DE1463155A1 - DC compensation circuits with motorized self-adjustment and digital position indicator - Google Patents

Description

Direct current compensation circuits with motorized self-adjustment and digital position indicator The general principle circuit of a direct current compensation circuit or direct current bridge circuit for the transmission of an analog position value is shown in Figure 1.

The analog position value is determined by the slider position of the encoder potentiometer GP formed. If there is a misalignment between the slider position of the encoder potentiometer GP and. of the receiver potentiometer EP, the.?epvomotor-MQ moves the slider of the letäsren until the zero indicator J, which an amplifier V to generate the power required by the servomotor M & is connected downstream, no more voltage is, and thus balanced the DC compensation circuit or bridge is. This is the analog position value of the grinder from GP to the grinder transferred from EP. He can move on a scale and with the grinder can be read from the EP coupled pointer. A 'highly sensitive' indicator can be used as a zero indicator Galvanometer, a null amplifier, or a bipolar relay can be used.

The required between the angular travel of the wiper and the motor rotor (ibersetzung is achieved by an appropriate transmission.

The DC voltage compensator works in a similar way. With him the measuring voltage takes the place of the transmitter potentiometer. The compensation potentiometer, whose slider position is proportional to the measured value is determined by a constant Auxiliary voltage fed in.

In many cases, the digital representation of the displayed position or measured value desired. This can be done with various methods and circuits, as they came to be known in the last few years: 1.) Most digital voltmeters are essentially based on a short-term integral of the measuring or position value that is constantly being recreated. You can call them dynamic Denote procedure.

2.) Other digital voltmeters use decadal structures Step compensators for implementation.

3.) The disk encryptor is as a pure position setter as View static procedure.

4.) The radial slotted scanning disc that moves with the a pointer or potentiometer wiper is in its essence an integrator. By moving the disc up to the appropriate angular position generated light pulses or the like. Are summed up in a counter and displayed. A suitable directional discriminator takes care of the subtraction of the impulses that triggered by the backward movement of the disc.

The common disadvantage of the first 3 procedures, their relatively large technical effort, the 4th example cited method for implementation an analog position or. Avoided measured value in a digital one.

The advantage of this procedure, which is inferior to the others There is a technical effort, the disadvantage is that in certain periods of time a repositioning or zeroing must be carried out, since even with one, her short-term Disturbance, e.g. B. power failure, all of the following position values are implemented incorrectly.

never the invention underlying task has to Target, Reliable positioning with extremely little effort, especially with the advantages of the static process (springtime reproducibility). never The demands placed on accuracy should be those of a good compensator come close with approx. 1 ... 2% o. This object is achieved by a circuit which shown in Figure 2 as an example of a position transfer with digital display is.

The from the neber potentiometer GP to the receiver potentiometer 'EP The angular position to be transmitted is again carried out by comparing the voltage between the two Slider settings using a blull indicator J. This can be a zero voltage amplifier, as well as an ITullspannungs-Reäis, z. B. a bistable electronic relay. The zero voltage is amplified by a subsequent amplifier with modulator VM and chopped by means of a pulse generator G or into pulses of the same amplitude converted. The pulse frequency is determined by the pulse generator, its polarity is determined by the Indicator determined. These impulses are now upper in a manner known per se an electronic switch S, which is generally a bistable multivibrator and usually a Schmitt trigger for steepening the pulse edges and for generating them contains a constant pulse amplitude, a stepping motor M supplied. The Schmitt triager Can be omitted if a bistable electronic relay is used as the zero indicator J a Schmitt-Triaeer is used. Used as indicator J, a constant voltage amplifier with a modulator, for example a Trans istor chopper amplifier, then used The modulator VM can be saved if the chopper frequency is adjusted accordingly the step frequency of the stepping motor M and the circuit of the amplifier is designed so that the Zerhaeker frequency is not suppressed. The step motor M is coupled to the receiver potentiometer EP via a corresponding gear and at the same time drives a roller counter Z, which can be moved in both directions is. On the roller counter Z, its digital display of the analog grinder position of EP is always proportional, the result is the completely synchronous one, in small Step-resolved mapping of the slider movement of EP in the sense of a static Position encoder. Each step of the motor M increases or decreases the displayed one Numerical value by one unit.

The gear ratio selected between the stepper motor M and the receiver potentiometer EP depends on the angular range of the potentiometer and on the size of the step of the motor M. The setting speed of the position transmission depends from the times: step frequency of the motor and from the required ten Gehtuigkelt. _ The fZusa mtenhang results from the relationships: Total number of steps: S and _ ges " Response time: T = e # _ F S AF S times times Here are: aF / F = percentage error and Smax = maximum number of motor steps / second Instead of the transmitter potentiometer GP and the receiver potentiometer EP, other resistance transmitters or receivers can of course also be used, e.g. B. Step regulator or punch card setpoint systems. In all cases, however, it should be noted that the step size on the potentiometer or step controller or the like is selected to be smaller than the step size of the motor. If this is not the case, the system does not come to rest. It starts to commute.

If you also want to display the position value in analog form, then you can a pointer ZE movable over a scale SK via a corresponding gear couple with the rotor axis of the stepper motor M.

Conversely, of course, the scale can also be coupled with the stepper motor and the pointer can be fixed. A circuit example for one after the The same principle working motor compensator is shown in Figure 3.

The circuit corresponds to that in Figure 2, but the zero voltage occurs here not as the difference between two slider positions, but as the difference between the measuring voltage UM and the part tapped by the wiper of the potentiometer R the auxiliary voltage 'U, on.

In this circuit, too, the unambiguous assignment of the digital display to the respective position of the wiper of R 0 is guaranteed - the additional analog display takes place in the same way.

Of course, the potentiometer Ro can also be controlled by a step regulator or the like. Be replaced.

The subject matter of the invention thus relates to all motorized subsequent comparison, bridge and compensation circuits, which are used as common Feature a stepper motor controlled by the zero indicator via a modulator, on the one hand with a comparison potentiometer, step regulator or the like. On the other hand is mechanically coupled with a roller counter or the like, whereby in principle a closed transmission or control system is formed. The solution of tasks position transmission with stepper motors using open transmission systems is described in a report by W. Neubert and F. Wildermuth. A demarcation of the present application against the use of stepper motors in open transmission systems is therefore required.

Practical application examples: motor expansion joints, systems for position transmission, Bridge circuits, in particular resistance measuring bridges.

An additional remote display of the digital or analog Output value is possible by one or more rere additional stepper motors on 4m e electronic switch terp (, which must be designed accordingly for this purpose. Since the assignment of the positions of the rotors to the stepper motor If it is unambiguous, the display value can be transmitted to impulse lines over many kilometers. The particular advantage of this transmission of a measured value is that its susceptibility to interference is extremely low and the influence of the line resistances - even in the case of strong temperature changes - is practically zero. Of course, you can also assign an electronic switch to each stepper motor.

In this case, the modulator VM must be designed accordingly. Intended to the digital value appear printed, then instead of the roller counter with a counter with printable types coupled to the stepper motor. The imprint of the Digital values can be used in a manner known per se, e.g. B. by pressing paper and ribbon.

If the stepper motor is designed for a correspondingly high output, then the circuit can also be used for closed-loop control. In this case, the stepping motor is a servomotor that drives an actuator, such as a valve or the like. The power supplied to the stepper motor must be taken from the electronic switch, which in this case must be dimensioned accordingly. Literature: W .. Neubert and E. Wildermuth: A forward and backward rotating stepper motor for high step frequencies and a pulse walker for constant pulse duration independent of the pulse frequency.

Feinwerktechnik, issue 12, December 1961.

Claims (1)

P ate not, cont ü che 1.) DC compensation, bridge or comparison circuit with motorized self-tuning and digital display of the angular position of a Potentiometerschleifers, characterized in that the zero voltage, for example, of two as the difference between the slider voltage potentiometer (GP and EP), step regulator or the like, or as a difference between the measuring voltage (UM) and the wiper of the potentiometer (R0), a step regulator or the like electrical zero voltage relay and is modulated in a preferably amplifying modAator (VM) with the pulse voltage of a generator, preferably astable multivibrator, and a stepper motor (M) is fed via a suitable, preferably electronic switch, the rotor of which is connected to the potentiometer wiper (EP or $ o), preferably ü Mechanically coupled via a gearbox, as well as with a roller counter or the like that can move in both directions, 2.) Circuit according to claim 1, characterized in that an additional analog display of the measured or position value is provided by the mechanical coupling of the rotor of the stepper motor ( M) with the pointer (ZE) that can be moved over a fixed scale (SK) or with the scale or the like that can be moved over a fixed scale (SK), preferably via a gear. 3.) Circuit according to claim 1 and 2, characterized in that the Modulator.VM can be omitted if a mull voltage amplifier with modulator, preferably a transistor chopper amplifier, is used as the indicator (J), in which the modulation frequency is not suppressed and the step frequency of the Stepper motor (M) is adapted. 4.) Circuit according to AnNrueh 1 - 3, characterized in that a counter provided with printable types is mechanically coupled to the stepper motor (M) to print the digital value instead of the Rollenzah.lwerkes (Z). 5.) Circuit according to claim 1 to 3, characterized in that for additional digital or analog remote display of the measured or position value one or more additional stepper motors are connected to the electronic switch, which must be designed accordingly are preferably mechanically coupled via a gearbox with a roller counter movable in both directions, preferably via a gearbox, -with a pointer movable over a fixed scale SK or with a scale movable over a fixed pointer or the like. 6. Circuit according to Claims 1-3 and 5, characterized in that the stepper motor (M) can also be used as a servomotor for control systems if it is designed with an appropriate output.