DE1051386B - Electronically controlled motor counter with compensation circuit for direct current and currentless voltage integration - Google Patents

Description

GERMAN

The DC motor meters currently used have the following unfavorable properties: The voltage-speed characteristic is not linear, i.e. That is, the total angle of rotation is only proportional to a first approximation the current-time integral (charge) or the voltage-time integral. Particularly large deviations of the linearity occur at the beginning of the characteristic curve (start-up limit) and at very high speeds. This is also achievable in the middle area of the characteristic curve, the actual working area of the motor counter Accuracy not very great. The usable work area usually only extends over a power of ten. In addition, the speed is still dependent on the power consumed, and it must as a result, a change in the characteristic curve as a function of time, load and temperature is expected will. Since the classic motor meter consumes more electricity, it can be used for Voltage integration can only be used if the internal resistance of the voltage source is low and has too much self-consumption to measure high voltages.

A whole series of endeavors have become known which aimed at the ones listed here To eliminate the error of the classic motor counter, in most cases an attempt was made by Changes of a mechanical nature to the motor driving the counter affect the properties of this To change the motor so that useful results could be obtained with the motor counter. By however, in all of these attempts only minor improvements have been made, for the main part therein exist that the linearity of the speed-voltage characteristic improves somewhat in the middle working range and the start-up limit has been lowered somewhat. The real sources of error, dependency the speed of the consumed power, pre-band being a start-up limit, too small usable The work area and excessive power consumption were not eliminated and were able to open This way, they cannot be eliminated either, since every DC motor reduces the meter quality Must have natural properties.

Since with the classic motor meter the integration of very small currents due to the too large Power consumption of the motors used, which is due to the need to drive the counter Performance cannot be reduced at will, is not feasible at all, yeasts other endeavors in addition, by connecting an electronic current amplifier in front of the motor counter the To make integration of very small currents possible. Such devices, which have been known for a long time, naturally all have sources of error caused by the electronically controlled motor counter

with compensation circuit

for direct current and currentless

Voltage integration

Applicant:

Dipl.-Phys. Dr. Walter Walisch,
Scheidt / Saar, Eichendorffstr. 18th

Dipl.-Phys. Dr. Walter Walisch, Scheidt / Saar _r
has been named as the inventor

Motor counters are conditional, and require a very high device-wise for the current amplifier Expenditure.

From other areas of measurement technology, on the other hand, methods and apparatus are known which allow z. B. currents, voltages, resistances or the ratio of currents or voltages very precisely to determine that the variable to be measured in a bridge or compensation circuit with a very precisely adjustable comparison variable is compared, and that the adjustable variable of Manually or by a servo mechanism until the bridge equilibrium is reached is.

The invention is based on the knowledge that with a driven directly or via an amplifier Motor counter the natural errors can not be eliminated and that essential Improvements can only be achieved by using a compensation method. A suitable one There is a comparison element because there are DC voltage generators with strictly linear speed-voltage characteristics gives. The invention focused on an electronically controlled motor counter Direct current and currentless voltage integration refers, is that one of the to be integrated Size proportional voltage of the voltage of a linear speed-voltage characteristic curve DC voltage generator is connected in opposition and the resulting differential voltage amplifies one with its generator mechanically rigidly coupled direct current motor is supplied so that a change the size to be integrated such a

809 767/217

3 4

Change in the speed of the motor and thus also required a rigid coupling that produces an exact proportionality of the generator that the nality of the generator is between Qq and Ω ^, and the following applies:
output voltage strives to reduce _{the Q = m = U {i} _ _{g) fb and Q = Q / d = u {i ) / w>} differential voltage at the amplifier and '
that the total angle of rotation of the motor or generator 5 The angular speeds of the generator and shaft serves as a measure for the size sought. The motor axis are therefore strictly proportional to the voltage U. output of the converter output at the output of the converter. If the converter guarantees a strict pro-The variable X to be integrated is at the input of the portionality between the measured variable X and the current converter A, the nature of which depends on the type of voltage U emitted - this condition and the order of magnitude of the voltage to be integrated can be included Current and voltage integration practical size - in the case of current integration z. B. Realize a table with any accuracy and with differently dimensioned measured quantities corresponding to the circumstances usually with sufficient resistance of sufficient load capacity and accuracy - then the following applies:
Temperature constancy for this purpose - determined 15 Q _a = cX (le) / b and Q _M = cX (ls) / bd.
will. At the output of the converter one of the to

integrating variable X exactly proportional equal. Accordingly, the voltage U = cX is emitted in the state of equilibrium. The proportionality angular velocities of the motor and generator factor between U and X is c. One pole of the axis is exactly proportional to the respective value of the measured variable X output terminals for the voltage U , and the total angle of rotation of each axis at the input of the amplifier S. The other pole is between two times is the integral of the measured variable over the winding of the generator G is exactly proportional to the distance between these times when the stronger B is connected. If the changes in the measured variable taken from the generator take place so slowly that the given voltage E is applied to the amplifier, the arrangement is practically always in the equation U + B or U - B. The amplifier has 25 weight status.

the \ ^r erstärkungsfaktor k, it is at its initial state of equilibrium is retained even when the voltage V behaves gear Ti = (U + E) cast. The nismäßig rapid changes in the measurable variable always voltage V is on the winding of the motor M, set because any deviation from the equilibrium of its axis directly or via a gear rigid with state momentary is connected to the gain factor k of the axis of the generator, so that the 30 increased change in the voltage V applied to the motor winding angular speed Qq of the generator axis pro, which axis is proportional to the angular speed Ω μ of the motor deviation from the equilibrium state. If the polarity is correct, the aim is to make.

Motor and generator windings are connected to the amplifier The input resistance of the integrator is practically the voltage U - B , and the following table is identical to the input resistance of the warping (if the polarity is incorrect, U + E is connected to the amplifier and can therefore be by using stronger and the arrangement begins to oscillate): make corresponding electron tubes very large, jj _ y - .. ■ so that both very small currents and very large ones

", _. . . _ -,., Voltages without significant loss of performance

E = bQ _G with 6 = proportional seam factor ^ _{can be integrated} _

between h and U ₀ . The load on the motor or generator axis that

V = k (UE). Quality of the speed-voltage characteristic of the

Q _M = aV with a = motor proportionality factor and changes in the gain factor

between V and Ωμ only affect the correction term ε and

Q ₀ = dQ _M with i = proportionality factor ⁴⁵ £ ^abe * therefore no influence on the measured

between Q ₀ and Q ₁₁ . Result, so that the arrangement is arbitrarily large

Can deliver services and that changes in the

In equilibrium, the following applies: the power output does not cause any errors

Ε = ΙΩ _α = ΙαΩ _Μ = αΒαν = ώα1 _ί (υ-Ε). ^k · ° ^{can the} quality of the amplifier is next to

■ ^{M v} ' 5 ° neuter.

From this it can be calculated: There is no start-up limit because the generator

2? _ υ / η λ. l / aiidJi) t> ^e i the angular velocity zero no tension

- gives up.

. With abdk > 1, this case can be achieved by The achievable accuracy is entirely by

A sufficiently large gain factor k and due to the quality of the speed-voltage characteristic curve of the

appropriate choice of the other proportionality factors determined by the DC voltage generator,

Realize very easily, will: The invention is based on the following from

i / a & dA = _e «l, tmdes applies: B = t7 (le). management example, which includes all the previous

Settlement fulfilled to a sufficient extent, closer

The generator voltage E is therefore refined by 60 alone:

U determined, and changes in the various A power supply, consisting of a mains transformer, proportionality factors have practically no one-way rectifier and filter elements, supplies the direct current required to determine the value of E. drive of the amplifier and, on the other hand, there is an alternating voltage as required. The first amplifier stage consists of exact proportionality between the powerless 65 from a double triode (e.g. ECC 83), its cathode picked up generator voltage £ and the angular speed Qq of the generator axis together via a cathode resistor (e.g. IkQ) - this to the earthed negative pole of the In the power supply, strict proportionality is carried out by many DC-generated DC voltage, and their voltage generators are guaranteed under the operating anode conditions via an anode resistor (e.g. 40OkΩ) - as well as because of the

Claims (3)

50 kiJ), the variable center tap of which is connected to the positive pole of the DC voltage generated in the power supply unit, the anode voltage. The anodes of the double triode are also connected to the control grids of two 5 steep end pentodes (e.g. EL 84) via grid leakage resistors (e.g. 200kΩ), the cathodes of which are connected and grounded via a cathode resistor (e.g. 2kΩ). The screen grids of the two pentodes are directly connected to the anode voltage, the anodes via load resistors (e.g. 4 kΩ). The output voltage of the amplifier, i.e. That is, the voltage between the two anodes of the pentodes is applied to one winding of a small DC motor (e.g. servo motor) with two separate windings. The second winding serves as a generator winding and emits a DC voltage that is precisely proportional to the speed of the motor. The axis of the motor is connected to the counter via a switchable gear. No special requirements are placed on the counter, as the power output by the motor has no influence on the speed, so that it is also possible to convert the rotary movement of the motor into a linear displacement (e.g. paper feed of a recorder or pointer position of a recorder) to transform without sacrificing accuracy. A capacitor (e.g. Ο, ΙμΡ) is located parallel to the generator winding, which somewhat smooths the undulating DC voltage emitted at low speed. One pole of the generator is connected to a grid of the double triode via a grid leakage resistor (e.g. 50 kΩ). The other grid of the double triode is grounded via a grid leakage resistor. The second pole of the generator is connected via a protective resistor to a pole of the voltage proportional to the variable to be integrated, the second pole of which is grounded and is also via a capacitor (e.g. 0.5 \ iF), which somewhat buffers steep changes in the measured variable , grounded. To integrate the current, the current is allowed to flow through a temperature-independent resistor of known magnitude and the voltage drop that occurs across this resistor is integrated. Since the resistance can be made as large as desired, currents of 1 microampere can still be integrated with sufficient accuracy in this way. Several resistors of different sizes are built into the arrangement so that currents in a range of 9 powers of ten (with an accuracy of ± 0.1%) can be integrated with one device. To integrate very small voltages of the order of mV, the voltage is transformed with the aid of a compensation amplifier or a fully automatic registration potentiometer. B. by controlling a linear auxiliary potentiometer with the writing device of such a registration potentiometer - into a proportional larger voltage and integrates this amplified voltage with the arrangement according to the invention. Any measured variables which can be transformed into a voltage proportional to the measured variable with the aid of a linear potentiometer, at the ends of which a constant voltage is applied, or another device, can be integrated with the arrangement according to the invention. The arrangement according to the invention can be used particularly well for measuring the charge in direct or indirect coulometric titrations. The electrolysis current is advantageously allowed to flow through a resistor dimensioned in such a way that the integral of the voltage drop measured by the arrangement according to the invention, which is generated by the electrolysis current across this resistor, changes the position of the counter coupled to the "motor generator" so that the concentration the substance to be integrated or its number of moles can be read off immediately. If the variable to be integrated is already shown graphically, the integral sought can easily be determined by having a fully automatic light pointer follower follow the curve. The light pointer follower is coupled to a linear potentiometer at the ends of which a constant voltage is applied. Accordingly, the voltage tapped at the center tap of this potentiometer is proportional to the measured variable, and the integral of the original measured variable, i.e. H. determine the area under the curve presented by determining the integral of the voltage output by the potentiometer with the arrangement according to the invention. With the high value of the gain factor achieved in the arrangement according to the invention (about 1000), the excellent linearity of the speed-voltage characteristic curve of the generator (deviations are less than 0.1%) and the short response time of the motor and its winding caused by the circuit is iron-free and already has a very small moment of inertia, the motor counter according to the invention can be used to achieve such great accuracies, both in the integration of short-term pulses and in the integration of slowly changing measured variables, that errors can no longer be detected with the usual control measuring methods. Patent claims: 1. Electronically controlled motor counter for direct current and currentless voltage integration, characterized in that one of the to integrating quantity proportional voltage of the voltage of a linear speed-voltage characteristic curve having DC voltage generator and the resulting differential voltage amplified is fed to a DC motor mechanically rigidly coupled to the generator in such a way that a change in the Size such a change in the speed of the engine and thus also of the generator causes the voltage delivered by the generator to match the voltage at the amplifier The aim is to reduce the differential voltage and that the total angle of rotation of the motor or generator shaft serves as a measure of the size being sought. 2. Arrangement according to claim 1, characterized in that the achieved in the amplifier Voltage gain is chosen so large that changes in this gain and deviations on the linearity of the speed-voltage characteristic: of the DC motor used as well as changes in these characteristics during operation, e.g. B. by changes in the engine mechanically delivered power, does not affect the speed of the rigid with the engine coupled generator, so that the speed of both depends exclusively on the one to be integrated Size depends. 3. Arrangement according to claim 1 and 2, characterized in that the motor and generator of