RU1788475C - Measurement method for electric signal extreme values - Google Patents

Abstract

Usage: the invention relates to measuring and computer engineering and can be used in measuring and information systems. SUMMARY OF THE INVENTION: a method of measuring the extremes of an electrical signal, which, at the moment of equal current value with a threshold value, starts the first measurement cycle, simultaneously counting the number of pulses of the reference sequence and summing the sample of instantaneous values of the signal under study at equal time intervals determined by the pulse period reference sequence. At the moment of changing the sign of the difference between two adjacent samples, the first number m of counted pulses, the penultimate sample value -Yni, and the accumulated first sum Si are stored. Then the second measurement cycle is started, remembering the next sampling value of the studied signal Y21, at the same time counting the number of pulses of the reference sequence and summing the sampling of instantaneous values until the value of the second sum S2 becomes equal to the value of the first sum Si, at this moment the measurement is completed, memorizing $ 2 and P2. The coordinates of the extrema are determined by the formulas given in the description of the invention. 3 sf fields, 3 yl. THX

Description

The invention relates to measurement and computer technology and can be used in information-measuring systems for the analysis of random electrical signals against a background of interference.

A known method for measuring the extremes of electrical signals, based on the differentiation of the signal, is implemented in devices. A significant drawback of this analogue method is the low noise immunity due to the fact that due to the differentiation of the signal

the signal to noise ratio at the input of the meter decreases.

Closest to the invention in technical essence is a method for determining the extremes of an electrical signal, based on the indication of a change in the sign of the difference between the current and previous coded values of the signal under investigation, implemented in the device. This method is contemplated as a prototype.

The disadvantage of this method is the low accuracy of measuring the extremes of the signal, especially low for small

N

with

(L

|

signal-to-noise ratios at the input of the meter: 3/1 ... 5/1. Such conditions are characteristic for the operation of on-board equipment of aircraft and sea vessels, and other mobile objects.

The purpose of the invention is to increase the accuracy of measuring the extremes of an electric signal at low signal-to-noise ratios due to the fact that not differentiation, but signal integration is used.

The essence of the invention lies in the fact that in the method of measuring the extrema of the electric signal, which consists in sampling the instantaneous values of the signal under investigation at equal time intervals m, determined by the pulse period of the reference sequence, count the number of pulses n, the reference sequence over a time interval from the beginning of the measurement of ti to the time of the extremum, and the achievement of the extremum is judged by the change in the sign of the difference between the current and previous values of the samples values of the signal under investigation, for the above purpose, the first measurement cycle begins at the moment the signal Y (t) is equal to the threshold value U, simultaneously with the counting of pulses of the reference sequence, samples of the instantaneous values of the signal under investigation are summed, calculating the value of the first sum Si 2 YH. at the moment r0, the sign of the difference between the current and previous values of the samples of the instantaneous values of the signal under study is memorized, the number of pulses m and the first sum Sr are memorized, as well as the penultimate value of the sample of the studied signal Yni Y (T0 - т), after which the second measurement cycle begins, for which remember the next sample value of the studied signal Y21 Y (r0 + r) Y (m + 1) r, count the number of pulses P2 of the reference sequence and summarize the samples of the studied signal, at the same time calculating the value of the second sum $ 2 2 Y2i, d points in time t2 when the second sum value a ref with the first sum, wherein the equation of Si and 52 is judged by the execution condition

Si - AS $ 2 Si + AS, where AS is the specified absolute error of comparison, the values P2, S2 are stored. and the sought coordinates of the extremum are determined by indirect measurement formulas

52 / P2

tm

Si / m + 52 / P2

(P1 + P2) G, (1)

0

5

Ym $ 1 / Щ2 + 52 / п2 Yn1 +

Si / m

 Y21 +

Si / m + 52 / P2 - 52 / P2

Y21

(Ynl-Y2i), (2)

Sl / fll + 52 / P2

why, in direct measurements, the threshold value U is set corresponding to the condition:

0 U / a to {h / 2,

(3)

where (C is the standard error of the means of direct measurements, h is the signal-to-noise ratio in direct measurements.

The period of pulses of the reference sequence is selected from the condition

1 v g / Dt | Ti / Dt. , (4) where t and 12 - ti are the duration of measurements

 interference correlation interval.

The absolute error A S comparing the values of the sums of Si, S2 is chosen from the condition:

ASЈ

1 U

.(5)

In FIG. 1 illustrates the main process parameters used in formulas (1), (2) for indirect measurement of maximum coordinates (minimum is determined similarly), FIG. 2 is an illustration of the balance of moments used for noise-tolerant estimation of the moment b, extremum Y m of the signal Y (t) (asterisks indicate estimates of the coordinates of the extremum), FIG. 3 is a structural diagram of a device that implements the method.

The fundamental ratio for obtaining the indirect measurement formulas (1). (2) found by the moment balance method -U

J.Y (t) dt Sl / ni (tm-tl) 52 / P2 (t2-tm)

tl

45-Jv (t) dt,

(6)

where the average value of the signal yi ° Si / ni in the interval ti, tm and the average value of the signal y2 ° 52 / P2 in the interval tm, TV play

0 the role of forces, and the lengths of time intervals b, - ti and 12 - tm - the role of the lengths of levers (see Fig. 2). The moment ti 0, the moment t2 are determined from the condition that the sums Si are equal, $ 2, and the extremum moment mt from equation (6). Moment 0

5, the end of the first summation and the value of Yni are determined, as in the prototype, by changing the sign of the difference Yni - Y2i.

The number of pulses m and P2 is determined by the length of the intervals tm - ti, ts - tm and the duration U of the generator period of the calibrated pulse sequence. An estimate Y m of the extremum value Ym is defined as the weighted average of the samples Yni and Y2i:

Y tm / t2 Yn1 + Y21 Y21 + + tm / t2 (Yn1 - Y21). (7)

From (7) after the simplest transformations follows (2).

The mean and variance of the estimate (7) are determined by the relations

  a + (1 -a),

    +. (1 -a), (8) where the parameter is a ni / (m + n2).

If the measuring signal

Y (t) X (t) + | (t), (9) where X (t) is the useful signal (see the dotted line in Fig. 1).

Ј (t.) - stationary Gaussian noise with zero mathematical expectation and dispersion D Ј (t) o | then

  - a + (1 - «), (10)

Dry 1- M2r | 1n2 L, 2

 m J - L1 -----) (% (m + P2)

 The invention is carried out using the apparatus of FIG. 3.

A device that implements the method includes a measurement signal source 1. A sampling and storage unit 2, a signal threshold value source 3, a time stamping unit 4, a counter unit 5, an adder unit 6, microprocessor controllers (MPCs) 7, 8 that together control operation of all functional blocks, and they process the results of indirect measurements according to formulas (1), (2).

The device operates as follows. The IPC 7 gives the command to start the measurement on the IS 1 and on the IP 3. By this command, the measurement signal Y (t) and the signal U are received on the BFM 4. At the first output of the BFM 4, at the moment ti of the first match of the current value Y (ti) with the threshold U when Y (n) U, the start pulse of the GCBI BX2 start is generated and starts taking samples Yj of the signal Y (t) at times ti, ti + t, ti + 2 t, ..., ti + i g. The count pulses from BVX 2 are sent to the BSC 5, in the first counter of which the number ni is generated, in parallel, the samples YJ of the signal are sent to the BSM 6, where they are accumulated in the first adder as the sum Si S YI. At the same time, the samples Yi arrive at the BFM 4, where the difference D YJ YI + i - YI is formed from them. The sign of this difference sig AYj is determined. When changing the sign of the difference at the moment Ј0, the BFM 4 identifier gives the command to the first counter

5 to stop the count and write the number m in the first register of the IPC memory 7. At the same time, the same command ends the summation of the samples in the first adder BS b, the sum Si and the last sample in it Yni are recorded in the second and third registers of the IPC memory 7. At the next clock when m r + r0, the second counter of the SSN 5 is turned on, where

the number n2 begins to form, and in BS b, from the count of Y21. which is initially recorded in the fourth memory register of the IPC 7, the second summation begins on the second adder BS 6. The current value of the sum S2

enters the RAM IPC 7 and is compared with the value of the sum Si. When at a certain P2 step S2 Si ± & S, the IPC 7 identifier instructs the BFM 4 to generate a mark t2 of the end of the count and the end of the cycle, all the initial data of indirect measurements are formed, i.e., the results of direct measurements: Yni. Y2i. m. n2, Si, S2. IPC 7 and IPC 8 go into the mode of coordinated processing of measurement results according to formulas (1) and (2). The encoded values of Tm and Yt are taken from the IPC 7 and IPC 8 data bus.

To assess the positive effect of the application of the proposed method in comparison with the prototype, the following index indicator is used to increase the measurement accuracy (in times)

W 1

P1 + P2

,

C - P | -1U | / V1MrVo.lAl7

1 2 m

(eleven)

(P1 + P2) 2

0 Tests have shown that even at high levels of noisy harmonic | -1. (7X

signal - | g 1.73 - is provided

the relative stability of the measured 5 values and the reduction of the measurement error in comparison with the prototype in 1.21 - 1.8 times. The test results under various conditions show that the proposed method is useful both because of an increase in the accuracy of measurements under interference conditions, and because of the elimination of the systematic error that is typical for the prototype. A positive effect is achieved essentially by filtering the readings of the measuring signal at the intervals ti, tm, tm. 12. For random useful signals, the beneficial effect increases as the bandwidth of the interference spectrum grows relative to the spectrum band of the signal, and also as the number of the measurement period increases. So, for example, the relative error

measuring the zeros and extremes of harmonic oscillations against the background of a Gaussian noise at h 3 in the first measurement period is (-8.49 ... 10.8)%, and in the sixth (-0.983 ... 1.06)%.

Claims (4)

SUMMARY OF THE INVENTION 1. A method for measuring the extremes of an electrical signal, which consists in sampling the instantaneous values of the signal under investigation at equal time intervals m, determined by the pulse period of the reference sequence, counting the number of pulses n of the reference sequence over the time interval from the start of measurement T1 to the moment extremum, and the achievement of the extremum is judged by measuring the sign of the difference between the current and previous values of the samples of instantaneous values signal, characterized in that, in order to increase the accuracy of measurements of the coordinates of the extremum of the signal under study at small signal-to-noise ratios, the first measurement cycle begins at the moment the signal Y (t) is equal to the threshold value U, at the same time as the pulses ni of the reference sequence are calculated sampling the instantaneous values of the investigated signal, calculating the value of the first sum Si YH, at the moment t0 of the sign change the difference between the current and previous values of the samples of instantaneous values of the signal under study remembers the number of pulses u and the first sum Si, as well as the penultimate value of the sample of the signal under investigation Yni Y (T0 - m), after which the second measurement cycle begins, for which the next sample value of the studied Signal: Y21 Y (G0 + g) Y (n + 1) t, count the number of pulses of the reference sequence pa and sum the samples of the signal under study, simultaneously calculating the value of the second sum Sa Y2, until time ta. when the value of the second sum is compared with the value of the first sum, moreover, the equality of Si and S2 is judged by the fulfillment of the condition Si-AS 82- $ 81+ DZ, 0 where AS is the given absolute error of comparison, the values of P2, 82 are stored, and the sought coordinates of the extremum of the signal are determined by the formulas tm about. y-.2, about. Y- (P1 + P2) G 5 Yn Sl / ni + 52 / P2 32 / P2v Si / m + S2 / n2 Yn1 Sl / ni -Y21 Sl / ni + 32 / P2 0s / n  Y21 + fr7ni + S2 / n2 (Yn1-Y2l) 2. A method according to claim 1, characterized in that the threshold value U is set corresponding to the condition 50 h / 2. where is the standard error of the measuring instruments; h - signal to noise ratio, d 3. The method according to PP. 1 and 2, with the exception that the period of 2 pulses of the reference sequence is selected from the condition 1 t / DgЈ tn / Arj. ; 5 where chi is the duration of measurements (t2 - ti);  interference correlation interval. 4. The method according to PP. 1-3, characterized in that the absolute error of comparing the values of the first Si and second S2 sums is selected from the condition 1 U D5 AT Ok-sh