DE2346307C2 - Electrical circuit arrangement for the linear conversion of changes in capacitance depending on the measured variable - Google Patents
Electrical circuit arrangement for the linear conversion of changes in capacitance depending on the measured variableInfo
- Publication number
- DE2346307C2 DE2346307C2 DE19732346307 DE2346307A DE2346307C2 DE 2346307 C2 DE2346307 C2 DE 2346307C2 DE 19732346307 DE19732346307 DE 19732346307 DE 2346307 A DE2346307 A DE 2346307A DE 2346307 C2 DE2346307 C2 DE 2346307C2
- Authority
- DE
- Germany
- Prior art keywords
- capacities
- circuit arrangement
- voltage
- changes
- frequency
- Prior art date
- 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
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
- G01L9/12—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of variations in capacitance, i.e. electric circuits therefor
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Measuring Fluid Pressure (AREA)
- Amplifiers (AREA)
- Measurement Of Resistance Or Impedance (AREA)
Description
mechanischer Größen« von Christof Rohrbach, Die sjch an den Kapazitäten C1 und C, aufbauendenmechanical quantities «by Christof Rohrbach, Die s j c h on the capacities C 1 and C, building up
VDE Verlag, Düsseldorf 1967, insbesondere aus Ka- Spannungen
pitel G 10 sind Meßzellen bekannt, bei denen z. B. 55
der Plattenabstand von Plattenkondensatoren durch
eine Meßgröße (Kraft, Druck usw,) verändert wird.
Diese Meßzellen weisen jedoch extrem hohe Innen= 2_ . Γ/ d/ = + (1 — X) -^- ■ [ VDE Verlag, Düsseldorf 1967, in particular from Ka- tensions
pitel G 10 measuring cells are known in which z. B. 55
the plate spacing of plate capacitors
a measured variable (force, pressure, etc.) is changed.
However, these measuring cells have extremely high internal = 2_. Γ / d / = + (1 - X) - ^ - ■ [
Weiterhin sind darin elektronische Schaltungen zur βα * C, 7 * C0 J Furthermore there are electronic circuits for βα * C, 7 * C 0 J
analogen Messung kapazitiver Verstimmungen angegeben. Diese haben jedoch den Nachteil, sehr empfind- sowie «s selbst werfen mittels eines Summierverlich gegen Störungen und Veränderungen der Zu- stärkers SV summiert. Ausgehend vom entladenen leitungskapazitäten zu sein. Zustand der Kapazitäten C1 und Cj( nimmt dieanalog measurement of capacitive detuning specified. However, these have the disadvantage that they are very sensitive as well as throw themselves by means of a summing comparison against disturbances and changes in the amplifier SV . To be based on discharged line capacities. State of capacities C 1 and C j ( takes the
Weiterhin sind daraus Schaltungen zur Umformung 65 SummenspannungFurthermore, these are circuits for conversion 65 total voltage
der kapazitiven Verstimmung in Frequenzen bekannt. , ..the capacitive detuning in frequencies known. , ..
Aus dem Prospektblau über den tType 4-460 Digital U}. — UCi + Uc% + Us — _ 2 X —- · I usdt -\- us Pressure Transducer« der Firma Bell & Howell ist C J From the brochure blue about the tType 4-460 Digital U} . - UCi + Uc% + Us - _ 2 X - - I u s dt - \ - us Pressure Transducer "from Bell & Howell is C J
1 C- .. n + jn^- fu dt 1 C- .. n + jn ^ - fu dt
C|C | C1 ' JC 1 'J C0" JC 0 "J
weisen jedoch extrem hohe Innenwiderstände auf. = 2_ . Γ/ d/ = + (1 — X) -^- ■ [usdt however, have extremely high internal resistances. = 2_. Γ / d / = + (1 - X) - ^ - ■ [usdt
* J * J
(vorausgesetzt χ >Q) so lange ab, bis Null erreicht ist. sprechend besteht die Stromquelle for den Konden-Bm nachfolgender Komparator K schaltet in diesem satorC» aus einem Differenzverstärker OK» mit EinMoment mittels eines SchaltersS die Spannung«» gang> und RttckkopplungswiderstSnden R·*, Hnt, von der positiven Referenzspannung+ U0 auf die R&, Ryt und einem StrommeöwiderstandΗ% sowie negative Referenzspannung — U0 von vorzugsweise 5 einem Pufferverstärker PV%. Die Ausgangsspannungen etwa gleichem Betrag. Die auf diese Weise umgepolten von PV1 und PV%, nämlich Mc1 und «c», sowie Hs selbst Ströme »\ und it entladen nun Cx und C, und laden werden über Summierwiderstände As1, ÄS|t und As4 sie in der entgegengesetzten Richtung auf, bis wiede- in einem mit einem Rückkopplungswiderstant* Rs: rum »ε = Q erreicht ist und irs auf + U0 zurückge- geschalteten Summierverstärker SV summiert. Dessen schaltet wird. Diese Spannungsverläufe sind in F ig. Ib *o Ausgangsspannung — Mr wird einem Komparator K skizziert. Ein vollständiger Zyklus der entstehenden zugeführt, der über einen Schalter S die Umschaltung Schwingung ist nach einer Zeit von Ms besorgt.(assuming χ > Q) until zero is reached. In other words, the current source for the capacitor Bm, the following comparator K switches in this satorC "from a differential amplifier OK" with a moment by means of a switch S the voltage ""output> and feedback resistors R *, H n t, from the positive reference voltage + U 0 on the R &, Ryt and a current resistance Η% as well as negative reference voltage - U 0 of preferably 5 a buffer amplifier PV % . The output voltages roughly the same amount. The polarity reversed in this way from PV 1 and PV % , namely Mc 1 and "c", as well as Hs itself currents "\ and i t , now discharge C x and C, and are charged via summing resistors As 1 , Ä S | t and As 4 them in the opposite direction, until again in a summing amplifier SV switched back to + U 0 with a feedback resistor * Rs: rum »ε = Q is reached and irs sums. Whose is switched. These voltage curves are shown in Fig. Ib * o output voltage - Mr is sketched in a comparator K. A complete cycle of the resulting supplied, which via a switch S the switching oscillation is concerned after a time of Ms.
Eine Besonderheit stellt noch der Integrator IV dar.The Integrator IV is another special feature.
C0 Dieser konventionell mit einem Kondensator Ct undC 0 This conventionally with a capacitor Ct and
"Tx k l5 e'nem Widerstand Rt beschaltete Integrator erzeugt "Tx k l5 e 'nem resistance Rt wired integrator generates
eine Integrationsspannung, die mit KC1 gleichsinnigan integration voltage that corresponds to KC 1
κ „t,u„.n „j,!.,,· c u · t ist. Sie wird über As8 ebenfalls zu Mr addiert. Auf dieseκ "t, u". n "y,!. ,, · cu · t is. It is also added to Mr via As 8. To this
abgeschlossen, so daß die Schwmgfrequenz wdse ^ erreicbti 3 daß schou bei χ = 0 eine Schwin-closed, so that the oscillation frequency wdse ^ reachi 3 that schou at χ = 0 a oscillation
, , gung mit endlicher Frequenz erzeugt wird (»life zero·-,, generation is generated with a finite frequency (»life zero · -
/ = — = X . - _- so Effela), so daß X auch nega'.iv werden kann./ = - = X. - _- so Effela), so that X can also become negative.
T 2 C0 Die vorgeschlagene Sehr/ ^ungsanordnung bringt T 2 C 0 The proposed arrangement brings
folgende Vorteile mit sich. Zuclchst einmal ist derthe following advantages. First of all it is
proportional zur Meßgröße ist. Zusammenhang zwischen Meßgröße und Frequenzis proportional to the measurand. Relationship between measured variable and frequency
F i g. 2 zeigt ein Ausführungsbeispiel. Der Strom Z1 linear. Parasitäre Parallelkapazitäten erzeugen Fehler wird durch einen Differenzverstärker D V1 erzeugt. 25 vor. erst höherer Ordnung. Offsetspannungen sämtlicher Dieser ist mit Widerständen Ria, Rlb, R10 und Rld so Verstärker und auch des Komparators heben sich in beschaltet, daß der Spannungsabfall des Ausgangs- den entgegengesetzten Halbzyklen der synametrischen stromes an einem Widerstand A1 der Eingangsspan- Schwingung selbst auf. Schließlich haben auch Vernung proportional ist. Ein Pufferverstärker PV1 er- änderungen der Referenzspannungen + U0 und — U0 möglicht die Abhahme der Kondensatorspannung, 30 und damit auch Änderungen de«: Betriebsspannung ohne daß der Kondensator C1 belastet wird. Ent- des Umsetzers keinen Einfluß auf die Schwingfrequenz.F i g. 2 shows an embodiment. The current Z 1 is linear. Parasitic parallel capacitances generate errors is generated by a differential amplifier DV 1 . 25 before. only higher order. Offset voltages of all this is wired with resistors R ia , R lb , R 10 and R ld so the amplifier and the comparator rise in that the voltage drop of the output corresponds to the opposite half-cycles of the dynamic current at a resistor A 1 of the input span oscillation itself on. After all, have also Vernung is proportional. A buffer amplifier PV 1 changes the reference voltages + U 0 and - U 0 enables the capacitor voltage to be decreased, and thus also changes to the operating voltage without loading the capacitor C 1 . Either of the converter has no influence on the oscillation frequency.
Hierzu 1 Blatt Zeichnungen1 sheet of drawings
Claims (7)
wechsel ein bei bestimmten Summen der Lade- 15 Diese Aufgabe wirf erfindungsgemäß dadurch gespannungen der Kapazitäten umschaltender Korn- löst, daß der Generator als Dreieckoszillator ausgeparator (K) vorhanden ist. bildet ist, dessen Integrationsglieder ai>s den zweithe two capacities (C 1 ,. G 2 ), g e * Λ The object of the present invention is therefore to create one! ¥ fe * ausjeTeiner current source <against- ^ circuit arrangement of the type mentioned at the beginning too sensible to create with a constant current (/ \, I 2 ) alternating, which brings about a linear transformation and throws in with polarity, and for polarity only one oscillator circuit gets by,
15 According to the invention, this task raises the voltage of the capacitances switching grain by the fact that the generator is available as a triangular oscillator separator (K) . forms whose integrators ai> s the two
sprüche 1 bis 3, dadurch gekennzeichnet, daß die F i g. 1 ein PnnzipschaltbiJd mit zugehörigen Span-Stromquellen steuerbar sind. nungsdiagrammen und4. Circuit arrangement described in more detail according to one of the examples of the invention. In it shows
Claims 1 to 3, characterized in that the F i g. 1 a PnnzipschaltbiJd with associated span current sources can be controlled. voltage diagrams and
sprüche 1 bis 4, dadurch gekennzeichnet, daß C1 und C2 seien die Kapazitäten eines Meßaufzwischen den Kapazitäten (C1, C2) und dem 30 nehmers, der als Zweifach-Plattenkondensator ausge-Summierverstärker \SV) t ufferverstärker (PV1, bildet ist. Eine Meßgröße X verändere den Platten- PV2) geschaltet sind. abstand der beiden Kondensatoren entgegengesetzt5. Circuit arrangement according to one of the preceding figs. 2 a detailed circuit example,
Claims 1 to 4, characterized in that C 1 and C 2 are the capacities of a measurement intermediate between the capacities (C 1 , C 2 ) and the receiver, the summing amplifier \ SV) t buffer amplifier (PV 1 , A measured variable X change the plate PV 2 ) are connected. the distance between the two capacitors is opposite
sprüche 1 bis 5, dadurch gekennzeichnet, daß als6. Circuit arrangement me one of the on and linear so that
Proverbs 1 to 5, characterized in that as
in dem Integrator (IV) erzeugte Spannung (Inte- q q
grationsspannung) zur Summenspannung der Ka- 407. Circuit arrangement according to one of claims 1 to 6, characterized in that a 1 _ i (\ - Y \
voltage generated in the integrator (IV) (Inte- qq
voltage) to the total voltage of the cable 40
änderungen, enthaltend zwei gegensinnig gesteuerte 5o ' I £ _ COnst.
Kapazitäten und einen Frequenzgenerator. ,· _ _j_ β . Us JThe invention relates to an electrical system to be controlled by the same control voltage «5: circuit arrangement for | linear conversion of measured variable dependent capacitance changes in frequency- / = - k · us]
changes, containing two oppositely controlled 5o 'I £ _ CO nst.
Capacities and a frequency generator. , · _ _J_ β. Us J
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE19732346307 DE2346307C2 (en) | 1973-09-14 | 1973-09-14 | Electrical circuit arrangement for the linear conversion of changes in capacitance depending on the measured variable |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE19732346307 DE2346307C2 (en) | 1973-09-14 | 1973-09-14 | Electrical circuit arrangement for the linear conversion of changes in capacitance depending on the measured variable |
Publications (2)
Publication Number | Publication Date |
---|---|
DE2346307B1 DE2346307B1 (en) | 1974-05-16 |
DE2346307C2 true DE2346307C2 (en) | 1974-12-12 |
Family
ID=5892555
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
DE19732346307 Expired DE2346307C2 (en) | 1973-09-14 | 1973-09-14 | Electrical circuit arrangement for the linear conversion of changes in capacitance depending on the measured variable |
Country Status (1)
Country | Link |
---|---|
DE (1) | DE2346307C2 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE3528416A1 (en) * | 1985-08-08 | 1987-03-05 | Philips Patentverwaltung | Evaluating circuit for a capacitive sensor |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4165483A (en) * | 1978-01-31 | 1979-08-21 | Sundstrand Data Control, Inc. | Capacitive pick-off circuit |
-
1973
- 1973-09-14 DE DE19732346307 patent/DE2346307C2/en not_active Expired
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE3528416A1 (en) * | 1985-08-08 | 1987-03-05 | Philips Patentverwaltung | Evaluating circuit for a capacitive sensor |
Also Published As
Publication number | Publication date |
---|---|
DE2346307B1 (en) | 1974-05-16 |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
E77 | Valid patent as to the heymanns-index 1977 | ||
EHJ | Ceased/non-payment of the annual fee |