DD149422A1 - METHOD FOR MEASURING THE TIME RESISTANCE CHANGE - Google Patents

Abstract

The invention relates to a method for measuring the temporal change resistance, in particular in a lying in the circuit inductance-related resistor, which is arranged by a current branch of a bridge circuit via two coupling capacitors, while in the other parallel branch current the balancing elements are arranged. The aim and the object of the invention are to determine the temporal change in resistance of inductance-resisting resistors which are arranged in electric circuits by means of a suitable measuring method using a measuring bridge. This is achieved by feeding the measuring bridge with an alternating current whose frequency is chosen according to the requirements of the measurement to be taken and thus taking a differential voltage in the diagonal branch of the measuring bridge which is amplified and rectified and of which the absolute value is formed and integrated half-periodically , wherein between the half periods, the integrator quickly resets itself. Here, the dummy switching elements located in each bridge branch are tuned to resonance.

Description

Title of the invention

Ancestors for measuring temporal change

Field of application of the invention

The invention relates to a method for measuring the temporal change in resistance, in particular in the case of an inductance-sensitive resistor in the circuit, which is connected to one of the current circuits of a bridge circuit.

tion is arranged via two coupling capacitors, while in the other parallel branch current the balancing elements are arranged.

Characteristic of the known technical solutions

In the metrological detection of temporal V / ider - state changes of the current-carrying parts of electrical equipment that are in operation or short-term electrical or from the outside, e.g. As a result of switching operation, load or the like, difficulties arise when the measuring devices to be measured are subject to high inductance. One possible method of measuring the change in the resistance of inductance-resistive resistors is the direct measurement of current and voltage transients as well as the conversion into digital words and the subsequent storage of the digital values, with subsequent calculation in a corresponding relay system. Factors when programming b :: '. v. Calculation of the value can be taken into account and thus a realor Gegenbrundscrnnuf is determinable. disadvantageous in servant .Meßmethode is the considerable equipment expense and a greater amount of time for the required programming and for determining the influence factor.

Object of the invention

The aim of the invention is to determine the temporal change in resistance of electrical equipment that are connected to voltage, without much effort.

Dar Io now π of V / esens the invention

The invention is based on the object by means of a suitable measuring method using a measuring bridge, the temporal change of inductance-prone voids, which are arranged in circuits to determine. This is inventively achieved in that the measuring bridge is fed with a '.Vechsolstrom whose frequency is ger / ähit according to the requirements of the measurement and that thus in Diagonalste ig the measuring bridge a Difforenzspannung is removed, the amplified and rectified and of the absolute value is formed and integrated halbporiodcnweise, whereupon zv / ischon dan 'lalbporioden the integrator buckles back. The integral value changing from half wool to half wool is a measure of the change in resistance. Here, the reactive switching torques located in each bridge are tuned to resonance. The provision of the integrating light is triggered shortly before the next half-wool of the differential voltage by the rectified differential voltage. The resetting of the integrated circuit can also be effected by the sinusoidal current fed into the measuring bridge.

The advantage of the measuring method is that the course of the resistance value is displayed directly. The effort compared to the digital measuring method is low. By changing the supply voltage frequency, the sampling cycle can be easily adapted to the requirements of the measurement, whereby the frequency-boded deviation can be kept low. The use of a sinusoidal supply voltage makes it possible to quickly and easily estimate the frequency-related resistance deviation.

Outsourcing

The structure of the measuring circuit for performing the measuring method is in Pig. Λ shown. An AC voltage source feeds via the resistor R ₁ , which includes the internal resistance of the voltage source, into the bridge tone circuit. In the upper Zwo ig the measuring bridge of the transport stream i ^ _r durchflosscne and inductance-sensitive resistor R + r ('l) + £ u / L via the coupling capacitor C is connected. The Koppelkondcnsatoren C should doη greatly reduce the influence of the Transportstiomes on the measuring bridge and the subsequent measurement circuit. In addition, there is also a continuous inductance L,. arranged for resonance tuning in the upper branch.

In the lower branch of the measuring bridge, the balancing elements R and -L ₂ are arranged. At the two Widorstände R ^ the difference voltage AU. tapped.

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The calculation of Au is based on the quasi-stationary case, if the frequency of the measuring current is sufficiently large compared to the rate of change of the resistance.

The difference voltage ΛΗ is calculated as follows:

_sin

where / ⁼ г are & ^r C to.h -Q and to calculate from the switching elements of the measuring bridge а or b. The influence of the change in value A R = r (t) on the quantities a and b is the less, $ e smaller than R other resistances. Thus, for small A R ~ 0.1 (R _Q + R + R ^), a good linear dependence between Au. and AR can be achieved. The dummy control elements cause the phase shift 9, to be applied to the applied voltage. Boi Rosonansbgleich the two 2v; eige / | _ ₌ . _L ^) _{becomes the}

to vwC C. c- I /

V / ert b = 0, as well as T ^ ~ 0. The Rosonanz case has the advantage that a higher differential voltage Ak is available from the measuring bridge and increases the accuracy of the measurement.

The differential voltage Л, which is measured at the diagonal angle, is amplified and rectified. The differential amplifier 1 has such a large input resistance that practically no adulteration of AK can take place. The IntegrierGliGCL 4- has the task of converting the pulsating voltage from the rectification (absolute amplifier 2) into a signal that is as continuous as possible, which, as an approximately closed curve, reflects the temporal behavior, eg at the storage oscillograph.

The integration of one half-wave of the differential voltage is:

* i <9 =£ (йч (t) dt= (i)

Here, the phase shift ^ a is not taken into account, since only the half wool is integrated regardless of their phase position to the voltage e. The possible end value of the integration

2 AR

• yjä 7b ^{r r}

is practically not achieved or desired because it does not produce a sufficiently long constant signal.

It is ruled that ^the integrated value Ki is different by changing the integration constant Tt. As long as AU> U { , the integration W ₁ " _ло Uj _{30 takes place} . At the intersection AU -U '\ the integration is aborted and finally adjusts to the values Hii ··' Щг . "To obtain as long as possible, approximately horizontal line for visual observation" is

To choose such that the point of intersection U { = ΔU lies before Ali 's aximuin (for example, K ^ i), there is an initial deviation for an intersection, for example, at % ⁼ (Of ₁ ^ ^ / 23 of about б with respect to the subject.

The integration constant is calculated

where ty is the phase position of the intersection Ui = Дг <. The reset of the integrator is to be done so quickly before the next integration that they imint as little as possible from the end of the horizontal line we.

The signal is expediently removed after amplification and rectification because of the phase shift between the feeding voltage ѳ and the differential voltage ΔU, and supplied to a control 3 (· Ό) for the reset With the help of a threshold circuit and a Zoitglied the required Rückstellirapuls is provided.The integrated voltage frt is then fed to anzoigo-Registrleitvorrichtung 5 (ig · Ό supplied, eg a memory oszillografen.The bridge circuit is by the imaginable inductances Ln and Lp are each tuned to resonance in the branches Lashing resonant balance of the two bridge branches is connected in parallel with a voltage measuring device 6 dom resistor R. The differential voltage, is processed in differential amplifier 1 and then in absolute erstärker 2 rectified. In the subsequent integrator 4- (eg RC element), the absolute value of Ди. integrated half-periodwise. The reset of the integrator (eg by the fast discharge dos

Integration of the capacitor is done shortly before the start of a calf wave by appropriate wiring of the integrator 4. The control of the provision and the temporal classification is made by a controller that can derive their control signals in resonance from both the supply voltage e and the amplified and rectified differential voltage Лi , In case of detuning the Liess) back is the control signal expediently because of the occurring phase shift only from the differential voltage AU decrease. Before the I.Iessung of the resistance, the measuring bridge is adjusted. In the upper bridge, the Rosonanz case is set by switching the voltage measuring device б to the upper resistance R ^ and changing the inductance L ^ until the measuring device displays the maximum values. Thereafter, v / ith the Sparmungsmeßgerät 6 to the lower resistance R _x, and the lower connected Bräckenzweig using ₂ L of resonant tuned. Subsequently, the zero adjustment of & Ч is carried out by adjusting R in the lower bridge branch until the smallest signal on the display / recorder 5 (eg a storage oscillograph) can be seen.

The mode of operation of the measurement itself is shown in FIG. The resistance change R + r (t) results in an approximately equivalent differential voltage Au (t). This is done after the absolute amplifier 2 (shown in FIG. 1) to the pulsating DC voltage I Au '\ · 2i integration of / au' I, as shown in Fig. 2, with T {. Before every integration

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the integrator 4 (Fig. 1) is reset in the short time tg. The integrated voltage TiI is finally displayed on the display / recorder 5. If the oscilloscope used as the display and recorder is set appropriately, the vertical lines will appear less than the horizontal ones. If intervention is made by the controller 3 in the hello and blanking of the oscilloscope, then a better representation of 1 <i appears , which ultimately reflects the resistance curve as an approximately closed curve with a corresponding choice dos time scale.

The resonance damping of the measuring bridge has the advantage that the sensitivity of the .Meßbrücke is increased and simplifies the control for the reset signal.

For example, to alternating current or a pulsating direct current, which still acts on dio coupling capacitors C on the measuring bridge, almost completely eliminate the influences of the transport stream i ^ _T i, may be disposed in front of the differential amplifier 1, a filter. The choice of frequency for the current depends on the frequency of the transport current i ~ and the expected V / iderstandsverlauf.

Claims (1)

invention claim 1. A method for measuring the change in resistance over time, in particular in the case of an inductance-related resistor in the circuit, which in
the one branch of a bridge circuit over
two coupling condenseron is arranged while in
the other parallel current branch the balancing elements are arranged, characterized d a- du г с h, that of the sinusoidal differential voltage assumed in the diagonal branch, whose frequency depends on the l.Idssanf ordorations, the absolute value
is formed and integrated half-porodeweise, wherein between the calf periodon reset the integrator w _e d _e 2, method according to point 1, I η et
in that the blind-shutter solenoid ions (L, C) located in each bridge branch have been tuned to resonance. Method according to point 1 and 2, g e к η η η ζ e i с hnet characterized in that the resetting of the integrating iergliodes is triggered shortly before the next half-wave of the Difforenzspannung by the rectified differential voltage. 4, ancestors according to points Λ and 2, characterized in that the provision of the Integriorgliedcs -by the fed into the Lleßbrücko sinusoidal current. For this 3 pages drawings