SU414497A1 - METHOD OF PULSE PRESENTATION OF ELECTRIC HOMES OF INDUSTRIAL FREQUENCY AT PRECISE DISTANCE MEASUREMENTS OF LOW TEMPERATURES - Google Patents

Description

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The invention relates to methods for the pulse suppression of electrical noise at industrial frequency during precision remote measurements of low temperatures in cryogenic engineering.

The known methods for improving the noise immunity of the measuring system in the implementation of pulse methods are based on the sensor supplying current pulses. At the same time, the signal-to-interference ratio is improved by reducing the time of the supply pulse while maintaining its power, and the sensitivity of the system to voltage is increased without increasing the average power dissipation on the sensor. The interference is not completely destroyed.

Pulse filtering requires sophisticated devices that allow the phase adjustment of the pulse element to match the phase of the interference, for example, a noise amplifier that controls the pulse element from this interference.

The aim of the invention is to develop a method for more fully suppressing electrical noise of industrial frequency when measuring low temperatures in a cryogenic technique, in which it will be possible to use precision electronic measuring equipment.

This goal is achieved due to the fact that, according to the proposed method, the sensor is powered by constant-polarity pulses with a follow-up frequency of supply pulses equal to twice the frequency of the supply network, followed by multiplying this sequence by minus one unit through one pulse, pulse sequences at the time of each pulse amplitude value for the time between pulses and amplification of the received signal.

The present method makes it possible to completely eliminate the influence of network frequency interference on the measurement result and to ensure high accuracy of the sensor with precision remote measurements of low temperatures.

FIG. 1 shows a part of the flowchart of the measuring system that implements the proposed method; in fig. 2 - time waveforms showing the output waveform of the corresponding block circuit element.

Sensor 1 is connected to a source of direct current voltage 2 through a switch K, which is controlled by a generator of 3 pulses synchronized with the supply network 4 and ensures that the pulses follow a double frequency of the network. Pulses modulated by amplitude with temperature t acting on sensor 1 enter the sigpal transmission line 5, where they are superimposed on a signal of industrial frequency interference. At point a, the signal is summed with the negative feedback signal, and the received signal arrives at the key K.2, which multiplies by -1 the signal through a single pulse using the inverter 6. The key / Cs working in phase with the pulses of the useful signal arriving from the line, it transmits the instantaneous values of the signals that are stored on the memory element 7 until the arrival of a new pulse. Next, the resulting signal is supplied to the AC voltage amplifier 8 and the demodulator 9, from which the DC voltage is applied to the output meter, and if necessary to the negative feedback circuit.

Thus, in suppressing the interference of the network frequency in this way, the dependence of the power supply mode of the sensor on the amplitude of the interference is eliminated and the dependence of the degree of suppression of the interference on its phase is eliminated.

Subject invention

The method of pulsed suppression of electrical noise of industrial frequency with precision remote measurements of low temperatures using a resistance thermometer powered by current pulses, characterized in that, in order to more completely suppress the electrical noise of industrial frequency, the resistance thermometer is supplied with current pulses of constant polarity following supply pulses equal to twice the frequency of the mains supply, followed by multiplying this sequence by minus one through one pulse, Inan amplitude values of the resultant pulse sequence at the time of action of each pulse amplitude values for a time between pulses and the gain of the received signal.

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