DE1281160B - Electrical circuit arrangement for follow-up controls - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. α .:

GOId

German class: 42 d-5

Number: 1 281160

File number: P 12 81 160.8-52 (M 66249)

Filing date: August 6, 1965

Opening day: October 24, 1968

The invention relates to an electrical circuit arrangement for follow-up controls with the help of an input circuit depending on the physical quantity to be measured DC voltage is generated. Such circuits are z. B. with so-called compensation recorders and also used in large display instruments.

With conventional recorders, the setting time for the indicating or writing organ is through the respective construction and dimensions are usually practically fixed, d. h., a A certain response time required for special applications can only be achieved during the manufacture of the Schreiber must be taken into account. However, the setting time essentially determines the quality of a Registration diagram. Depending on the application, there is often a very short setting time to detect Peaks or a very long response time for averaging are desirable. This requirement of practice has so far been neglected by writers. Many registration charts are near useless, simply because instead of a registration line there is a hopeless hatching on the diagram or because a registration that is much too sluggish does not follow a rapidly changing measured variable could.

The invention is therefore based on the object of providing a follow-up control, in particular for compensation recorders, to be improved in such a way that the setting time is freely selectable and that it is preferred can be set during operation in such a way that it is optimal for the respective measuring task is. A change range of the response time in the ratio 1: 2 is not sufficient here, but with The aim of the invention is to continuously set the response time in a range of about 1:10 can.

This task is achieved with an electrical circuit arrangement of the type described at the beginning solved according to the invention by the use of a limiter circuit, which is to be measured by the physical variable dependent DC voltage is limited to adjustable values, and thus, that the difference between this limited voltage and a speed-proportional generator voltage in a manner known per se via a null amplifier that is coupled to the generator Follower motor is supplied.

The null amplifier is expediently subdivided into two sub-amplifiers, the voltage difference being derived from the DC-electrical circuit arrangement proportional to the measured variable for
Follow-up controls

Applicant:

Metrawatt Aktiengesellschaft,

Electrical measuring equipment factory,

8500 Nuremberg, Schoppershofstr. 50-54

Named as inventor:

Johannes Brenner,

Fritz Puschban, 8500 Nuremberg

voltage and the equivalent voltage to the first Sub-amplifier is supplied. At the exit of the

The adjustable limiter circuit is located in the first sub-amplifier.

According to a further embodiment of the invention, the limiter circuit is derived from the series circuit two anti-parallel connected diodes and a potentiometer. It is special advantageous if the adjustment member for the potentiometer of the limiter circuit directly from the front or after opening the housing door of the display or Writing device is easily accessible.

Details of the invention are given below with reference to an exemplary embodiment and in the drawing explained in more detail. It shows

F i g. 1 is a block diagram of a follow-up control for recording a measured variable in which the limiter circuit is used according to the invention, F i g. 2 shows a diagram of the output voltage of the limiter circuit as a function of the input voltage of the first sub-amplifier with different settings of a resistor and

F i g. 3 Details of the limiter circuit.

According to FIG. 1, the physical quantity M _x to be measured is stored in a transducer 10, ζ. Β. a so-called transmitter, converted into a direct voltage U _x proportional to the measured variable. With the compensation device 9, a variable comparison voltage U _{v is} generated, which is the opposite of the voltage U _x. The compensation device 9 can be formed, for example, from a bridge circuit that is fed by a constant current source. A measuring potentiometer on which a wiper operated by the follower motor can be moved is connected to the bridge circuit, see above

809 628/1460

1 281 16Ö

that a comparison voltage U _v dependent on the position of the potentiometer wiper is obtained from the bridge. The difference U _el = U _x -U _v is fed to the limiter circuit 1 either directly or via a first sub- amplifier 2 b, depending on the dimensioning. The limited voltage U _b arrives at the input of the zero amplifier la, at the output of which is the follow-up motor 4, which adjusts the wiper of the measuring potentiometer until the difference delay U _{et has} become zero. Thus, the position of the potentiometer wiper is a measure for the voltage U _x or for the measured variable M _x . In order to avoid overshoots at the adjustment point and to achieve an adaptable dynamic behavior, a voltage U ₁ . fed back from generator 3 to the input of amplifier la .

As a servomotor 4, a directional force-releasing moving-coil measuring mechanism is used, which is robust and hardly ever A brushless DC motor with excellent efficiency is subject to wear. The moving part of the measuring mechanism carries on the one hand the pointer and / or the writing device of the Display device 5 and, on the other hand, influences the compensation device 9 in the sense of a compensation sation of the measurand.

To get the speed-dependent feedback voltage U ₁ . To obtain, a second moving coil winding j ■, preferably on the same measuring mechanism frame, is attached to the measuring mechanism axis in addition to the display and writing device.

As in Fig. 3 illustrates, there is a limiter 1 from the two anti-parallel connected diodes Ga and 6 b and the to in series potentiometer 7. This series circuit limits-the output voltage of the first amplifier stage Ib, or in his absence the voltage U _ix of the input circuit 8. The height the limited voltage can be adjusted with the potentiometer 7. In order to be able to adapt the setting time easily at any time, even with the measuring device installed and in operation, the control button of the potentiometer 7 is arranged so that it is easily accessible either from the front of the housing or after opening the housing door is.

In the in Fi g. The diagram shown in FIG. 2 shows the output voltage U _{b of} the limiter circuit 1 as a function of the one-step voltage U _e j of the amplifier 2 b for different positions or resistance values of the potentiometer 7. For the input voltage E / _B - ₂ at the amplifier la applies

For a certain desired response time, let the angular speed of the close-up motor be ω. In order to give the motor this speed, a voltage UJ _{2 is} required at the input of the second sub-amplifier 2a. The feedback voltage of the generator 3 occurring at this speed is ET /. The limited voltage required for this setting time and to be set on the potentiometer 7 is thus obtained

Vi = VU + Vi. _6s

This means that the response time of the measuring system can be set within an upper and lower limit value can be changed continuously with the potentiometer 7.

B ° ei of the maximum angular velocity, that is at the shortest one part-time, the amplifier 2 is a full scale, ie

U _e2 = U _{e 2 max} and U _r = U ₁ . _max .

The output voltage of the limiter circuit must in this case

"Λ mn ν * - '/

^} b max

e 2 max

U _T

, _{i.e. A 7 can be set} to the maximum value R _imax . The unlimited output voltage of the amplifier 2 δ (R ₇ = oo) must be greater than U _bmax . The threshold voltage U _{e 2 min} , that is to say the input voltage of 2 a at which the ServdMechäüis'-mus is just starting, determines the smallest possible angular speed, that is, the largest setting time. This results in the smallest tension

Vf, min = \ Ue 2 min

The knee tension of the diodes 6 a and 6 b fulfills these conditions.

Since the proportional range of the entire amplifier is only about 1% of the length of the scale, is the desired angular velocity practically constant over the entire scale.

Claims (9)

Patent claims: 1. Electrical Sehältüngsähordflüng for sewing controls, in particular for Kompensätionsschreibef, in which with the help of 6iher input circuit depending on the physical quantity to be measured elile DC voltage is generated, characterized by the "application of a limiter (1), which depends on the physical quantity to be measured DC voltage (U _et ) limited to adjustable values (U _b ) , and in that the difference (U _e2 ) from this limited voltage (U _b ) and a speed-proportional generator voltage (Ü _r ) iii is known per se via a zero amplifier (2 a ) is fed to the next mofoof (4) coupled to the generator (3). 2. Circuit arrangement according to claim 1, characterized in that the Nüllverstäfker is divided into two sub-amplifiers (2ö, 2b) . 3. Circuit arrangement according to claim 1, characterized in that the limiting circuit (1) is formed by the series connection of two anti-parallel connected diodes (Sä, 6b) and a potentiometer (7). 4. Circuit arrangement according to claim 1, characterized in that the follow-up motor (4) is formed by an approximately Richtkräftlöseh moving coil measuring mechanism and the generator (3) delivering the speed-dependent Rückführspanmmg (U _1. ) Of a fine second winding applied to the frame of the moving coil measuring mechanism. 5. Circuit arrangement according to claim 1 or 2, characterized in that the input circuit (8) has a Spännüngs- or '. Contains current compensation circuit (9), the output value (t / ") of which is changed by the following motor (4) in the sense of a compensation of the measured variable (V _x ) . 6. Circuit arrangement according to claim 5, characterized in that a _{bridge circuit fed by a constant current} source (J cons t) is used as the compensation circuit (9), in which a potentiometer wiper forming a bridge diagonal point is adjustable by the movable part of the follower motor (4). 7. Circuit arrangement according to claim 5, characterized in that the compensation voltage (U _v ) is generated with the aid of a Hall generator attached to the movable part of the measuring mechanism (4) and movable in a permanent magnetic field of steadily decreasing induction. 8. Circuit arrangement according to one of claims 1 to 7, characterized by its Use on compensation indicators or recorders. 9. Circuit arrangement according to one of claims 1 to 8, characterized in that the Adjustment element for the potentiometer (7) of the limiter circuit (1) directly from the front or after opening the housing door of the display or Writing instrument accessible and easily adjustable is. Considered publications:
Grave: Electrical measurement of non-electrical quantities (1962), pp. 68 and 69; Meinhe — Gundlach: Paperback of the High frequency technology, 2nd edition (1967), pp. 1194 to 1198. 1 sheet of drawings