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
  • G01R27/26—Measuring inductance or capacitance; Measuring quality factor, e.g. by using the resonance method; Measuring loss factor; Measuring dielectric constants ; Measuring impedance or related variables
  • G01R27/2611—Measuring inductance
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/08—Measuring devices for evaluating the respiratory organs
  • A61B5/087—Measuring breath flow
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/103—Measuring devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes
  • A61B5/11—Measuring movement of the entire body or parts thereof, e.g. head or hand tremor or mobility of a limb
  • A61B5/113—Measuring movement of the entire body or parts thereof, e.g. head or hand tremor or mobility of a limb occurring during breathing
  • A61B5/1135—Measuring movement of the entire body or parts thereof, e.g. head or hand tremor or mobility of a limb occurring during breathing by monitoring thoracic expansion
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
  • G01R19/25—Arrangements for measuring currents or voltages or for indicating presence or sign thereof using digital measurement techniques
  • G01R19/252—Arrangements for measuring currents or voltages or for indicating presence or sign thereof using digital measurement techniques using analogue/digital converters of the type with conversion of voltage or current into frequency and measuring of this frequency
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
  • H03B5/00—Generation of oscillations using amplifier with regenerative feedback from output to input
  • H03B5/08—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance
  • H03B5/12—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance active element in amplifier being semiconductor device
  • H03B5/1206—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance active element in amplifier being semiconductor device using multiple transistors for amplification
  • H03B5/1212—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance active element in amplifier being semiconductor device using multiple transistors for amplification the amplifier comprising a pair of transistors, wherein an output terminal of each being connected to an input terminal of the other, e.g. a cross coupled pair
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
  • H03B5/00—Generation of oscillations using amplifier with regenerative feedback from output to input
  • H03B5/08—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance
  • H03B5/12—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance active element in amplifier being semiconductor device
  • H03B5/1231—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance active element in amplifier being semiconductor device the amplifier comprising one or more bipolar transistors
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
  • H03B5/00—Generation of oscillations using amplifier with regenerative feedback from output to input
  • H03B5/08—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance
  • H03B5/12—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance active element in amplifier being semiconductor device
  • H03B5/1237—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance active element in amplifier being semiconductor device comprising means for varying the frequency of the generator
  • H03B5/1256—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance active element in amplifier being semiconductor device comprising means for varying the frequency of the generator the means comprising a variable inductance
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
  • H03B5/00—Generation of oscillations using amplifier with regenerative feedback from output to input
  • H03B5/08—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance
  • H03B5/12—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance active element in amplifier being semiconductor device
  • H03B5/1296—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance active element in amplifier being semiconductor device the feedback circuit comprising a transformer
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
  • H03B2200/00—Indexing scheme relating to details of oscillators covered by H03B
  • H03B2200/003—Circuit elements of oscillators
  • H03B2200/0034—Circuit elements of oscillators including a buffer amplifier
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
  • H03B2200/00—Indexing scheme relating to details of oscillators covered by H03B
  • H03B2200/006—Functional aspects of oscillators
  • H03B2200/0098—Functional aspects of oscillators having a balanced output signal
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
  • H03B2201/00—Aspects of oscillators relating to varying the frequency of the oscillations
  • H03B2201/01—Varying the frequency of the oscillations by manual means
  • H03B2201/012—Varying the frequency of the oscillations by manual means the means being an element with a variable inductance

Definitions

• This invention relates to inductance or inductive reactance to frequency converter circuits particularly suited for use in monitoring biological processes.
• Electronic circuitry is widely used to monitor var ⁇ ious biological processes in critically ill patients and others. In monitoring such biological processes, minor changes therein can be critical. Accordingly, it is desirable to have electronic circuits which are highly sensitive to such small static and dynamic parameter changes and at the same time are relatively insensitive to ambient temperature variations and power supply varia- tions. These type of circuits are normally required to be portable and, as such, utilize batteries as the power source. Thus, it is also desirable for the circuit to have low current consumption.
• the present invention is an improved inductive impedance to frequency converter circuit for producing an oscillat ⁇ ing electronic output signal whose frequency is capable of variation in response to a variable inductive input impe ⁇ dance and which is sensitive to small variations in this input impedance.
• the improved inductive impedance to fre ⁇ quency converter circuit comprises a differential gain means and an LC resonant circuit element connected to the differential gain means whose resonance frequency deter- mines the frequency of the output signal.
• the improvement comprises a transformer comprising a secondary coil con ⁇ nected in parallel with the-capacitance element in the LC circuit, and a primary coil inductively coupled to the secondary coil and capable of being connected with the variable inductive input impedance, which illustratively may be an extensible conductor loop of the type previously described for use in monitoring biological processes, whereby a relatively small variation in the variable inductive input impedance is measurable as a significant variation in the resonance f equency of the resonant cir ⁇ cuit.
• the differential gain means comprises a pair of emitter coupled bipolar transistors, the collector of the first transistor being coupled through a capacitor to the base of the second transistor and the collector of the second transistor being coupled through a capacitor to the base of the first transistor.
• the output signal is taken at the collector of one of the transis- tors.
• the capacitance element of the LC cir ⁇ cuit and the secondary coil of the transformer are con ⁇ nected between the collectors of the transistors.
• the differential gain means may comprise a pair of cross coupled FETs or an operational amplifier.
• the LC resonant circuit is preferably connected between the high voltage terminals of the active elements forming the dif ⁇ ferential gain means. It should be noted that the above-described cross coupling arrangement results in an increased insensitivity to supply voltage variations.
• a small change in the variable inductive input impedance connected to the primary coil of the transformer will cause a relatively large change in the effective inductive impedance of the LC resonant cir ⁇ cuit as seen across the terminals of the capacitance ele ⁇ ment in the LC circuit and, consequently, will cause a relatively large change in the resonance frequency which is essentially determined by the product of the capac ⁇ itance and the effective inductance in the LC resonant circuit.
• the ratio betwen a change in the input inductance and the corresponding change in effective inductance in the resonant circuit is dependent upon the turn ratio and core permeability of the transformer.
• the improved inductive impedance to frequency con ⁇ verter circuit employing a transformer exhibits a much greater frequency change in response to a small change in inductive input impedance than is the case in prior art circuits in which no such transformer is employed.
• the drawing schematically illustrates an improved inductive impedance to frequency converter circuit in accordance with an illustrative emodiment of the present invention.
• An improved inductive impedance to frequency con ⁇ verter circuit for producing an oscillating electronic output signal whose frequency is variable in response to a variable input inductance is designated 10 in the FIGURE and is shown within the dotted lines.
• the circuit 10 shown in the FIGURE is intended to be illustrative only and numerical parameters stated in connection therewith are not intended to limit the scope of the invention. In the embodiment of the invention shown in the
• the inductive reactance to frequency converter 10 includes differential gain means 40 comprising identical emitter coupled n-p-n transistors 42 and 44.
• the collector of transistor 42 is coupled to the base of transistor 44 through a capacitor 46 and the collector of transistor 44 is coupled to the base of transistor 42 through another capacitor 48.
• Resistors 50, 52, 54, 56 and 58 are used to establish the operating points of transistors 42 and 44.
• transistors 42 and 44 are 2N3904 transis- tors and resistors 50, 52, 54, 56 and 58 are 15K, 33K, 33K, 4K7, and 2K7 resistors, respectively.
• the frequency of the oscillating output signal is determined by the resonance frequency of a resonant circuit 20 having an effective capacitance C and an effective inductance L.
• effective capacitance C may comprise a pair of capacitors 60 and 62 connected in parallel.
• capacitor 60 may be a 2200-5500pf NP0 capacitor and capacitor 62 may be a 390pf N750 temperature compensating capacitor having a negative linear tempera ⁇ ture coefficient.
• Effective inductance L is preferably determined by a transformer 64 comprising a diagrammatically illustrated magnetic core 66, a secondary coil 68 surrounding the core 66 and connected in parallel with the effective capac ⁇ itance C, and a primary coil 70 also surrounding the core 66.
• the primary coil 70 is preferably capable of being connected to a variable inductive input impedance, which is illustratively shown as a conventional extensible
• core 66 is a 905P A60 3B9 manufactured by Ferrox Cube Inc. and having a 10 mil air gap.
• the secondary coil 68 may illustratively comprise about _ turns of #36 wire and the primary coil 70 may illustratively comprise about 10_ turns of #31 wire.
• the circuit 10 is preferably operable on a standard 12V volt ⁇ age supply, which has been omitted for purposes of clar ⁇ ity.
• the standard 12V voltage supply is illustratively shown as being connected to the secondary coil 68 of the transformer 64 at about the 35th turn through an optional diode 72 whose purpose will be discussed below.
• the power supply is also connected to the base of transistor 44 through resistors 50 and 54 and to the base of transistor 42 through resistors 50 and 52.
• one possible application of the preferred circuit 10 is for monitoring movement of a surface by measuring inductance changes resulting from changes in the cross-sectional area of an extensible con ⁇ ductor loop, such as loop 30, disposed on the surface.
• the output signal from the preferred circuit 10 of the present invention is preferably amplified using, for example, a common emitter amplifier 10 of the present invention.
• a common emitter amplifier 80 is shown by way of example in the FIGURE and comprises p-n-p transistor 82 and biasing resistors 84 and 86.
• the voltage drop across the diode 72 preferably insures that transistor 82 is always on.
• the output signal of the preferred "5 circuit 10 is amplified since at relatively small values of input inductive reactance, which are typical for some applications here contemplated, the amplitude of the oscillating output signal is relatively small.
• transistor 82 is a 2N3906 transistor and 0 resistors 84 and 86 are 470 and 22K ohm resistors, respec ⁇ tively.
• a capacitor 88 is provided as an AC coupling capac ⁇ itor which couples the output of the common emitter ampli ⁇ fier 80 into a voltage divider 90 formed from resistors 92 5 and 94, each of which illustratively has a resistance of 220K.
• the voltage divider 90 insures that the amplified oscillating signal from the common emitter amplifier 80 oscillates around a base voltage of 6 volts, by way of example. This is often advantageous for subsequent signal 0 processing operations.
• the amplified oscillating electronic signal is processed by a commercially available divide-by-16 frequency divider 96, such as a CD4040.
• a resistance 98 which illustratively is a 4K7 resistor, is 5 preferably used to convert the output of the frequency divider 96 from a voltage signal to a current signal to * minimize interference during subsequent signal transmis ⁇ sion.
• the output signal from the frequency divider 96 may then preferably be processed by a conventional frequency to voltage converter (not shown) so that small changes in the variable input inductance are detectable as changes in a voltage output.
• the preferred circuit 10 the common emitter amplifier 80, the frequency divider 96, and the resistor 98, are all preferably packaged together and would preferably be situated near the extensible conductor loop 30 which serves as the var ⁇ iable inductive input impedance.
• the circuit 10 has a number of advantages which make it well suited for medical applications.
• the temperature sensitivity is about 20 parts per million per degree Centigrade.
• the circuit 10 has a wide dynamic frequency range and is highly sensitive to small changes in input inductance or inductive reactance.
• the output frequency is about 200 kilohertz for an open primary coil 70 and about 900 kilohertz when the primary coil 70 is shorted.
• the illus ⁇ trative circuit 10 shown in the FIGURE has been empiri- cally optimized using the above-mentioned components to achieve these results.
• circuit 10 is intended to be illustrative only, and numerous alternative embodiments of the invention may be devised by those skilled in the art without departing from the spirit and scope of the present invention as set forth in the following claims.

Landscapes

• Health & Medical Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Medical Informatics (AREA)
• Molecular Biology (AREA)
• General Physics & Mathematics (AREA)
• Physiology (AREA)
• Biophysics (AREA)
• Pathology (AREA)
• Biomedical Technology (AREA)
• Heart & Thoracic Surgery (AREA)
• Veterinary Medicine (AREA)
• Public Health (AREA)
• Surgery (AREA)
• Animal Behavior & Ethology (AREA)
• General Health & Medical Sciences (AREA)
• Oral & Maxillofacial Surgery (AREA)
• Power Engineering (AREA)
• Dentistry (AREA)
• Pulmonology (AREA)
• Networks Using Active Elements (AREA)
• Channel Selection Circuits, Automatic Tuning Circuits (AREA)
• Filters And Equalizers (AREA)

Applications Claiming Priority (1)

Publications (2)

Family

ID=22167945

Family Applications (1)

Country Status (3)

Families Citing this family (2)

Family Cites Families (11)

• 1982
  • 1982-04-16 AU AU84580/82A patent/AU8458082A/en not_active Abandoned
  • 1982-04-16 EP EP19820901691 patent/EP0106843A4/de not_active Withdrawn
  • 1982-04-16 WO PCT/US1982/000500 patent/WO1983003533A1/en not_active Ceased

Also Published As

Similar Documents

Legal Events