SU1797079A1 - Method of measurement of electric values of active resistance, induction and capacitance - Google Patents

Description

UNION OF SOVIET

SOCIALIST

REPUBLIC

„.SU ,,,, 1797079 A1 <505 G 0.1 R 27/26 __

STATE PATENT

DEPARTMENT OF THE USSR (GOSPATENT USSR)

DESCRIPTION OF THE INVENTION

TO AUTHOR'S CERTIFICATE (21) 4883340/21 (22) 11.19.90 (46) 02.23.93. Bull. No. 7 (71) Samara Polytechnic Institute. V.V. Kuybysheva (72) V.S. Melentyev, V.S. Baskakov, V.S. Shutov, A.A. Sokolov and A.A.Safonov (56) Copyright certificate of the USSR No. 1075192, cl. G 01 R 27/26, 1984.

Shlandin V.M. Digital measuring devices. M., Higher School, 1981, p. 179, fig. 3.36.

(54) METHOD FOR MEASURING ELECTRIC VALUES OF ACTIVE RESISTANCE, INDUCTIVITY AND CAPACITY (57) Use: in measuring technique. The proposed method serves to measure the resistance, inductance and capacitance. The inventive direct-capacitive or inductively-active measuring circuit, one of the elements of which is known, direct current voltage is applied, after a typical time interval from the moment of voltage supply, the first instantaneous voltage value is measured at the midpoint of the measuring circuit, after the same time interval from the moment The first measurement measures the second instantaneous value of the voltage at the midpoint of the measuring circuit and determines the unknown element of the circuit according to the formulas given in II inventions. 2 ill. 5 (/> s

The invention relates to measuring equipment and can be used in measuring instruments for active resistance, inductance and capacitance.

There is a method of measuring electrical quantities of active resistance, inductance and capacitance, which consists in converting the measurable value of the first element of a sequential active-inductive or active-capacitive measuring circuit, the value of the second element of which is known, into the time interval associated with the beginning of the aperiodic voltage setting process direct current on the circuit elements, the time interval is limited by the moment .. the equality of the absolute values of the voltage on the measuring elements circuit, and moreover, the moment of equality of these stresses is judged by the moment of equality to zero of the sum of the stresses on the circuit elements relative to their overall output.

The disadvantage of this method is the low speed, due to the fact that the measurement time of an unknown element of the electric circuit in proportion to its time constant cannot be less than 0.69 g

Closest to the technical nature of the proposed is a method of measuring electrical quantities of active resistance, inductance and capacitance, which consists in the fact that a sequential active-capacitive or inductively-active measuring circuit, one of the elements of which is known, is supplied with a direct current voltage of 1797079 A1 and measured the time interval from the moment the voltage is applied to the moment of equal voltage at the midpoint of the measuring circuit to the reference voltage, proportional to the unknown element of the meter chain oh.

The disadvantage of this method is the low speed due to the fact that the measurement time of an unknown element of the measuring circuit in proportion to its time constant t cannot be less than t. This limits the scope of this method in circuits with a large time constant.

The purpose of the invention is to increase the speed of measuring electrical quantities of active resistance, inductance and capacitance.

Ui, U2 - the first and second instantaneous voltage values at the midpoint of the measuring circuit.

In FIG. 1 is a temporary diagram 5 illustrating the proposed method; in Fig: 2 is a block diagram of a device that implements this method.

The essence of the method is as follows.

For an active-capacitive series circuit, when a DC voltage source is connected to it, the voltage at the midpoint increases in dependence. _ tu (t) = Uo (1-e ' ^f ). (1) where Uo ~ voltage of a constant source

This goal is achieved by the fact that 20 according to the method, which consists in supplying a series of active-capacitive or inductively-active measuring circuit, one of the elements of which is known, DC 25 current, after a typical time interval from the moment of voltage supply, the first instantaneous voltage value is measured at the middle point of the measuring circuit, after the same time interval from the moment of the first 30 measurements, measure the second instantaneous voltage value at the middle point of the measuring circuit and determine is Unknown circuit element by the formulas;

- for active-capacitive circuit 35

Cx =

current;

t is the current time from the moment the voltage source Uo is connected;

t = RC is the time constant of the circuit;

/ R, C - respectively, the resistance and capacitance of the circuit.

Through the time interval Δΐ from the moment the voltage source Uo is connected at the time ti (Fig. 1), the instantaneous value of the voltage across the capacitor • _Δι Ui = U _o (1-e. ^G ).

Through the time interval Δΐ from the moment of the first measurement at time t2 (Fig. 1), the instantaneous value of the voltage across the capacitor

2at

U ₂ = Uo (1 - e ^τ ).

P - ^{Δΐ x} G _1η ϋ2- ϋϊ ^{Co | p} ..... OF

Then,

- for inductively active circuit

Lx

Ro Δ t _ln U2-U1

At:

U2-Ui_Uo (l ~ e ^Г ) -U ₀ (le ui ~~~ ^: At ^τ )

Δ_τ

At -e ^τ , U ₂ - Ui ^{Rx _} —g

Uo (1, - e

At + e ^τ τ

Given that e '

we get

At τ · ₌

Δι _Δι e ^τ · e ” ^τ

At

U2 - Ui _ e ^τ Ui

At

- .. LJ

-e ' ^τ where Cx, R _x and Lx is the value of the unknown element of the measuring circuit;

Ro, Co and L _o - the value of the known element of the measuring circuit;

Δΐ - reference time interval;

Having prologged both sides of this expression, we obtain

At_ _lr , Uz-Ui t Ui from

At

Ua - Ui * Ur (2)

If the capacitance Cx is unknown, and the active resistance Ro of the measuring circuit is known, then m = RoCx and

C _x =

At (3)

Ro in

U2-U1

Ui

If the active resistance Rx is unknown, and the capacitance Co of the measuring circuit is known, then m = R _x Co and

Rx =

At (4)

With In

U2-U1 ϋϊ

For an inductively active series circuit, r = L / R and expression (2) is also valid.

If the inductance L _{x is} unknown, and the active resistance Ro of the measuring circuit is known, then tg Lx / Ro u. _ Ro At '- if the active resistance Rx is unknown, and the inductance of the measuring circuit Lo is known, then Lo / Rx and

Rx

(6)

The increase in measurement speed of an unknown element of the measuring circuit in the proposed method is achieved due to the fact that the measurement time does not depend on the value of the time constant of the circuit, but is determined only by the value of the model time interval At, which can be chosen arbitrarily small (At # 0).

A device that implements a method of measuring electrical values of active resistance, inductance and capacitance (Fig. 2), contains a DC voltage source 1, a key 2, a measuring circuit 3, made in the form of active co, resistance (or inductance) 4 and capacitance (or active resistance) 5, 5 analog-to-digital converter 6, computing unit 7, control unit .8, and the output of voltage source 1 is connected to the input of switch 2, the output of which is connected to the input of measuring circuit 3, 10 made in the form of a series connection active resistance (or inductance) 4 and capacitance (or active resistance) 5, one contact of which is connected to the device common bus, the middle 15 point of the measuring circuit 3 is connected to the input of the analog-to-digital converter 6, the discharge outputs of which are connected to the information inputs of the computing unit 7, and the control input - with the first 20 output of the control unit 8, the second output of which is connected to the control input of the key 2, and the third output - with the control input of the computing unit 7, the initial installation input of which 25 connected to the input of the control unit 8 and the Start ”bus of the device.

The device operates as follows.

After applying a pulse to the bus Start 30 'of the device, the computing unit 7 proceeds to the start of program execution. On command from the control unit 8, the key 2 is closed and the voltage Uo from the DC voltage source 1 is supplied to the input 35 of the measuring circuit 3. The voltage at the midpoint of the measuring circuit 3 changes according to expression (1).

Through the time interval At specified by the control unit 8 at the time 40 t ^, the ADC 6 is started, at the input of which the instantaneous voltage value is equal to u. This voltage is converted into a code, which is recorded in block 7 by the input request signal from the control unit 8 to the control 45 of the input of the computing unit 7.

Through the time interval At specified by the control unit 8, at time t2, the ADC 6 starts again, at the input 50 of which the instantaneous voltage value is U ₂ . This voltage is converted into a code, which is recorded on the input request signal in the computing unit 7.

In computing unit 7, calculations are performed according to expressions (3). (4), (5) and (b) depending on the type of measuring circuit and the unknown parameter. Codes proportional to the values of a known circuit element and an exemplary time interval are stored in the memory of computing unit 7.

The measurement time of an unknown element of the measuring circuit does not depend on the time constant of this circuit, but is determined mainly by the time of the analog-to-digital conversion of the ADC 6, as

ADC 6 can be used analog-to-digital converter of parallel type with output memory register,

As the computing unit 7 can be used micro-computers or a special, software-controlled, computing device.

Claims (1)

Claim A method for measuring electrical values of active resistance, inductance and capacitance, which consists in applying a DC voltage to a sequential active-capacitive or induction-active measuring circuit, one of the elements of which is known, characterized in that, in order to increase speed, exemplary time interval from the moment the direction was submitted. Rx = At With In U ₂ - U1 ~ ur ~ - for inductively active circuit. _ Ro A t ^{Lx =} - for active-capacitive circuit „At Lo in Rx U2-U1 Ui where Cx, Rx and Lx is the value of an unknown element of the measuring circuit; Ro, Co and U - the value of a known element of the measuring circuit; At is an exemplary time interval; th, U ₂ - the first and second instantaneous voltage values at the midpoint of the measuring circuit. Figure 2. Start