SU1762271A1 - Aperiodic process time constant meter - Google Patents

Abstract

The invention can be used as part of information-measuring systems and automated process control systems. The meter contains: 4 analog storage units (2), (3), (4), (5), 3 units of calculation (6), (9) (7), dividing unit (8), display unit (10) control unit (1). 6 - 7 - 8 - 10, 11 - 3-6 - 8, 11 - 4 - 9 - 7, 11 - 10. 2 type.

Description

The invention relates to measurement technology and automation and is intended to be used as part of information, but measure; Nyh systems and automated process control systems.

The aim of the invention is to extend the functionality of the constant-time meter of the aperiodic process to measure the constant time of both decreasing and increasing exponential signals with arbitrary initial and previously unknown set values of these signals.

Fig. 1 shows a diagram of a constant time meter for an aperiodic process (hereinafter, a meter); FIG. 2 shows diagrams explaining the operation principle of the meter.

Input terminal 1 is connected to the information inputs of analog storage units 2,3,4,5. The outputs of analog storage units 2 and 3 are connected respectively to the direct and subtractive inputs of subtraction unit 6. The output of subtraction unit 6 is associated with the inverse input of subtracting unit 7 and the first input of unit 8.

dividing and the output of subtraction unit 9 - with the direct input of subtracting unit 7, the output of which is connected to the information input of indicator 10. Five control outputs of control unit 11 are connected respectively to the control inputs of analog storage units 2, 3, 4, 5 and the indicator, and the input of the control unit 11 is connected to the trigger terminal.

The basis of the meter is based on the following considerations.

Aperiodic process can be described by one of two equations:

t U (t) A- (1-e) n C (1)

(for exponentially increasing signals) or

(L

 about go

hO

1) (t) A- e

}

„“

(for exponentially decreasing signals)

where A is the value of the maximum differential signal, characterizing the aperiodic process, between the time of the beginning of the process (t 0) and its completion (t °°); t - time

D is the initial value of the aperiodic process for a process of the form (1) iv-and a steady-state (asymptotic) value for a process of the form (2); r - time constant.

From (1) for arbitrary times tint can be written

U (ti) -Ra

1 - & U (t2) - p Ae g

then, taking into account (1) and (3), we get: u (ti) A-rU (ti) + C

ll {t2) -A-rir (t2) + С From (4) the required quantity follows:

t yj ± i) tJ 11

U (t2) -U (ti)

The value of m. Derived from (5) will also be valid for aperiodic processes of the form (2), as is easily seen, substituting (2) into (5).

To determine derivatives, we use the discrete differentiation method:

U (ti)

U (ti) U (ti + At)

At

U

(ta) -UlJLLrU (tt + At)

After substitution of (6) in (5), we obtain the expression

g y (alone

 Al U (H) -U (12)

"T-IGTT7) -1 and (h -FAI) -and (h + AI

T)

which is the basis of the meter.

The meter works as follows.

The signal characterizing the aperiodic process, U (t), (see figure 2) through the input terminal 1 is fed to the inputs of analog storage devices 2,3,4,5.

At consecutive times ti b + At. t2, t2 + A t, the control unit generates short control pulses (Ui, L) 2, U3, U / in Fig. 2). which are fed to the control inputs of analog storage units 2.3,4,5 and the latter fix the voltage values at these time points on the CROHX outputs

U (ti), U (ti + A t), U (t2), U (t2 + A. The duration of the short control pulses are selected from the condition:

- for the duration of the control pulse, the 5-pulse should almost

not changed;

- for the duration of the control pulse, the analog storage device must record the signal U (t) with

Yu error determined by the error meter.

The interval At is selected from the condition for determining the derivative by the method of discrete differentiation with the required

15 error. The interval ta - ti 0 is theoretically not limited, but it is also determined based on the required accuracy of the meter and its speed. To increase the speed of the meter

20 it is desirable to go to moment 0 near t 0.

The output signals of the analog storage units 2-5 are fed to the inputs of the exchangers 6 and 9 in accordance with FIG. 2 and

25, the output of subtraction unit 6 forms the difference U (ti) - U (t2), and at the output of subtraction unit 9 - the difference U (ti + At) - U (t2 + At). These differences go further to subtraction unit 7 and at its output a value is generated,

30 is equal to the denominator of expression (6), which enters the input of the Denominator of the dividing unit 8, at the input of which the signal comes from the output of the analog storage unit 6.

35 As a result, at the output of block 8 division

after the time t2 + At (plus the amount of delays in the channels of the meter blocks), the value of the desired value of the constant time t is formed.

40 Since the interval At is fixed, then in expression (6) it plays the role of a constant coefficient and can be taken into account in the transmission coefficient of subtraction unit 7 or division unit 8.

45 at time ts t2 + At + 13ad. where tsad is the signal setup time with the required accuracy in the meter units, the control unit 11 generates a control pulse 1/5. which arrives at the input of the right side of the indicator 10. Indicator 10 fixes the value of a constant time r and displays it on its scoreboard.

The control unit is a set of series-connected pulse formers and stand-by multivibrators.

Claims (1)

Claims of the Invention A constant-time meter for an aperiodic process containing an input terminal, two analog storage units, a subtraction unit, a dividing unit, and an indicator differing in that. that, in order to expand its functionality, two analog storage units, two subtractors, a control unit and a start terminal connected to the input of the control unit, the first, second, third and fourth outputs of which are respectively connected to the first inputs of the first, second , the third and fourth analog storage units, the second inputs of which are connected to the input terminal, and the outputs of the first and second analog storage units are connected to Here, respectively, the direct and inverse inputs of the first subtraction unit, the output of which is connected to the inverse input of the second subtraction unit and the first input of the dividing unit, when the output of the third and fourth analog storage units are associated with the third and fourth subtraction, respectively which is connected to the direct input of the second subtraction unit, the output of which is connected to the second input of the division unit, the output of which is connected to the first input of the indicator, the second input of which is connected to the fifth output b control lock . one FIG. 2