading on the instrument of the desired modulation depth coefficient K. In FIG. 7, 8 depict the diagrams of the devices described when using two-anode kenotrons.

The subject matter of the invention.

1. Device for measuring the highest and average amplitudes of the high-frequency modulated voltage or current, characterized by the use of circuits connected to the source of modulated current with three rectifiers 4, 9, 11, included as follows (Fig. 1): rectifier 4 connected in series with a capacitance .5 shunted by resistance 3, the second rectifier 9 is connected together with capacitance 8 parallel to resistor 3, and the third rectifier 11 is connected parallel to rectifier 9 and successively with capacitance 12, but for occurrence reverse rectifier 9, for the purpose that, when suitably chosen values of capacitances and resistances can be measured in

CL JO will be higher than the potential of point 6. At the rest of the time, the current in the circuit: rectifier 7 / - capacitance 72 will not pass. Thus, capacitance 72 is ultimately charged to a voltage Vmax - nin, which can be measured directly by instrument 75.

If the voltage measured at the ends of the resistance 3 is measured with a DC voltmeter J4, a value will be found. There is no need to turn on the voltmeter J4 parallel to the resistance 3. This same voltmeter, adventure to points b and 7, itself can play the role of leakage 3, if its resistance is chosen appropriately (Fig. 2).

Thus, the modulation depth coefficient / C can be determined based on the readings of instruments 7J and 74.

Both measuring devices 13, located so, their arrows moved on the same scale, make it possible to carry out the device according to Ferrieux.

However, it is not particularly convenient to produce readings on the curved scales of such a device and it is more rational to carry out a device that directly gives K by combining the moving parts of both measuring devices 13 and 7 into one system, so that non-absolute values of stresses are noted. Y and V -

- Kmin attitude. A static voltmeter can be used for the measurement, however, the complexity of manufacturing them, as well as the fact that when using this kind of device, as well as any other device blocking the path to direct current (lamp voltmeter), it is necessary to provide a leak for 72-bit capacitor discharge in favor of the use of direct current devices.

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The use of a direct current device for the above purpose introduces a fundamental error in the measurements, but a simple calculation shows that it is technically quite simply possible to achieve an accuracy that fully satisfies all practical requirements. Indeed: the DVI device consumes about 60 microamperes; under stress

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on the order of 240 volts, leakage 15 can be taken equal to 4 megohms. If the capacitance of the capacitor 72 is 0.05 tsR, then in 1/100 sec, the capacitor 72 has time to be reduced by 5% and the reading of the voltmeter 13 deviates from the true value is about 2.5%. For all frequencies above 100, the accuracy is significantly increased and already at 300 periods per second the instrument error does not exceed 1%.

If desired, accurate measurements can also be made at low frequencies (for example, 50 lane). The readings of the instrument can be easily corrected by multiplying by constant coefficients corresponding to the frequencies at which the measurement is performed.

If used to determine

Claims (4)

1 / Wed and Vniax- min Permanent Instruments current, the independence of the readings of the modulation depth gauge from the absolute values of the voltages is achieved extremely simply by applying the constant current device described above to any device 16 showing the ratio of currents, for example, with two mutually perpendicular coils placed in a common magnetic constant field (like an ohmmeter) or a combination of two sub-systems located in two unequal magnetic fields, one of which, at least, varies in intensity depending on the angle "(Fig. 3). In devices of this type, all extraneous guiding forces must be minimized. In the absence of currents, the indicator is in indifferent equilibrium and its position is fixed only by the action of the forces caused by the currents passing through the mobile system. If it is impossible to directly use the currents, due to their smallness, it is possible to amplify one of them or both by any known method that guarantees the preservation of proportionality during amplification. The scheme described above also makes it possible to determine the magnitude of the modulation asymmetry, since the value required for this is obtained by measuring the voltage on the capacitor 8. capacitors 5, 8 and 12 are proportional to the average amplitude, maximum amplitude and difference, between the maximum and minimum voltage or current amplitudes. 2. The form of the device according to claim 1 for measuring the modulation coefficient, characterized in that the measuring instruments included: one J4-in circuit b, 7 and the other 75-to capacitor terminals / 2, are arranged so that their intersection point The indicators indicated on the scale the modulation coefficient regardless of the absolute values of the currents passing through the instruments / 5 and 74. 3. In the device according to claim 1, use a measuring device adapted to directly measure the relationship of electrical quantities and connected by one part of its system to circuit 6, 7, and the other to terminals of capacitance 72 and marking the ratio of the amplitude difference to their average value, calibrated in modulation coefficients. 4. Change the device according to p. 2 and 3, characterized by the use of a measuring device 75 or a device 76 that reacts to a current passing through a leakage resistance 75 connected in parallel with the capacitor 72 (Fig. 3). fip1 e "fig / fig2 4" iS fipz. flF lLVlLi b-. FIG. In r. 8 WwWMmMnV