Tdk Corporation

Tdk Electronics Company, Limited

Other

Olympus Optical Company, Ltd.

Jeco Kabushiki Kaisha

Shiro Nakagawa

Akihiko Kuroiwa

Atsuko Tsuchida

Kenryo Namba

Katsumi Yabusaki

Katsuaki Tanaka

Toshiki Aoi

Yoshihisa Okita

Kazuyuki Itoh

Taisuke Domon

Takehiro Imai

Eiji Takahashi

Tsutomu Kotani

Kiyoshi Matsui

Kenryo Nanba

Kenji Aizawa

Koichi Iwaki

Atsushi Wakabayashi

Yukihiro Nagahori

Eiji Takahishi

It is an object of the invention to provide a current sensor apparatus that reduces measurement errors resulting from variations in a position of a current path passing through the space inside a magnetic yoke. The current sensor apparatus comprises a ring-shaped magnetic yoke ( ) surrounding a current path ( ), part of the yoke having a gap ( ), and a magnetic sensor element ( ) placed in the gap ( ) of the magnetic yoke ( ). The magnetic sensor element ( ) detects a magnetic field in the gap ( ) generated by a current flowing through the current path ( ) to measure the current flowing through the current path ( ). The current sensor apparatus further comprises a magnetic field interrupter ( ), placed between the current path ( ) and the gap ( ), for interrupting a magnetic field corresponding to a magnetic flux generated by the current passing through the current path ( ) and not passing through the magnetic yoke ( ), so that the magnetic field would not reach the magnetic sensor element ( ).

Current sensor apparatus

A magnetic sensor apparatus comprises a magnetic detector (,) that outputs a signal responsive to a magnetic field and a magnetic substance (,) having a cavity (,) in which the magnetic detector (,) is placed. The magnetic detector (,) is placed in the cavity (,) of the magnetic substance (,). The ratio between a magnetic field (H) to be measured and a magnetic field applied to the magnetic detector (,) is set to a specific value, based on at least one of a first demagnetizing factor depending on the shape of the magnetic substance (,) and a second demagnetizing factor depending on the shape of the cavity (,). The magnetic sensor apparatus further comprises a feedback coil (,) that applies a negative feedback magnetic field to the magnetic detector (,) and a reference magnetic field coil (,) that applies a reference alternating magnetic filed to the magnetic detector (,) for controlling the property of the magnetic detector (,).

Magnetic sensor apparatus, current sensor apparatus and magnetic sensor element

It is an object of the invention to provide a magnetic sensor and a current sensor that exhibit high performance at low costs. A magnetic sensor has a magnetic core (,) having a magnetic saturation property and a sensor coil (,) wound around the magnetic core (,). An end of a detection coil (,) is connected to an end of the sensor coil (,). The other end of the detection coil (,) is grounded. The magnetic sensor further comprises a drive circuit (,) and a detection circuit (,). The drive circuit (,) has a series resonance circuit part of which is made up of the sensor coil (,). To the sensor coil (,) the drive circuit (,) supplies a resonance current flowing into the series resonance circuit as an alternating current that allows the magnetic core (,) to reach a saturation region. The detection circuit (,) detects a magnetic field to be measured by detecting variations in resonance current flowing through the sensor coil (,).

Magnetic sensor apparatus and current sensor apparatus

It is an object of the invention to provide a magnetic sensor apparatus and a current sensor apparatus each of which incorporates a fluxgate element for reducing an offset voltage and reducing variations in offset voltage. A drive section for exciting a sensor coil (,) includes a self-excited oscillation circuit having a resonant circuit part of which is made up of the sensor coil (,). The self-excited oscillation circuit includes an npn transistor (,) and a pnp transistor (,) that are amplifier elements used for continuing oscillation. The npn transistor (,) operates when an oscillation wave is on the positive side. The pnp transistor (,) operates when an oscillation wave is on the negative side. In the self-excited oscillation circuit, clamping of oscillation waves similarly occurs on both positive and negative sides. Therefore, the oscillation waveform has symmetrical positive and negative portions or has minor asymmetry if any.

Magnetic sensor measuring apparatus and current sensor non-contact measuring apparatus

An optical recording medium has deposited on a substrate a recording layer incorporating therein a cyanine dye, preferably an indoline dye, and optionally incorporating therein an autoxidizable compound or a thermoplastic resin and/or a singlet oxygen quencher.

Optical recording medium

An optical recording medium has deposited on a substrate a recording layer incorporating therein a cyanine dye, preferably an indoline dye, and optionally incorporating therein an autoxidizable compound or a thermoplastic resin andr a singlet oxygen quencher.

An oscillator circuit includes a gate G.sub.11 of C-MOS type (Q.sub.1, Q.sub.2, and the like) having the function of increasing an operating current i with increasing operating frequency. A humidity sensor HS changing electric impedance thereof in accordance with humidity is arranged in part of the oscillator circuit. The oscillator circuit converts a change in humidity into a change in frequency, causes the gate G.sub.11 to convert the change in frequency into a change in operating current i, and outputs the converted change in operating current i. Further, in order to increase the change in operating current i due to the change in frequency, a series circuit consisting of a capacitor C.sub.13 and a resistor R.sub.17 is connected to the gate G.sub.11 as a capacitive load.

Humidity meter

An absolute humidity meter in which a humidity sensor changes an electrical impedance thereof-exponentially with respect to the relative humidity. A z-f converting circuit (impedance to frequency ) generates a pulse signal corresponding to the impedance. A time constant control differentiating circuit has an impedance of a voltage control variable impedance element changed exponentially by a control voltage, and outputs a differentiated signal obtained by differentiating the pulse signal. A waveform shaping circuit outputs a pulse signal train obtained by binary-valued the differentiated signal. An integrating circuit causes a first integrating circuit to obtain the control voltage by integrating the pulse signal train and a second integrating circuit to obtain an output voltage of a relative humidity signal by integrating the pulse signal train, and obtains an absolute humidity signal by causing at least one of these integrating circuit to control the control voltage or the output voltage with increasing temperature.

Absolute humidity meter

A humidity sensor 1 has an impedance Zs thereof changed exponentially with respect to a relative humidity. A z-f conversion circuit 2 generates a pulse signal S1 corresponding to the impedance Zs. A time constant controlled differentiating circuit 3 has an impedance Zt of a voltage control variable impedance element 32 changed exponentially by a control voltage Vc, and outputs a differentiated signal S2 obtained by differentiating the pulse signal S1. A waveform shaping circuit 4 outputs a pulse signal train S3 obtained by binary-coding the differentiated signal S2. An integrating circuit 5 causes a first integrating circuit 51 to obtain the control voltage Vc by integrating the pulse signal train S3 and causes a second integrating circuit 52 to obtain a humidity signal S4 by integrating the pulse signal train S3. A bias circuit 6 applies a bias voltage to a control terminal 323 of the voltage control variable impedance element 32.

A humidity meter has a housing (1) which has a separated sensor room (5) recessed in said housing (1) for securing a humidity sensor assembly (3). The humidity meter also has an electronic circuit (2) mounted on a printed circuit board (21) fixed in said housing (1), for processing humidity signal supplied by said humidity sensor assembly (3). Some examples of the process are analog-digital conversion of measured humidity signal, visible indication on a display screen, and/or interface with external circuit. Said humidity sensor assembly (3) is removably fixed on said printed circuit board (21) which doubles as a bottom wall (53) of said sensor room (5).

A humidity meter includes a humidity-frequency converter (2) which is essentially a pulse oscillator, the oscillation frequency of which depends upon the impedance of a humidity sensor (1), a differentiation circuit (3) and a wave-form shaping circuit (4) which essentially operate as a pulse width modulator for adjusting pulse width of an output pulse of the converter (2) for assuring a linear relationship between humidity and the output signal, and an integrator (6) for integrating the output of the pulse width modulator to provide an output signal as a DC level. A feedback path (5) is provided to apply the output signal to the pulse width modulator for assuring a linear output irrespective of the exponential characteristics of the humidity sensor. Said differentiation circuit (3) has a capacitor (31), a first variable impedance element (32) which is controlled by said feedback path , and a second variable impedance element (33) coupled in series with the first variable impedance element (32).

A toner concentration detecting device for detecting a toner concentration of a two component developer including a differential transformer which is connected with a phase detecting circuit. A variable capacitance diode is connected between the primary coil and the secondary coil and a variable resistor is provided to supply the variable capacitance diode with a DC voltage to vary the capacitance of the diode. The variable resistor and DC voltage are located at a remote location from the transformer.

Toner concentration detector for a two-component developer

An A/D converter system has an A/D converter element (10) which provides a first predetermined number of digital output bits for each input analog signal. An addition device (12,70) adds linear slope potential to the input analog signal. A calculator (14) provides an average of a plurality of digital output signals of the A/D converter element so that the average has larger number of bits than the first predetermined number. The addition device is implemented by a time constant circuit (70) which functions as an integral circuit for an input analog signal, and functions as a differential circuit for a slope potential.

Growing community of inventors

Tokyo, Japan

Shiro Nakagawa