RU1178224C - Method of monitoring insulation of pickup circuits - Google Patents

Abstract

METHOD FOR CONTROL INSULATION OF SENSOR LINES, which consists in alternately measuring the electrical characteristics of the lines of each sensor and comparing them with the reference ones, characterized in that, in order to expand the functional capabilities, the beginning of the measurement is synchronized with the zero phase of the mains voltage, the magnitude of the amplitude induced on the line is measured each interference sensor, compare this value with the maximum value acceptable for the given conditions and, if this value is exceeded, an error signal is generated.

Description

The invention relates to automation and information technology, and can be used in multichannel devices for measuring process parameters using sensors of electrical signals when operating under network interference conditions.

The purpose of the invention is to expand the functionality by providing control of the isolation state of sensor lines without interrupting the measurement of process parameters. .

In FIG. 1 is a functional diagram of a device that implements the proposed method. In FIG. 2 is a timing diagram of connecting sensors and measuring interference amplitude.

The device contains sensors 1 of electrical signals, the outputs of which are connected using the connecting lines to the corresponding information circuit

switch 2 inputs, output

from which it is connected to the information INPUT of an analog-to-digital converter (ADC) 3 and to the first input of the sensor parameter measurement unit k, the output of which is the information coming from the sensors 1, the network phase isolation unit 5, which is connected to the mains voltage by an input XI , and 00, the first output r to the second (control) input of the parameter measuring unit k and to the input of the address counter 6,

| 5. the output of which is connected to the control input of switch 2, the second output of the network phase extraction unit 5 is connected to the first input of register 7 and the first input. OR circuit 8, the output of which is connected to the triggering input of ADC 3, the first output of which is connected to the second input of the register 7, and the second output is connected to the third input of the register 7 and with the first input of the subtraction circuit 9, the second input of which is connected to the output of the register 7, and the output is connected to the first input of the comparison unit 10, to the second input of which the maximum permissible value code is supplied and you ode formed yn ravl fault signal is iso l tion, the third output of the block 5; phase separation of the network is connected to the second input of the circuit OR 8, The device operates as follows. The mains voltage is supplied to the input of unit 5. At the three outputs of the phase separation unit 5, pulses are generated at the moments of the phases of the mains voltage 7 .. About 2 s 2 rad, respectively. According to the pulse from the first output of the phase separation unit 5, the address counter 6 sets at its output a new address of the switch2, through which the next sensor 1 is connected to the measurement inputs of the unit. Measure the parameters of the sensors and ADC 3. The same pulse is applied to the trigger input of the measurement unit k parameters of the sensors, the process of measuring the parameter of the connected sensor 1 begins. At the same time at the time of the phase; the network is glad the pulse from the output of the phase separation unit is fed through the OR 8 circuit to the triggering input of the ADC 3, and also register 7 for recording information .. The time .preobrazovani ADC 3 should be a considerably smaller than the period mains voltage. The ADC 3 performs analog-digital conversion of the voltage on the sensor line. Thus, at the output of the ADC 3, a digital voltage KOfi is generated, which is the sum of the sensor voltage and the voltage of the induced network noise (see Fig. 2. Based on the ready signal generated at one of the outputs of the ADC 3s, the received code is written into register 7 and set At the moment of 3 phase of the network With g-1G I am glad the pulse from the corresponding output of block 5 of the isolation of the phase through the circuit OR 8 is fed to the triggering input of the ADC 3. In this case, the ADC 3 performs another analog-to-digital conversion of the signal on the sensor line (see Fig. 2), the result of which is fed to one of the inputs of the subtraction circuit 9. At the other input of the subtraction circuit 9, the voltage code obtained during the first conversion is set in this way. Thus, the voltage difference code on the line and the sensor measured in antiphase is generated on the output of the subtraction circuit 9. moments of time This difference is equal to twice the amplitude of the voltage of the network noise induced on the sensor line 1. From the output of the subtraction circuit 9, the difference code is sent to the comparison unit 10, where the code is also supplied. maximum permissible interference voltage. In comparison block 10, the obtained value of the interference amplitude is compared with the maximum allowable and the signal | - insulation fault signal is generated if the obtained value exceeds the maximum allowable, taking into account the error in determining the medium | its for given conditions of the level of interference and the error of analog-to-digital conversion. In the presented device, the control sequence is carried out. using a switch 2, which sequentially connects the sensor lines 1 to the measuring inputs of the sensor-4 and ADC 3 parameters. The switch 2 is controlled from the outputs of address counter 6 .. The phase-network isolation unit 5 synchronizes the entire operation of the device with the mains voltage , I form pulses at the corresponding outputs at the moments of the phases of the mains voltage CP., / at O, rad., - “- rad. At time q 0, the next state of the address counter 6 is changed (i.e., the next sensor is connected) and the measurement of its parameter is started by the sensor parameter measurement unit k. Darad and later, at moments of pleasure, two measurements of the amplitude are made on the connected line using ADC 3. The result of the first measurement is stored in register 7 and set from its outputs to one of the inputs of the subtraction circuit 9. The result of the second measurement is fed to the second input of the subtraction circuit 9, at the same time, at its output a magnitude of the frequency of two measurements is formed, which is equal to the amplitude of the network noise induced on the line of the network sensor (see Fig. 2). The obtained value of the amplitude of the network noise is compared in the comparison unit 10 with the maximum allowable value MjJiU, which can be determined once for this device and in the comparison unit 10, or

117822 4

it is also measured regularly by some device on the reference line. If the value of the interference amplitude exceeds the maximum allowable value, in the block of comparison 10 an insulation violation signal is generated.

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Figure 1