In a liquid level sensor according to the present invention, a first detecting electrode being always in a liquid to be measured, a second detecting electrode which measures a level of the liquid to be measured, and a third detecting electrode being always out of the liquid to be measured are arranged, an operation of charging capacitor 45 for a time being in proportion to a ratio of a length of a part of the second detecting electrode in the liquid to be measured to a total length of the second detecting electrode and an operation of discharging the electric charge of the capacitor for a time being in proportion to a ratio of a length of a part of the second detecting electrode being out of the liquid to be measured to the total length of the second detecting electrode is repeated. With this configuration, the liquid level can be precisely detected without arranging a complex operational device even though a dielectric constant or a temperature of the liquid to be measured changes.

Liquid-level sensor

A carbon fiber cord for rubber reinforcement, comprising (A) a carbon fiber bundle comprising carbon fibers selected from the group consisting of carbon fibers having coated thereon from 01 to 1% by weight of at least one epoxy resin composition and carbon fibers having coated thereon from 05 to 15% by weight of a metal selected from the group consisting of copper, nickel, zinc, and cobalt, and (B) a phenol-formalin-rubber latex type adhesive for rubber impregnated to said carbon fiber bundle in an amount of from 10 to 30% by weight, and said epoxy resin is selected from the group consisting of (1) a composition comprising an epoxy resin and from 5 to 20% by weight of a compound represented by formula (I) ##STR1## wherein A represents --C2 H4 O)l or --C2 H4 O)n (C3 H6 O)m, wherein l and n each represents an integrer of from 18 to 50, m represents an integer of from 1 to 50, and n/m is from 1 to 25, (2) a composition comprising a urethane-modified epoxy resin represented by formula ##STR2## wherein A represents an aliphatic or aromatic hydrocarbon group, m and n each represents 0 or an interger of 1 or more, and the sum of n and m is from 2 to 10, and (3) a composition comprising polybutadiene epoxide resin containing a glycidyl group and having an epoxy equivalent of from 1,000 to 2,000, which is represented by formula (III) ##STR3## wherein n represents an integer of from 4 to 22, and l/m is from 23 to 9

Carbon fiber cord for rubber reinforcement and process for producing the same

PROBLEM TO BE SOLVED: To provide a physical amount detecting circuit capable of preventing a low-frequency cut-off frequency from excessively lowering SOLUTION: The physical amount detecting circuit 100 comprises an operational amplifier 110, a capacity sensor 120, a feed-back capacitor 130, a diode section 140, a switch 150 and a temperature sensor 160 The section 140 functions as a resistance, and is connected in parallel with the capacitor 130 at a feed- back route of the output terminal, and the inverting input terminal of the amplifier 110 The section 140 has diodes 142 and 144 A gate of the switch 150 is controlled by the sensor 160 When it becomes lower than a prescribed temperature, the switch 150 is closed Thus, the diodes 142 and 144 are selected, and the feed-back current flows to the diodes 142 and 144 When it becomes higher than the prescribed temperature, the switch 150 is opened Thus, since the diode 144 is selected, the feed-back current flows to the diode 144, but does not flow to the diode 142 COPYRIGHT: (C)2002,JPO

Physical amount detecting circuit

Drainage system for pumping plant

PROBLEM TO BE SOLVED: To detect a capacitance with high accuracy, while simplifying a wiring constitution, in a movable element device such as MEMS. SOLUTION: In order to detect attitude displacement to a standard attitude of the movable element 3a by the capacitance 11 between the movable element 3a and an electrode 4, an antiphase input of a noninverting amplifier 10 is connected to the electrode 4, and a driving signal and a detection signal are inputted from a positive-phase input. Hereby, the movable element 3a is driven by the noninverting amplifier 10 and the capacitance 11 is detected from the output of the noninverting amplifier 10. COPYRIGHT: (C)2005,JPO&NCIPI

Movable element device

PURPOSE:To remove the influence of stray capacitance by connecting a variable capacitor corresponding to a capacitor to be measured and a reference capacitor to the 1st rectifying circuit, controlling the oscillators of both the capacitors by the output of the 1st rectifier circuit, and obtaining an output from the 2nd rectifier circuit for the reference capacitor. CONSTITUTION:Respective fixed electrodes 16, 17 of variable and reference capacitors 11, 12 in a detecting part 10 are connected to the inverted input terminals of operational amplifiers A1, A2 of detecting circuits 51, 52 constituting the 1st and 2nd rectifier circuits respectively and the positive input terminals are connected to a common electrode 15 in the detecting circuit 10 through a reference point oscillator 20. On the other hand, the outputs of the amplifiers A1, A2 are fed back to respective inverted input terminals through feedback circuits consisting of resistors R3, R4, etc. respectively. A DC voltage from the amplifier A1 and a negative reference voltage are inputted to the inverted input terminal of an operational amplifier A3, the oscillator 20 is controlled by the output of the amplifier A3 and an output EOUT related to a capacitance value of the capacitor 11 corresponding to the capacitance to be measured is extracted from the circuit 52.

Capacitance type converter

PURPOSE:To enable correcting of a non-rectilinearity by means of a simple constitution, by constituting a device such that a pulse width signal for compensation is generated, an adder, a substractor, and a factor device are mounted, and a given computation is made using the pulse width signal for compensation and an output voltage. CONSTITUTION:A pulse width signal PW3 for compensation, having a specified pulse width ts, is obtained at a period T, corresponding to a sum of variable capacitors C1 and C2, via a flip flop FF1, an one shot circuit MM, and a comparator CP. A switch SW1 is driven by the signal W3, and after an output KV0 of a coefficient multiplier KC is set to ON or OFF, it is applied to a filter circuit PCf to output a voltage Vf. The compensation voltage Vf is applied to an adder AD2 and is added to a signal voltage V3, and this causes an output voltage Vc of the adder AD2 to accurately proportion a displacement amount x of a moving electrode 10 without being effected by a stray capacity Cs. The adjustment of a factor K of the factor device KC permits the control of a rectilinear property. This permits the correction of non-rectilinearity by means of a simple constitution.

Capacity type converter

PURPOSE:To compensate for nonlinearity effectively, by controlling the oscillating output of an oscillator so that the sum of a DC associated with the capacity of a variable capacitor, a positive DC associated with the capacity of a fixed capacitor, and a negative DC associated with the capacity of a fixed capacitor becomes constant. CONSTITUTION:The integrator of a control circuit 40 controls the oscillating output of an oscillator 20 so that the sum of a positive DC E1/R4 based on a positive DC voltage E1, a positive DC E2/R5 based on a positive DC voltage E2, a negative DC E3/R6 based on a negative DC voltage E3, and a negative DC Es/R7 based on a negative reference voltage Es becomes zero. An output voltage E0 generated at the output terminal of a current voltage converter circuit 50 becomes the value as shown by the expression ( I ), when a variable resistor R3 is adjusted so that the output voltage E0 becomes zero at the time a quantity to be measured (m) is zero, i.e., a displacement quantity (x) is zero. Therefore, when a variable resistor R2 is adjusted so as to satisfy alpha=1, the output voltage E0 becomes the value shown by E0=K(x/d)E, which exactly corresponds to the displacement quantity (x). Thus, the nonlinearily of the quantity to be measured (m) and the displacement quantity (x) of a variable electrode 11a can be compensated.

Capacity type converting device

PURPOSE: To attain both analog and digital communications at a time as well as the bidirectional digital communication by using two pairs of carrier waves of different frequencies according to the transmission directions to perform the digital communication. CONSTITUTION: The frequencies f 1 and f 2 are used for communication between a MODEM circuit 11 and a MODEM circuit 24; while the frequencies f 3 and f 4 are used for communication between the circuit 24 and the circuit 11 respectively. Thus the bidirection digital communication is possible. Then the integration of carrier waves obtained at the start through the end of the digital communication is set at zero by obtaining the coincidence of phases of carrier waves between the start and end time points of transmission or adding a DC component eliminating capacitor to the outputs of both circuits 11 and 12. Thus the DC analog signal is obtained from the both-terminal voltage of an input resistance of an analog communication device 22 via an LPF. This attains the digital communication with no interruption of analog signals. COPYRIGHT: (C)1986,JPO&Japio

Terutaka Hirata

Papers

Capacitance type converter

Capacity type converter

Capacity type converting device

2-wire type data transmitter