DD281101A7 - METHOD OF MEASUREMENT OF VALUE BY PULSE WIDTH MODULATION - Google Patents

Abstract

Pulse width modulation method refers to the cable manufacturing industry, especially to extruder lines, stranding machines and rewinding devices for quality determining measurement and control of the tensile force in the continuous manufacturing process and thus for targeted reduction of the production of comminuted material under operating conditions. According to the invention, this method is realized by making use of the meszwertabhaengigen differentiation of rectangular pulses of fixed frequencies. A subsequent trigger converts the positively differentiated pulses such that a narrow square pulse is generated at a zero mz value and a broad pulse at a maximum mz value. These pulses are transmitted, processed and displayed. The method involves introducing signed sample values into capacitive and / or resistance transducers for further processing for display purposes, such that each transducer portion effects an internal differentiation component and thus provides its own contribution to the output pulse width. Fig. 1 {Meszwertgewinnung; Pulse width modulation; Extrusion lines; stranding; Measurement; Regulation; Traction; Differentiation; Rectangular pulses; capacitive resistance converters; Display; Output pulse width}

Description

For this 3 pages drawing

Field of application of the invention

The invention finds in the measurement technique for obtaining measured variables everywhere where a measured variable can be converted into a capacity size, especially in the cable manufacturing industry, Extruderanlagon and stranding machines for quality-determining measurement and control of the tensile force in the continuous manufacturing process and thus for the targeted reduction of Committee production of sensible material, such as optical fibers.

Characteristic of the known state of the art

According to a method described by Seidel, H. H .: Microcomputer Compatible Capacitive Sensor System - In: Wiss.Z. the Technical University Karl Marx City 27 (1985) H4. - S.553 for data acquisition by means of pulse width modulation operates on the principle of the pulse loading method, wherein a capacitor, which is usually designed as a capacitive transducer is charged via a reference source and is discharged periodically via an electronic switching unit. The pulse width is generated by a downstream trigger. The internal transfer processes take place in the frequency range up to a few MHz.

Disadvantageous in these designs are parasitic measuring effects, which are usually only to be eliminated by special transducer designs, which in turn require a higher circuit complexity.

As a further critical Systbmelemente the electronic switches are to be regarded with their offset sizes and their drift behavior. In addition to the drift of component parameters, the temperature drift of the operating voltage and refurence sources used must be taken into account. Not least also as a result of the relatively high component cost, this process for betriebsmeßtochnische concerns appears to prone to interference.

7.Ie of the invention

It is an object of the invention to achieve with a capacitive transducer by a simple method for obtaining a value measurable by the human or a computer and afflicted with high resolution measurement result.

Explanation of the essence of the invention

The invention has for its object to provide a way by means of a method to transform the capacitance value of a capacitive transducer with a high resolution and good linearity in a digital and / or analog measurement. The method should work stably and easily under operating measurement conditions.

According to the invention the object is achieved in that a measured variable is converted in a known manner in a capacitive transducer into a capacitance value and the capacitive transducer is connected to a square wave generator. The square-wave voltage of this generator is converted by the combination of the capacitor of the capacitive transducer with the resistor and the downstream trigger in a pulse width modulated form. The pulse width forms the

Measured value. This pulse width-modulated square-wave voltage will now be subjected to a measured value processing and then a Display unit supplied. It is according to the invention that the capacitive converter is composed of two parts, so that in a corresponding A value addition or subtraction (difference) of the measured values takes place (FIG. 2). In addition, according to the invention, that the measured value does not act on the capacitor, but on the resistance, wherein the Capacitor is replaced by a fixed capacitor (Fig. 3). Furthermore, the invention is that a measured variable to a capacitive transducer and a second to a Viderstandswandler act, depending on the direction of action an addition or a subtraction (difference, Compensation) takes place (Fig. 4). embodiment The invention will be explained in more detail with reference to the embodiment shown in the drawing Fig. 1. In a specific application, it is assumed that the measured variable 1 is a converted tensile force, the on a Force measuring device, i. a capacitive transducer (plate capacitor) 2 acts, wherein in this capacitive transducer. 2

only one of the two plates is subjected to the tensile force.

This movable plate of the capacitive converter (plate capacitor) 2 is connected to the output of a rectangular generator 3

connected, which consists in the simplest case of a single wired gate. The fixed part of the capacitive

Converter (plate capacitor) 2 is connected via a resistor 4 to the ground potential, so that the combination of

capacitive transducer 2 and resistor 4 acts on the rectangular pulses of the rectangular generator 3 so differentiating thatmeßwertabhängige differentiation levels of the square waves at the input of a threshold circuit 5 are effective. In the simplest case, this threshold value circuit 5 can be realized by a single gate with trigger behavior. At the

Output of this trigger 5 are measurement value dependent pulse width modulated rectangular pulses available, these pulses

are further processed in a measured value processing β by means of digital counting methods and displayed on a display 7. There is also the possibility of the pulse width modulated square pulses within the

Meßwertverarbeitung 6 by a low-pass filter in a measuring variable proportional DC voltage for the purpose of analog To convert signal processing. Dio specific advantages of this method are that the capacitive transducer (plate capacitor) 2, the Rectangular generator 3, the resistor 4 and the threshold circuit 5 to a kompaktan module as an active sensor. 8

let summarize, so that the electronic conversion of the measured variable 1, the converted tensile force, directly to the

Place of origin can take place. The connection from this active sensor 8 to Meßwertverarbeitung 6 can by Line connection 9 occur because Rectangular pulse sequences are transmitted, the easy for simple adaptation measures

are regenerable.

It is also anzuseilen advantage that in the active sensor 8 an analog Meßgrößenabbildung exclusively below Use of digital, active components takes place.

Claims (5)

1. A method for data acquisition by means of pulse width modulation, characterized in that a measured variable (1) to a capacitive transducer (plate capacitor) (2) with a resistor (4) a variable differentiating element between a square wave generator (3) and a threshold circuit (a trigger ) (5) forms, initiated, differentiated and pulse-rate modulated by the threshold circuit (the trigger) (5) and evaluated in a Meßwertverarbeitung (6) and rmttols a display (7) is displayed. (Fig. 1) 2. The method according to claim 1, characterized in that two measured variables (1,1 a) with positive and / or negative sign, on two parallel capacitive converter (plate capacitors) (2,2a), are introduced. (Fig. 2) 3. A method nacl <claim 1, characterized in that the capacitive transducer (Plattenkonden capacitor) (2) by a fixed capacitor (2 b) replaced and the measured variable (1) via a Widerstandswa idler (4 a) is initiated. (Fig. 3) 4. The method according to / claim 1, characterized in that when using a capacitive transducer (2) and Λ / iderstandswandlers (4a) two measured variables (1,1a) are introduced with the same or unequal signs. (Fig. 4) 5. The method according to claim 1, characterized in that a plurality of signed measured quantities (1.1 a to 1 η) in a plurality of capacitive transducers (2.2 a to 2 n) and resistance converter (4a to 4n) are introduced.