RU2019834C1 - Method of measuring voltage of single pulses - Google Patents

Abstract

FIELD: measurement technology. SUBSTANCE: method is based upon sequent charging of capacitors of peak detectors. Capacitor of peak detector is discharged through capacitors of the next peak detectors after voltage achieves maximal value through winding of the transformer. Time constant of the transformer excesses over duration of leading edge of the pulse of charge of discharged capacitor. EFFECT: improved precision of measurement; improved reliability. 1 dwg

Description

 The invention relates to measuring technique and can be used to measure peak voltage values of single pulses with a duration of 10 ... 100 ns.

To measure the voltage of single short pulses, peak detectors based on the charge of capacitors through low resistance and their discharge through high resistance are used [1]. Using one cascade of peak detector, the pulse duration can be increased by 10 ³ times. But as often happens, such an increase in pulse duration is not enough. Therefore, to memorize and store information about the voltage of a single pulse, methods of digitally converting the voltage into a code and a method for cascading the value of the amplitude of the pulse by peak detectors are used. Digital conversion of a single pulse voltage into a code allows you to store information until a "Reset" command is issued.

 But along with this advantage, this method has disadvantages, which include ensuring the linearity of the discharge of the peak detector capacitor; cyclicity of voltage to code conversion.

 Therefore, devices with digital conversion of the pulse amplitude are difficult to implement and are characterized by the fact that for some time the conversion input is closed, since the process of converting the pulse amplitude to the code occurs.

 The method of cascade charging of capacitors of peak detectors is free from these drawbacks [2]. With their help, it is possible to continuously control the amplitude of single pulses, the appearance time of which is random. Along with this, devices that implement this method of measuring the amplitude of single pulses have a simple circuit solution. However, they have a large dynamic error in the change in the amplitude of the pulse, caused by the dependence of the amplitude of the output voltage of the peak detector on the duration of the measured pulse. In [2], to eliminate this error and increase the information storage time, a method of cascading increase in the discharge time constant of the storage capacitor is used.

 An increase in the nominal value of the peak detector capacitance also leads to an increase in the dynamic error, since the voltage value at the output of the peak detector depends on the front of the measured pulse.

 For most of the coinciding operations, a method based on converting the pulse voltage to quasi-constant by sequential charging of the capacitors of the peak detectors is selected as a prototype. This method of measuring the amplitude of a single pulse allows you to measure the amplitude using simple DC devices. But when changing single pulses of duration 10.. . 100 ns they have a large dynamic error. This is because the voltage across the capacitor of the peak detector depends on the duration of the front of the measured pulse [3].

 The purpose of the invention is to improve the accuracy of measuring short pulses.

 This goal is achieved by the fact that in the method based on the sequential charge of the capacitors of the peak detectors, the capacitors of the peak detectors are discharged to the capacitors of the following peak detectors after the voltage across them reaches a maximum value through the transformer windings. In this case, the transformer time constant is longer than the duration of the front of the charge pulse of the discharged capacitor.

 A comparative analysis of the proposed method with the prototype shows that the claimed method differs from the known one in that the capacitors of the following peak detectors are charged by discharging the capacitors of the previous peak detectors through the transformer winding, the capacitors of the previous peak detectors are discharged after the voltage across them reaches a maximum value, constant time of the transformer should exceed the duration of the front of the charge pulse of the discharge capacitor.

 The drawing shows a device that implements the proposed method.

The device contains 1i-n - pulse front extenders, 2 - peak detector, 3 - n - maximum detection unit; 4 - key, 5i - transformer, 6 - recorder. The blocks are interconnected as follows. The input 1 _{1 of the} first extension of the front of the pulse receives the measured pulse U _x . The input of the pulse front extension 1 _i is connected to the inputs of the peak detector 2 and the maximum detection unit 3. The output of the peak detector 2 is connected via a key 4 to the output of the pulse front extension 1 _i to which the primary winding of the transformer 5i is connected. The key 4 is controlled using block 3. The secondary winding of the transformer 5i is connected to the input of the next extension 1 1 _{+ 1 of the} pulse front.

The secondary winding of the last transformer 5n is connected to the input of the peak detector 2 _n . The output of this peak detector 2 _{n is} connected to the input of the recorder 6.

 The device operates as follows.

When a pulse U _{x arrives} at the input of the first extender 1 _{1 of the} pulse front, the capacitor of peak detector 2 is charged to a value proportional to the amplitude U _x . After U _x passes its maximum value, the maximum determination unit 3 is activated and discharges the peak detector capacitor 2 through the key 4 to the primary winding of the transformer 5 ₁ . The time constant of the transformer 5 ₁ exceeds the duration of the front of the measured pulse U _x . Therefore, the front of the pulse at the input of the second extension 1 _{2 of the} front of the pulse also exceeds the front of the measured pulse. In this regard, the capacitor of the peak detector 2 of the second pulse front extender 1 ₂ is selected more than the capacitor of the peak detector 2 in the first pulse front extender 1 ₁ as many times as the pulse front length of the extension 1 ₁ exceeds the measured pulse front U _x .

So there is an extension of the pulse front in each extender 1 _i . The number of cascades of extension of the pulse front depends on the time constant of the recorder 6 and on the necessary accuracy of measuring the amplitude of the measured pulse U _x . That is, how much can the discharge of the capacitor of the last peak detector 2 _n be allowed to register its output signal with a given accuracy. Using the proposed method and the proposed device, the amplitude of the pulses was measured, the duration of which was 10 ˙ 10 ^-9 s.

The duration of the measured pulse in the present method is limited by the speed of the elements used in the peak detector 2 of the first extension 1 _{1 of the} pulse front. The error caused by the discharge of the capacitor of the first peak detector 2 due to the delay in the operation of the key 4 can be compensated by the transformation coefficient of the transformer 5 ₁ . Therefore, theoretically, using the proposed method, it is possible to measure the duration of an arbitrarily short duration, since it is based on increasing the front of the pulse supplied to the next peak detector.

 In the following peak detectors, capacitors can be used whose capacitance is many times greater than the previous ones, how many times the pulse front at the transformer output increases.

Claims (1)

 METHOD FOR SINGLE VOLTAGE VOLTAGE MEASUREMENT, which consists in charging the capacitors of the peak detectors with the signal under investigation, characterized in that, in order to improve the accuracy of measuring short pulses, the capacitors of the peak detectors are discharged to the capacitors of the following peak detectors through the transformers after the accumulated signal reaches a maximum, while the time constant of each of the transformers exceeds the duration of the front of the input pulse of the corresponding peaks oh detector.

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