GB1565276A - Creación de Inventos y Patentes con Inteligencia Artificial

GB1565276A – Capacitive measuring system with zeroizing means
– Google Patents

GB1565276A – Capacitive measuring system with zeroizing means
– Google Patents
Capacitive measuring system with zeroizing means

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Publication number
GB1565276A

GB1565276A
GB7514/77A
GB751477A
GB1565276A
GB 1565276 A
GB1565276 A
GB 1565276A
GB 7514/77 A
GB7514/77 A
GB 7514/77A
GB 751477 A
GB751477 A
GB 751477A
GB 1565276 A
GB1565276 A
GB 1565276A
Authority
GB
United Kingdom
Prior art keywords
signal
filament
zero
digital
compensating
Prior art date
1976-02-23
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)

Expired

Application number
GB7514/77A
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)

MICRO SENSORS Inc

Original Assignee
MICRO SENSORS Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
1976-02-23
Filing date
1977-02-22
Publication date
1980-04-16

1977-02-22
Application filed by MICRO SENSORS Inc
filed
Critical
MICRO SENSORS Inc

1980-04-16
Publication of GB1565276A
publication
Critical
patent/GB1565276A/en

Status
Expired
legal-status
Critical
Current

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Classifications

G—PHYSICS

G01—MEASURING; TESTING

G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR

G01D18/00—Testing or calibrating apparatus or arrangements provided for in groups G01D1/00 – G01D15/00

G01D18/002—Automatic recalibration

G01D18/006—Intermittent recalibration

G—PHYSICS

G01—MEASURING; TESTING

G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES

G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means

G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance

G01N27/22—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating capacitance

G01N27/228—Circuits therefor

G—PHYSICS

G01—MEASURING; TESTING

G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES

G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 – G01N31/00

G01N33/36—Textiles

G01N33/365—Textiles filiform textiles, e.g. yarns

G—PHYSICS

G01—MEASURING; TESTING

G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES

G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere

G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections

G01R31/58—Testing of lines, cables or conductors

G01R31/59—Testing of lines, cables or conductors while the cable continuously passes the testing apparatus, e.g. during manufacture

Abstract

The thread (F) is passed through a capacitive sensor (12) which generates a sensor signal in accordance with the changes in the capacitance of the sensor (12). The zero level of the sensor signal can drift due to contamination of the sensor. To allow a reliable absolute-value measurement independent of interruptions of the measurement during the cleaning of the sensor heads, the device is equipped with a compensation arrangement (20) which is used for generating any compensation signal and for combining the signal with the sensor signal to form a composite measurement signal (20a). The compensation arrangement comprises a zero-level control arrangement which switches on when the thread (F) is removed from the sensor (12) in order to return the level of the composite measurement signal (20a) to a particular nominal value independent of the degree of contamination of the sensor.

Description

(54) CAPACITIVE MEASURING SYSTEM WITH
ZEROIZING MEANS
(71) We, MICRO-SENSORS,
INCORPORATED, of Route 126,
Holliston, Massachusetts 01745, United
States of America; a Corporation organized and exising under the laws of the State of
Massachusetts, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to systems and methods for continuously measuring and monitoring the characteristics of a moving filament, such as the denier of a synthetic yarn, by passing the filament through a capacitive sensor to develop an electrical signal representing an absolute measurement of the filament, with reference to a prescribed datum or zero point. For example, denier is a unit of fineness for yarn equivalent to 1 gram per 9,000 meters of length, referred to zero.
Thus a 15-denier weighs 15 grams per 9,000 meters. More particularly, this invention relates to a means and method for abrogating errors arising from slowly occurring variations in the capacitive sensor.
Devices and methods for capacitively monitoring the characteristics of a continuously moving filament are known. In one advantageous device, disclosed in U.S.
Patent 3,879,660 to Piso, a filament is passed through a capacitive sensor to develop an absolute measurement of the filament with reference to a prescribed datum or zero point, thus permitting the monitoring of characteristics such as the denier of synthetic yarn filaments, with the absolute measurement of denier being made available for utilization, e.g., to give an alarm if the denier measurement is outside a prescribed range of acceptable deniers.
An example of the use of such a filament monitoring device is shown schematically in
Fig. I, wherein a filament F is extruded from an extruding head E and is to be wound upon a bobbin B. The filament F passes through a slot S in a capacitive sensor head H, which is arranged to supply, on output line L, an electrical signal which varies with the capacitance of filament F, and thereby provides a measurement of the filament’s denier. It has been learned that as filaments are monitored in sensor heads H, contaminants from various sources build up between the capacitor plates in sensing head
H, causing the signal on line L to drift and no longer provide an accurate absolute measurement of the capacitance of filament
F.
Heretofore errors due to the buildup of contaminants in sensor heads H has been counteracted by periodic cleaning of the sensor heads. However, relatively commonplace filaments F promote a rapid contaminant buildup and necessitate frequent cleaning. For example, low denier filaments may contain agents which contaminate the sensor head and require it to be examined and cleaned as much as twice a week. High denier filaments, such as those used for tire cords, are subject to flaking, and sometimes have an oil finish, which lead to rapid contaminant buildup and require more frequent cleaning.
Cleaning of sensor heads necessarily requires substantial interruption of monitoring, and prevents full utilization of capacitive measurement systems in filament monitoring if accurate absolute measurements are to be maintained.
It is a principal object of the present invention to provide an improved capacitive measurement and monitoring system able to efficiently maintain accurate absolute measurements.
Accordingly the present invention consists in a device for continuously monitoring a characteristic of a moving filament comprising a capacitive sensor operative to develop an electrical filament measurement signal to represent an absolute measurement of the filament with reference to a prescribed zero datum level, and further comprising means for developing a digital zero-compensating signal representing the output of said capacitive sensor when said filament is removed from said capacitive sensor; means for storing said digital compensating signal in a digital signal storage device; and means for combining said filament measurement signal with said digital zero-compensating signal to produce a composite signal compensated for measurement signal drift arising from variations in the capacitive sensor, the storage of said digital zero compensating signal in said digital signal storage device being operative to provide a substantially drift-free zero compensating signal.
From a second aspect the present invention consists in a method of continuously monitoring the characteristics of a moving filament by passing the filament through a capacitive sensor and developing an electrical filament measurement signal to represent an absolute measurement of the filament with reference to a prescribed zero datum level comprising the steps of removing said filament from said capactitive sensor; developing while said filament is removed a digital compensating signal representing the output of said capacitive sensor; storing said digital compensating signal in a digital signal storage device: returning said filament to said capacitive sensor; and combining said filament measurement signal with said digital compensating signal to produce a composite signal compensated for measurement signal drift arising from variations in the capacitive sensor, the storage of said digital compensating signal in said digital signal storage device providing a substantially drift-free compensating signal.
In a preferred embodiment of the invention, to be described hereinbelow in detail. a moving filament is continuously monitored by passing the filament through a
capacitive sensor to develop an electrical signal to represent an absolute
measurement of the filament with reference to a prescribed datum or zero point. Means are provided for developing a compensating signal which is to be combined with the filament measurement signal to compensate
for measurement signal drift arising from
variations in the capacitive sensor. The compensating signal is developed by digitally forming and storing a signal to be
converted into the compensating signal, thereby minimizing errors arising from drift
in the compensating signal itself. The means developing the compensating signal is
arranged to produce a clock pulse train, to
digitally count the clock pulses and to
generate a digital output signal varying with
the digital count, lo detect a prescribed
comparison between the analog signal and
the input measurement signal in the absence of the filament, and to stop the clock pulses when the prescribed comparison is detected. The digital count and associated analog output signal thus become fixed at a level related to the amount of accumulated signal drift in the capacitive sensor, and provide subsequent accurate absolute measurements. In a further aspect of the invention, the means developing the compensating signal continuously receive the filament measurement signal and has means for detecting variations in the measurement signal corresponding to removal of the filament from the capacitive sensor, so that each time the filament is removed a new compensating signal will be developed automatically. The foregoing arrangement thus permits signal drifts arising from contaminants in the sensor head to be compensated very rapidly, automatically, and without requiring the sensor head to be removed from service for a significant time or to be cleaned except at considerably extended intervals, if at all.
In order that the present invention may be more readily understood, an embodiment thereof will now be described by way of example and with reference to the accompanying drawings in which: Fig. 1 is a schematic perspective view showing portions of a known capacitive filament monitoring system in operation;
Fig. 2 is a schematic view of a capacitive filament monitoring system in accordance with the present invention:
Fig. 3 is a schematic diagram of a circuit for developing a signal to compensate for measurement signal drift in accordance with the present invention
Fig. 4 is a graph of wave forms at selected points in the circuit of Fig. 3: and
Fig. 5 is a schematic diagram illustrating details of a preferred embodiment of the invention.
A capacitive measurement and monitoring system 10 arranged in accordance with the present invention to compensate for measurement signal drift arising from variations in the capacitive sensor is shown in Fig. 2. As diagramatically illustrated, system 10 utilizes a sensor head forming a capacitance bridge 12 which is driven by a signal generator 14 to provide signals first to a differential amplifier 16 and then to a demodulator 18 in the manner described in U.S. Patent 3,879,660. Briefly, in such an arrangement the filament F passes between opposed capacitors Cl and
C3 of the capacitance bridge 12. Signal generator 14 applies sinosoidal signals l and 2, which are 1800 out of phase, to bridge input terminals 12a and 12b. At bridge output terminals 12c and 12d there appear signals 1800 out of phase with amplitudes proportional to the difference between the capacitance associated with capacitors Cl and C3 and the capacitance associated with capacitors C2 and C4. The signals at terminals 12e and 12d are applied to the plus and minus inputs of the differential amplifier 16, to produce an ouput with an amplitude proportional to the difference in the capacitance associated with the two sets of capacitors Cl, C3 and
C2, C4 (i.e., a signal modulated by the capacitive characteristics of filament F).
The output from differential amplifier 16 is applied to demodulator 18 together with signal 2 from generator 14, to yield a demodulated de signal at terminal 18a which is proportional to the difference in capacitance associated with the capacitor pairs Cl, C3 and C2, C4. Since capacitors
Cl through C4 are physically identical, the signal at terminal 18a is an absolute measurement of a capacitance of filament
F. However, as contaminants build up in capcitors C1 through C4, the filament
measurement signal at the demodulator
output 18a will drift and no longer accurately represent the characteristic, such
as denier, of filament F that is to be
monitored.
In the embodiment being described the
filament measurement signal from
demodulator 18 is applied to an auto-zero
circuit 20 which, as described below,
develops a compensating signal which is
combined with the filament measurement
signal to compensate for the measurement
signal drift which arises from contaminant
accumulation in the capacitive sensor. The
compensated filament measurement signal
at the output terminal 20a of auto-zero
circuit 20, which is an accurate absolute
measurement, then may be applied through
a low pass filter 22 to a utilization circuit 24
such as the illustrated reference
comparator, which is arranged with
comparators 26, 28 and flip-flops 30, 32 to
generate outputs whenever the
compensated filament measurement signal
goes below a predetermined low limit, or
above a predetermined high limit applied
respectively to comparators 26, 28. Other
typical utilization circuits include meters,
strip charts, recorders or process control
devices.
The auto-zero circuit 20 of Fig. 2 is
illustrated in greater detail in Figs. 3 to 5.
The circuit receives an input signal at terminal 18a from demodulator 18 which is a dc measurement signal varying with
sensed capacitance and subject to drift arising from contamination of the
capacitive elements. The input filament measurements signal is combined in an adder 40 with a compensating signal Vc, developed as described below, to yield a measurement signal at output terminal 20a providing an absolute measurement of the filament which is accurately referred to a prescribed datum notwithstanding variations in the capacitive sensor.
The auto-zero circuit 20 is arranged to develop a new compensating signal Vc whenever filament F is lifted out of slot S in sensor head H, either manually or mechanically as with a solenoid. As will be evident from the following explanation, the compensating signal is developed rapidly and thus it is unnecessary for filament extruding process to be interrupted in order for compensation to take place.
The input measurement signal at terminal 18a is applied to a pulse detector 42 which detects the large scale variation in the measurement signal at terminal 18a which corresponds to removal of the filament from the capacitive sensor. The recognition of the existence of such a pulse triggers a one-shot multivibrator 44 to generate an output gate pulse which simultaneously turns on a clock pulse oscillator 46 and resets a digital counter 48. The output of the clock pulse oscillator, which is a train of clock pulses beginning at the leading edge of the gate pulse from multi-vibrator 44, drives digital counter 48 to generate, on output lines 48a, a digital output signal representing the accumulated increasing count of the clock pulses. The digital count on output lines 48a is supplied to a digitial-to-analog converter 50 which is arranged to provide an analog output at terminals 50a, 50b which varies with the digital count in counter 48. The output of the illustrated digital-to-analog converter 50 is a reesistance RDAC whose value decreases as the clock pulse train continues. The decreasing resistance RDAC is placed in series with resistor RA and RB connected respectively to positive and negative voltage of, e.g., +15 volts and -15 volts. These resistances and voltage sources form a voltage divider which develops, at terminal 50a, the compensating signal Ve which is applied as one input to adder 40. As resistance RDAC decreases, the compensating signal Vc, which is an analog signal, also decreases.
The measurement signal at input 18a, developed in sensor head H in the absence of the filament F, is combined with the decreasing compensating signal Ve in adder 40. The decreasing adder output is applied to one input of comparator 52. The other input of comparator 52 is connected to a zero reference circuit 54 which defines the datum to zero point to which the output signal at terminal 20a is to be referred.
When the output of the adder 40 matches the datum signal defined by zero reference circuit 54, the comparator 52 generates an output to stop the clock pulse oscillator 46 from generating any further clock pulses.
The counter 48 maintains its digital count, and the digital-to-analogue converter maintains its output resistance RDACS so that the appropriate zero compensating signal Vc continues to be applied to adder 40. When the filament F is reintroduced in the slot S in capacitive sensor head H, the filament measurement signal at input 18a will be offset by the fixed compensation signal Vc corresponding to the amount of accumulated signal drift arising from contaminants in the capacitive sensor. The output at terminal 20a then will be a measurement signal which is appropriately zeroed.
The operation of auto zero ciruit 20 is shown graphically in Fig. 4. As illustrated in
Fig. 4, a compensating signal Vc1 exists prior to time to, and is combined with the voltage at input terminal 18a. At time to, filament F is removed from sensor head
H. The measurement voltage applied to input terminal 18a then measures accumulated drift and has a value Adrift. As the filament is removed at time to, multivibrator 44 generates a gate pulse G whose leading edge causes clock pulse oscillator 46 to begin generating pulses, and causes counter 48 to begin counting the pulses from a reset condition. The compensating signal Vc jumps to a value +V and begins steadily to decrease. The output of the adder is VC+Vdrift, which decreases until time t, when the compensating signal reaches a value Vc2 which, when combined with Vdr,ft, matches the zero reference signal from circuit 54 and comparator 52 stops clock pulse oscillator 46. The compensating signal thereafter stays fixed at value Vc2 and, at a time t2 when the filament is returned to sensor head H, the output voltage at terminal 20a is the input measurement signal (containing drift) +Vc2, which is an appropriately zeroed measurement signal.
The auto-zero circuit 20, as described above, provides a compensating signal V0 which can be generated quickly, for example within a fraction of a second. The compensating signal V0 itself relatively free from drift effects since its value is digitally stored in counter 48, and is converted in a digital-to-analog converter, a device relatively free from drift. The pulse detector 42 permits automatic operation to be initiated simply by lifting the filament from sensor head H. Alternatively, if the filament is to be removed from slot S with a solenoid or like device, a separate starting signal can be provided, using gate pulse G to time the duration of filament absence from slot S. It should be noted further that auto-zero circuit 20 effects a comparison of the prescribed datum with the output of the adder circuit which combines the filament measurement signal with the compensating signal V, and thereby automatically compensates for any drift which may arise in adder 40.
Fig. 5 illustrates in detail the construction of an auto-zero circuit 20A of the type described above. Pulse detector 42 has an input high pass filter formed with capacitor
C2′ and diode CR2 at the input to amplifier Al-A which responds to gross changes in the input signal to trigger multivibrator 44.
as shown, a terminal ZRO at the input to multivibrator 44 is provided to manually apply a trigger signal. The multivibrator 44 is formed with an oscillator section Ul-A arranged to function in a monostable mode, and to have a gate pulse output to start clock pulse oscillator 46. Clock pulse oscillator 46 is formed with an oscillator section Ul-B connected for free running operation at, e.g., 1 K Hertz. The counter 48 is formed with two four bit counters U3 and
U4, and has eight output lines 48a connected to digital-to-analog converter 50.
The output voltage at pin 1 of converter 50, which corresponds to terminal 50a in the converter shown in Fig. 3, is fed to the input of adder 40, which is formed with an operational amplifier Al-B. Comparator 52 is formed with an amplifier section Al
C, with a zero reference circuit 54 connected to its positive input terminal. The zero reference circuit 54 comprises a potentiometer R26 connected between positive and negative voltage sources of + 15 volts and -15 volts with the intermediate potentiometer contact connected through a resistor R22 to the positive terminal of comparator 52. Accordingly, the zero reference can be adjusted or trimmed to provide accurate calibration.
In Fig. 5, the numbers adjacent the various amplifiers oscillators, counters and converter represent the pin numbers of exemplary devices as applied by the manufacturers thereof. As illustrated, the amplifier sections Al-A through Al-C are sections of a National Semiconductor model 324 component, the oscillator sections Ul- A and Ul-B are National Semiconductor model 556 components, the counter sections U3 and U4 are Texas Instruments model 74L93 components, and the digitalto-analog converter U2 is an Analog
Devices, Inc. model AD 7520KN component. The ground connections indicated as A and D are developed as shown in the lower lefthand corner of Fig. 5.
The values of the resistors and capacitors in auto-zero circuit 20A in Fig. 5 may take the values indicated below:
RI, R2 30.9K
R6 100K R7 10K
R8 56K
R9 4.7K R10 10K Ril 1M R15, R16 22K
R17 47K
R18 150
RA 180K
RB 80.6K
R22 IM
R23 4.99
R26 5M C2′ 3.3 microfarads
C6 4.7 microfarads
C7 0.1 microfarads
C8 0.22 microfarads
From the foregoing it is apparent that a capacitive measuring and monitoring system has been described with means to counteract measurement signal drift arising from contamination of the capacitive sensor using standard components and devices in a circuit that can be constructed easily and at a cost which compares quite favorably with the cost of removing contaminants by frequent cleansing of a sensor head.
While a particular preferred example of an auto-zero circuit accomplishing these goals has been described with reference to
Fig. 5, it will be understood that other circuit configuration components, and element values and models can be designed by those skilled in the art to realize the present invention.
WHAT WE CLAIM IS:
1. A device for continuously monitoring a characteristic of a moving filament comprising a capacitive sensor operative to develop an electrical filament measurement signal to represent an absolute measurement of the filament with reference to a presecribed zero datum level, and further comprising means for developing a digital zero-compensating signal representing the output of said capacitive sensor when said filament is removed from said capacitive sensor; means for storing said digital compensating signal in a digital signal storage device; and means for combining said filament measurement signal with said digital zero-compensating signal to produce a composite signal compensated for measurement signal drift arising from variations in the capacitive sensor, the storage of said digital zero compensating signal in said digital signal storage device being operative to provide a substantially drift-free zero compensating signal.
2. A device as claimed in claim 1 further comprising control means normally
inoperative while said monitoring device is functioning but operative to establish the zero level of said composite signal at a predetermined zero-datum level; said control means including: a signal-setting circuit operative to set the value of said zero-compensating signal to a predetermined level which, when said filament is temporarily removed from said sensor, results in a composite signal offset from said zero-datum level; a signal-varying circuit operative to vary said zerocompensating signal through a range of values from said predetermined level and moving in a direction which alters said composite signal towards said zero-datum level; a comparator device responsive to said composite signal and to said predetermined zero datum level, said comparator device being operative to produce an output signal indicating when said composite signal has reached said zerodatum level; and means responsive to said comparator output signal for stopping the variation of said zero-compensating signal at the particular value which resulted in a composite signal at said zero-datum level; said digital signal storage device being arranged to maintain said zerocompensating signal at said particular value after said control means has been deactivated and said device has resumed
normal operation monitoring the
characteristic of said moving filament.
3. A device as claimed in claim 2, wherein said digital signal storage device is a
counter.
4. A device as claimed in claim 3, and including a digital-to-analog converter means for converting the digital value
stored in said counter to an analog signal to
serve as said zero-compensating signal, and
means for varying said analogue signal in
response to the digital value stored in said
counter.
5. Apparatus as claimed in claim 2, wherein said sensor signal and said zero
compensating signal both are dc current
signals; said signal setting circuit including
means to drive said compensating signal in
one polarity to a value substantially
different from that which normally provides
for proper compensation; said signal
varying circuit being operable to alter said
compensating signal at a predetermined
constant rate-of-change.
6. A method of continuously monitoring
the characteristics of a moving filament by
passing the filament through a capacitive
sensor and developing an electrical filament
measurement signal to represent an
absolute measurement of the filament with
reference to a prescribed zero datum level
comprising the steps of: removing said
filament from said capacitive sensor;
developing while said filament is removed a
digital compensating signal representing the
output of said capacitive sensor; storing said
digital compensating signal in a digital signal
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (8)

**WARNING** start of CLMS field may overlap end of DESC **. R9 4.7K R10 10K Ril 1M R15, R16 22K R17 47K R18 150 RA 180K RB 80.6K R22 IM R23 4.99 R26 5M C2′ 3.3 microfarads C6 4.7 microfarads C7 0.1 microfarads C8 0.22 microfarads From the foregoing it is apparent that a capacitive measuring and monitoring system has been described with means to counteract measurement signal drift arising from contamination of the capacitive sensor using standard components and devices in a circuit that can be constructed easily and at a cost which compares quite favorably with the cost of removing contaminants by frequent cleansing of a sensor head. While a particular preferred example of an auto-zero circuit accomplishing these goals has been described with reference to Fig. 5, it will be understood that other circuit configuration components, and element values and models can be designed by those skilled in the art to realize the present invention. WHAT WE CLAIM IS:

1. A device for continuously monitoring a characteristic of a moving filament comprising a capacitive sensor operative to develop an electrical filament measurement signal to represent an absolute measurement of the filament with reference to a presecribed zero datum level, and further comprising means for developing a digital zero-compensating signal representing the output of said capacitive sensor when said filament is removed from said capacitive sensor; means for storing said digital compensating signal in a digital signal storage device; and means for combining said filament measurement signal with said digital zero-compensating signal to produce a composite signal compensated for measurement signal drift arising from variations in the capacitive sensor, the storage of said digital zero compensating signal in said digital signal storage device being operative to provide a substantially drift-free zero compensating signal.

2. A device as claimed in claim 1 further comprising control means normally
inoperative while said monitoring device is functioning but operative to establish the zero level of said composite signal at a predetermined zero-datum level; said control means including: a signal-setting circuit operative to set the value of said zero-compensating signal to a predetermined level which, when said filament is temporarily removed from said sensor, results in a composite signal offset from said zero-datum level; a signal-varying circuit operative to vary said zerocompensating signal through a range of values from said predetermined level and moving in a direction which alters said composite signal towards said zero-datum level; a comparator device responsive to said composite signal and to said predetermined zero datum level, said comparator device being operative to produce an output signal indicating when said composite signal has reached said zerodatum level; and means responsive to said comparator output signal for stopping the variation of said zero-compensating signal at the particular value which resulted in a composite signal at said zero-datum level; said digital signal storage device being arranged to maintain said zerocompensating signal at said particular value after said control means has been deactivated and said device has resumed
normal operation monitoring the
characteristic of said moving filament.

3. A device as claimed in claim 2, wherein said digital signal storage device is a
counter.

4. A device as claimed in claim 3, and including a digital-to-analog converter means for converting the digital value
stored in said counter to an analog signal to
serve as said zero-compensating signal, and
means for varying said analogue signal in
response to the digital value stored in said
counter.

5. Apparatus as claimed in claim 2, wherein said sensor signal and said zero
compensating signal both are dc current
signals; said signal setting circuit including
means to drive said compensating signal in
one polarity to a value substantially
different from that which normally provides
for proper compensation; said signal
varying circuit being operable to alter said
compensating signal at a predetermined
constant rate-of-change.

6. A method of continuously monitoring
the characteristics of a moving filament by
passing the filament through a capacitive
sensor and developing an electrical filament
measurement signal to represent an
absolute measurement of the filament with
reference to a prescribed zero datum level
comprising the steps of: removing said
filament from said capacitive sensor;
developing while said filament is removed a
digital compensating signal representing the
output of said capacitive sensor; storing said
digital compensating signal in a digital signal
storage device; returning said filament to said capacitive sensor; and combining said filament measurement signal with said digital compensating signal to produce a composite signal compensated for measurement signal drift arising from variations in the capacitive sensor, the storage of said digital compensating signal in said digital signal storage device producing a substantially drift-free compensating signal.

7. A device for continuously monitoring a characteristic of a moving filament substantially as hereinbefore described with reference to the accompanying drawings.

8. A method of continuously monitoring a characteristic of a moving filament substantially as hereinbefore described with reference to the accompanying drawings.

GB7514/77A
1976-02-23
1977-02-22
Capacitive measuring system with zeroizing means

Expired

GB1565276A
(en)

Applications Claiming Priority (1)

Application Number
Priority Date
Filing Date
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US66039876A

1976-02-23
1976-02-23

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true

GB1565276A
(en)

1980-04-16

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Expired

GB1565276A
(en)

1976-02-23
1977-02-22
Capacitive measuring system with zeroizing means

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JPS52117154A
(en)

CH
(1)

CH615997A5
(en)

DE
(1)

DE2707000A1
(en)

GB
(1)

GB1565276A
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CH671981A5
(en)

1986-11-06
1989-10-13
Zellweger Uster Ag

CH671980A5
(en)

1986-11-06
1989-10-13
Zellweger Uster Ag

DE4025899C2
(en)

1990-08-16
2000-06-08
Rieter Ag Maschf

Method and device for determining the uniformity of a test material from textile yarns

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CH355973A
(en)

1958-01-18
1961-07-31
Zellweger Uster Ag

Method and device for continuous monitoring of the titre of a test item, in particular a yarn

US3185924A
(en)

1959-07-14
1965-05-25
Zellweger Uster Ag
Apparatus utilizing capacitance measuring means for the continuous monitoring of elongate materials during production to permit determination of the devlation of the denier from a desired value

NL271951A
(en)

1961-07-25

US3879660A
(en)

1973-10-24
1975-04-22
John S Piso
Capacitive measuring system

1977

1977-02-18
DE
DE19772707000
patent/DE2707000A1/en
not_active
Ceased

1977-02-22
NL
NL7701890A
patent/NL7701890A/en
unknown

1977-02-22
CH
CH220177A
patent/CH615997A5/en
not_active
IP Right Cessation

1977-02-22
GB
GB7514/77A
patent/GB1565276A/en
not_active
Expired

1977-02-23
JP
JP1908277A
patent/JPS52117154A/en
active
Pending

Also Published As

Publication number
Publication date

CH615997A5
(en)

1980-02-29

JPS52117154A
(en)

1977-10-01

DE2707000A1
(en)

1977-08-25

NL7701890A
(en)

1977-08-25

Información de contacto