SU834528A1 - Current value voltmeter - Google Patents

Description

The invention relates to a ritepical technique and is intended for use in realizing digital control of alternating voltage. A device is known that provides a measurement of the effective value of a strand and contains, in particular, consistently connected functional blocks of squaring, averaging, and extracting the square root l. The disadvantages of the known device are in significant inertia and large measurement errors while monitoring the effective voltage values in a wide dynamic range. The closest technical solution to this invention is an effective value voltmeter, the action pinch of which is based on the time and time comparison of the actual value of the measured voltage and the constant compensating voltage, at which the process of selecting the compensating voltage equal to the effective value of the measured voltage is carried out in the second cycle of the operation of the device by discrete balancing. The voltmeter contains a quadratic voltage-to-frequency converter, the output of which is connected to the counting inputs of two pulse counters through appropriate keys, a code comparison unit whose information inputs are connected to the outputs of pulse counters, a compensating voltage driver, a switch, a control block, one of the inputs of which is connected with the common input of the device and the first input of the switch, another input with the output of the code comparison unit, and the outputs with the control inputs of the keys, pulse counter, pho tors, compensates for the voltage in the switch 2. The drawbacks of the known device are also associated with significant inertia and tangible errors of the large duration of each cycle of the device function, and the error in the presence of the amplifier drift in the voltage-to-frequency converter and the asymmetry of the reference voltages.

The purpose of the invention is to increase i speed and accuracy.

The delivered circuit is achieved by the fact that in a voltmeter of the effective value, containing a quadratic voltage-to-frequency converter, the output of which is connected to the counting inputs of two pulse counters through the corresponding switches, the code comparison unit, the information inputs of which are connected to the outputs of the counters of pulses, the compensating voltage generator switch, a control unit, one of the inputs of which is connected to the common input of the device and the first input of the switch, the other input to the output of the comparison unit and outputs with control inputs of keys, pulse counters, compensating voltage driver and switch. A voltage pre-evaluation unit, a polarity reversing unit, an analog adder and a source of additional voltage are added, and the voltage pre-evaluation unit input is connected to the output of one of the pulse counters, and the output to the control input of the source of the additional voltage, the signal input of the block | polarity changes are connected to the corresponding output of the compensating voltage generator, the control input is connected to the corresponding output of the control unit, and the output is connected to the second input of the switch, the inputs of the analog adder are connected to the outputs. ... the switch and the source of the additional voltage, and the output to the input square of the chganic voltage-to-frequency converter.

The drawing shows a functional diagram of a voltmeter acting a a4 & Kvta.

The device includes a switch 1, an analog adder 2, a control block 3, a quadratic voltage-to-frequency converter 4, keys 5 and 6, counters 7 and 8 pulses, a code comparison block 9, a voltage pre-estimate block id, a source il additional voltage, unit 12 changes in polarity and the shaper 1 3 of the compensating voltage.

The operation algorithm of the proposed current-voltage voltmeter is based on a short-term comparison of the effective value of the measured voltage and the constant compensating voltage, with the measurement process being preceded by a preliminary clock, during which the preliminary voltage is estimated. If the effective value of the voltage belongs to the lower part of the instrument scale, then in the next cycle, the sum of the measured and some constant additional voltages is stored, and the discrete equilibration. In the subsequent cycles, the sum of the compensating and additional voltages with the change of the field compensating voltage in the middle of each measure. If . effective value of the measured napa; If the voltage belongs to the upper part of the instrument scales, the conversion process is performed in the same way, however, the additional voltage in all cycles is assumed to be zero.

The device operates in three cycles. In the first cycle, switch 1 is in the upper position, key 5 is open, and key 6 is closed. On the c. The turn of the voltage converter 4 to the frequency, the measured voltage Uy arrives. During the first cycle T in the pulse counter 7, the number of pulses NJ I is accumulated corresponding to

t

M; - fi (t) ,, y

where (Jy is the actual value of the measured voltage,

if (t is the reference voltage and the frequency of the Converter 4 voltage to frequency,

§ is the coefficient determined also by the parameters of the converter 4.

The task of preliminary estimation in block 10 of preliminary estimation of voltage consists in finding out whether a factor exceeds or not V) (half of the dynamic range of the instrument Vc.

Claims (2)

By the formula (1), it is possible to calculate in advance at the design stage the number I corresponding to the value Uyu. In this case, block 10 will determine the ratio of the numbers N and. If I means Vy Vj (and you need to add an extra voltage. Conveniently, if NJ, then UX VXH and enter Convenient. There is no need. In practical implementation of the device it is convenient to set such a number of pulses NUQIV in the counter of 7 pulses before starting the measurement where NO is the capacitance of the counter 7. Then, with the help of V), the unidag state of the high-order trigger of counter 7 will correspond, and the case. Thus, the unit 1O is the preseed voltage. It is a logical element that determines the state of the trigger of the higher bit of counter 7 and generates a corresponding signal. depending on the result of the preliminary injection, the unit U is outputted to the source of the additional voltage AND for connecting or not connecting the additional voltage. At the end of the first cycle, the pulse counter 7 is reset to nix. In the second pick, the duration of which is also equal, the position of the switch 1 and the state of the keys 5 and 6 do not change, but to the second input is analog. The adder is supplied by Convenient. (consider the case when the measured voltage belongs to the bottom of the scale). The input is Vx (t) Wx () + Xwjg. At the end of the second cycle, the number 7 in the counter 7 is equal to N.SVJ VSVJV & V ,, 5; T (In the third cycle, consisting of several cycles, the duration of each of which corresponds to T, switch 1 is reduced to the lower position, key 5 is closed, and the key 6 is cleared. The process of selecting the compensating voltage V, equal to the actual value of the voltage / x, is carried out. Selection of the required value for the voltage of the voltage V is performed in bits by means of the interactive connection of the values of X and J T to the input of the voltage converter 4 and h Evaluation of the ratio of Vy and V ,, is made on the basis of a comparison of their average squares, the values in the counter 7 and 8 pulses, which is carried out using block 9 of code comparison, Depending on the ratio of the discretely typed voltage V and voltage Vx, block 9 gives signal about the need to decrease or increase VK. At each equilibration cycle, the input signal K is applied to the input of converter 4. At the moment corresponding to the middle of the cycle, the sign of the compensating voltage Vy changes. At the end of each cycle, the number of sv, 4, is recorded in the counter of 8 pulses. (four). The measurement process ends when such a value V is selected, at which NN (2. Then, for {5) equal right parts of equalities (3) to (4), we obtain V, (5) The control code of the compensating voltage generator 13 s turns out to be proportional Acting to the value of the measured voltage. It can be shown that with the implementation of the change in polarity of the compensating voltage, carried out by block 12 in the middle of each cycle in the third cycle, the linearity of the voltmeter conversion function is ensured. The awnings of exactly Y | y, not Ldg, are due to the correction occurring in the problems caused by the influence of the additive zero bias of the amplifier and the asymmetry of the reference voltages in the voltage-to-frequency converter 4. The measurement process of the proposed device consists, as already mentioned, of three Shshlov, and the duration of the first and second cycles in the amount does not exceed 2T, and in the third cycle you need the same number of cycles as in the known device. Due to the fact that the duration of each cycle in the proposed voltmeter is sharply reduced, an increase in the speed of the instrument is achieved. In the proposed device, both the multiplicative and additive components of the error of the converter 4 are corrected, in connection with this, the accuracy of the measurement of the effective voltage value is improved. Increasing the speed and accuracy of the device expands the dynamic range of measured voltages. The invention The effective value voltmeter, containing a quadratic voltage-to-frequency converter, the output of which through the corresponding switches is connected to the counting inputs of two pulse counters, a code comparison unit, whose information is connected to the outputs of the pulse counters, a compensating voltage generator, a switch, a block control one of the inputs of which is connected to the common input of the device and the first input of the switch. The other input is with the output of the code comparison unit, and the outputs are with the control inputs of switches, pulse counters, a compensating voltage driver, and a switch, characterized in that. In order to increase speed and accuracy, a voltage pre-evaluation unit, a polarity reversing unit, an analog adder and an additional voltage source are introduced, the input of the voltage pre-evaluation unit connected to the output of one of the pulse counters, and the output to the control input of the source of the additional voltage, the signal input of the reversing unit is connected to the corresponding output of the compensating voltage driver, the control input is connected to the cooTW output of the control unit, and Exit - to the second input of the switch, the analog adder inputs are connected to outputs of switch and .k additional voltage source, and vyhodKD quadratic input transducer voltage to frequency. Sources of information taken into account in the examination 1. USSR author's certificate number 222735, cl. H 03 K 13/20, 1967. 2. USSR Authorship Certificate No. 367389, Class A 19/26, 1971.