JP5089048B2 - Multiple signal readout circuit - Google Patents

Description

  The present invention relates to a multiple signal readout circuit for simultaneously reading out signals emitted from a plurality of signal sources, and more specifically, radiation measurement such as an imaging type / ultra-high wavelength resolution X-ray detector, and imaging type / high sensitivity infrared detection. The present invention relates to a multiple signal readout circuit that can be suitably used in the field of heat measurement of a thermometer.

  A calorimeter (microcalorimeter) that uses the temperature change of the steep resistance value at the superconducting transition edge of a superconductor is an important detector as an ultra-high wavelength resolution X-ray detector or a highly sensitive infrared detector. . However, when the microcalorimeter is actually used as an imaging device such as an X-ray detector attached to an astronomical satellite, for example, it is necessary to arrange a large number of microcalorimeters and independently read out signals from each microcalorimeter. . The microcalorimeter is operated at an extremely low temperature of about 0.1 K. In such an application, the current signal generated from a large number of signal sources is amplified at an extremely low temperature and can be taken out to the room temperature region. There is a need for a multiple signal readout circuit.

  As a method for detecting a current signal in an extremely low sound, there is a means for converting a current signal into a voltage signal using a superconducting quantum interference device (hereinafter referred to as SQUID) installed at an extremely low temperature. Conventionally, as means for detecting a large number of signals using a SQUID, the following is known (see, for example, Patent Document 1). A plurality of pickup coils are provided, and a number of SQUIDs corresponding to each pickup coil and a drive circuit installed at room temperature are provided in order to measure the magnetic flux linked to each pickup coil. Each pickup coil is connected to an input coil that is magnetically coupled to a superconducting loop that includes two Josephson junctions. The magnetic flux interlinked with the pickup coil is transmitted to the inductance of the superconducting loop via the input coil. Further, a modulation coil is provided for inputting a feedback current supplied from the drive circuit to the superconducting loop.

  The drive circuit mainly consists of a bias current source for SQUID, an amplifier, and an integrator. By supplying a direct current from the bias current source for SQUID to the SQUID, the SQUID functions as a current-voltage conversion element that outputs a voltage signal in response to a current signal input to the input coil.

  Next, the magnetic flux lock loop operation by the drive circuit will be described. A voltage signal output from the SQUID passes through an amplifier and an integrator and is taken out as an output voltage. The output voltage is converted into a current and applied to the modulation coil as a feedback current. When the magnetic flux lock loop is driven, the drive circuit controls the feedback current so that the magnetic flux in the superconducting loop is always constant. As a result, the output voltage of the drive circuit takes a value proportional to the current value input to the input coil. By providing an individual SQUID and an individual drive circuit for each signal source, signals emitted from each signal source can be read with high accuracy.

  As means for detecting a plurality of signals emitted from a plurality of signal sources with one SQUID, the following is known (for example, see Patent Document 2). The SQUID is configured to detect four input signals, and the SQUID inductance constituting the SQUID superconducting loop is composed of four divided coils (hereinafter referred to as divided coils). Each divided coil is magnetically coupled with an individual signal input coil corresponding to each channel. The modulation coil for inputting the feedback current supplied from the drive circuit is composed of four divided coils (hereinafter referred to as divided modulation coils), and each divided modulation coil is magnetically coupled to the divided coils. Further, by connecting all the divided modulation coils in series, it is possible to apply a feedback current to the entire superconducting loop with a single drive circuit.

By configuring the SQUID in this way, signals emitted from four signal sources can be read out by one SQUID and one driving circuit, so that a multiple signal reading circuit with a small number of wirings can be provided. In addition, by dividing the SQUID inductance constituting the superconducting loop into the same number as the input signal source, each input signal coil can be installed in an individual divided loop, so that the element structure has good symmetry.
JP-A-5-172918 Japanese Patent Laid-Open No. 2000-323761

  When the micro calorimeter is applied to an actual image sensor, a large number of wirings are required for each micro calorimeter, such as a wiring for applying a bias current for operating the micro calorimeter and a wiring for reading. Therefore, when the conventional technology is applied as it is, a large number of wirings at a very low temperature must be taken out to a measurement area at room temperature where a circuit for reading is installed, and the number of wirings increases and the circuit becomes complicated. there were. In addition, since the number of wirings increases, heat penetration increases from room temperature, and the circuit is cooled, so that a large-scale cooling means is required.

  In addition, in order to read out signals from a plurality of signal sources simultaneously and with high accuracy, it is also important to reduce signal crosstalk between channels. In the SQUID disclosed in Patent Document 2, the input signal coils are individually coupled to the divided coils, but the modulation coils are coupled to all the divided coils. For this reason, crosstalk occurs between the channels via the modulation coil. As a result, when signals are simultaneously input from a plurality of signal sources, it is difficult to identify whether the signals are due to input signals or due to crosstalk.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a multiple signal readout circuit that has a small number of wires, reduces the burden on the cooling means, and reduces crosstalk between channels.

  In order to achieve the above object, the present invention provides the following means.

It consists of a plurality of signal input coils for inputting a plurality of current signals emitted from a plurality of signal sources and a superconducting loop including two Josephson junctions, and the plurality of signal input coils and the modulation coil are magnetically coupled. A superconducting quantum interference device, and a drive circuit for supplying power to the superconducting quantum interference device and returning a feedback current to the modulation coil to obtain an output voltage linearized with respect to the current signal. The superconducting loop is divided into a plurality of divided coils having the same shape, and the divided coils are connected in parallel or in series, and the signal input coil is divided into the same number of divided input coils as the divided coils, constituted by parallel or serial connection the divided input coils, modulation coils, the same number of division modulation coil and split coil Was split, it constitutes by parallel or serial connection division modulation coil.

  According to the present invention, since a plurality of signals can be detected with one SQUID, a multiple signal readout circuit with a small number of wirings can be provided.

  Further, according to the present invention, in the superconducting loop, together with the magnetic flux due to the current signal input to each signal input coil, the same magnitude magnetic flux due to the feedback current supplied from the drive circuit is applied. The magnetic flux in the superconducting loop is always kept constant. Therefore, even when a current signal is input from a certain signal input terminal, the magnetic flux change in all the signal input coils is equivalently zero. As a result, the input current signal is not coupled as a magnetic flux to other signal input coils, and crosstalk between the channels can be reduced.

  Further, since the change in the magnetic flux in all the signal input coils is equivalently zero, the equivalent inductance of the input signal coil considering the feedback magnetic flux is zero. As a result, a circuit effective for reading high-speed signals can be provided.

  In the present invention, the number of divided input coils constituting the signal input coil and the number of divided modulation coils constituting the modulation coil may be equal to or less than the number of divided coils.

  According to the present invention, a plurality of signals can be detected by one SQUID, so that a multiple signal readout circuit with a small number of wires can be provided, crosstalk between channels can be reduced, and an equivalent of an input signal coil can be provided. Effective for inductance reduction.

  In the present invention, the signal input coil and the modulation coil are not divided, and both the plurality of signal input coils and the modulation coil are magnetically coupled to one of the divided coils.

  According to the present invention, a plurality of signals can be detected by one SQUID, so that a multiple signal readout circuit with a small number of wires can be provided, crosstalk between channels can be reduced, and inductance of an input signal coil can be reduced. It is valid.

  Further, in the present invention, an AC bias power source for driving a plurality of signal sources with AC biases having different frequencies, and an output voltage of the drive circuit is input to the signal input coil using the AC bias frequency as a reference signal. And a control circuit having a function of classifying the voltage signal corresponding to the current signal.

  According to the present invention, alternating current biases of different frequencies applied to the respective element groups are superimposed as carriers on signals from elements belonging to different element groups. Therefore, by adding these signals, an added signal multiplexed in the frequency space can be obtained. According to the present invention, the multiplexed addition signal is taken out on one signal line. That is, an added signal in which a plurality of signals are multiplexed on one signal line can be obtained. Therefore, signals from a plurality of elements can be read without requiring wiring for each element.

  According to the present invention, since signals input from a plurality of signal sources can be taken out as a multiplexed addition signal with one signal line, the number of wirings can be reduced. Further, since the crosstalk between the channels can be reduced, the signal of each element can be read with high accuracy.

  Hereinafter, the present invention will be described in detail based on embodiments of the invention.

FIG. 1 shows a configuration diagram of a multiple signal readout circuit showing Example 1 of the present invention, and FIG. 2 shows a schematic diagram of a superconducting quantum interference device (hereinafter referred to as SQUID) used in this embodiment. 1 is 2

This is a circuit for reading out current signals Iin # A and Iin # B generated by two elements. In FIG. 1, two signal input terminals TA and TB for inputting current signals Iin # A and Iin # B are provided. Signal input to the terminal TA, divided input coil 31A which is divided into two, the signal input coils constructed from 32A are connected. The two divided input coils 31A and 32A are connected in series. Similarly, even if the signal input terminal TB, 2 two to split split input coil 31B, the signal input coils constructed from 32B are connected. The two divided input coils 31B and 32B are connected in series. In this embodiment, as can be seen from FIGS. 1 and 2, the signal input terminals TA and TB for two channels are provided separately for each divided coil.

  The SQUID 10 includes two Josephson junctions 1 and two divided coils 21 and 22 divided into two. The two split coils 21 and 22 are connected in parallel so that the directions of the shielding currents flowing in the split coils are opposite to each other with respect to the interlinking magnetic flux. With this structure, when a uniform magnetic field is applied to the SQUID, the magnetic flux in the superconducting loop is canceled between both split coils and is not detected. The split coil 21 and the split coil 22 constitute two superconducting loops so as to share the two Josephson junctions 1.

  An input coil 31A corresponding to the signal input terminal TA, 31B corresponding to the signal input terminal TB, and the split modulation coil 41 are magnetically coupled to one split coil 21 with mutual inductances Min, Min, and Mf, respectively. The other split coil 22 is magnetically coupled with a split input coil 32A corresponding to the signal input terminal TA, 32B corresponding to the signal input terminal TB, and a split modulation coil 42 with mutual inductances Min, Min, and Mf, respectively. Yes. The modulation coil for inputting the feedback current supplied from the drive circuit is divided into two divided modulation coils 41 and 42 and connected in series so that the feedback current is applied to the entire superconducting loop by one drive circuit 20. be able to.

  The drive circuit 20 includes a SQUID bias current source 11, an amplifier 12, an integrator 13, and a voltage-current converter 14. By supplying a direct current from the SQUID bias current source 11 to the SQUID 10, the SQUID 10 functions as a current-voltage conversion element that outputs a voltage signal in response to a current signal input to the signal input coil. When no signal is input to the modulation coil, the total flux Φs in the superconducting loop of the SQUID is equivalent to the flux Φin # A (= Min In # A) by the current signal Iin # A and the current signal Iin # B. Is added, and the multiplexed value Φs = Φin # A + Φin # B is obtained. The SQUID 10 outputs a voltage signal Vs (= VΦ (Φin # A + Φin # B)). Here, VΦ represents the magnetic flux-voltage conversion coefficient of SQUID10.

  Next, the operation of the magnetic flux lock loop by the SQUID 10 by the drive circuit 20 will be described. The voltage signal Vs output from the SQUID 10 is amplified by the amplifier 12 and converted into the voltage signal Va. The voltage signal Va is integrated by the integrator 13 and converted to the output voltage Vout. The output voltage Vout is converted into a current by the voltage-current converter 14 and applied to the two divided modulation coils 41 and 42 as a feedback current If. A feedback magnetic flux Φf (= Mf If) is input into the superconducting loop. The drive circuit 10 at the time of driving the magnetic flux lock loop performs control so that the magnetic flux Φs (= Φin # A + Φin # B + Φf) in the superconducting loop is always constant. The output voltage Vout of the drive circuit 20 is expressed by Vout = ZfΦf / Mf using the feedback magnetic flux Φf and the conversion coefficient Zf of the voltage-current converter 14, and is a value obtained by adding the input current signals Iin # A and Iin # B. Gives a value proportional to.

  According to the present embodiment, since the current signals generated by the two signal sources can be detected by one SQUID, it is possible to provide a multiple signal readout circuit with a small number of wires.

  During the magnetic flux lock loop operation, the magnetic flux in both the split coils 21 and 22 is always constant. As a result, as can be seen from FIG. 2, the magnetic flux passing through the split input coils 31A and 32A to which the input current Iin # A is input and the split input coils 31B and 32B to which the input current Iin # B is input is always constant. . As a result, crosstalk between the channels is reduced, and two signals can be read with higher accuracy.

  Further, since the magnetic flux passing through the divided input coils 31A, 32A, 31B, 32B does not change, the equivalent inductance of the signal input coil becomes zero. As a result, the multiple signal readout circuit in this embodiment is effective for wideband measurement. In particular, in order to increase the sensitivity of the readout circuit, a means is used in which the signal input coil is composed of a large number of windings wound in a spiral shape. In that case, the self-inductance that affects the frequency band becomes very large. In this embodiment, the equivalent inductance considering the feedback current of the signal input coil during the magnetic flux lock loop operation can be reduced to zero, so that both high-accuracy measurement and wide-band measurement with high sensitivity can be achieved.

  In addition, the SQUID structure of this embodiment does not detect a uniform magnetic field. Of the magnetic coupling to the superconducting loop by the current signal input from the signal input terminal, magnetic coupling other than the magnetic coupling between the split input coil and the split coil on the split coil can be reduced, so the superconductive loop and the signal input The input current signal can be accurately measured by using the mutual inductance with the coil.

Further, the SQUID of this embodiment has a structure in which a superconducting loop is divided and connected in parallel. When m divided coils having a self-inductance L are connected in parallel, the self-inductance of the entire superconducting loop is represented by L / m ² . Since the noise of SQUID is proportional to the 0.5th power of the self-inductance, the noise can be reduced and the signal can be read with high accuracy by using a multi-loop structure connected in parallel.

  In the present embodiment, the signal input coils are divided, and each divided input coil is magnetically coupled to two divided coils, so that the signal input terminals TA and TB are separately provided for each divided coil. As a result, as shown in FIG. 2, a multi-input signal detection SQUID having good symmetry can be configured. Good symmetry can improve the measurement accuracy because the magnetic coupling to the SQUID for the input current applied to each channel can be made uniform. The SQUID shown in FIG. 5 of Patent Document 2 also has a structure with good symmetry because a signal input terminal is arranged for each divided coil. However, the input signal coil corresponding to each channel is magnetically coupled to each individual divided coil, and the modulation coil is magnetically coupled to all the divided coils. Crosstalk between channels occurs.

  The drive circuit returns feedback magnetic flux to the entire superconducting loop via the modulation coil. The feedback magnetic flux fed back to the entire superconducting loop is equal to the magnetic flux applied to one split coil by the current signal input to the signal input coil. For this reason, even during the input magnetic flux lock loop operation, the magnetic flux change in the signal input coil due to the change in the input current cannot be reduced to 0, and the equivalent inductance of the input signal coil cannot be reduced to 0.

  On the other hand, in this embodiment, in addition to the reduction in the number of wires, there is a demand for an element structure with excellent SQUID symmetry that provides uniform input sensitivity, crosstalk reduction between channels necessary for improving measurement accuracy, and broadband measurement. All the problems of reducing the inductance of the signal input coil can be solved.

  FIG. 3 shows a multiple signal readout circuit in which two divided coils are connected in series as a modification of FIG. Since the self-inductance of the superconducting loop is increased, noise is increased as compared with the multiple signal readout circuit of FIG. 1, but the number of wires is reduced, crosstalk between channels is reduced, and the equivalent inductance of the signal input coil is It has the effect of reducing.

  In this embodiment, the number of signal input coils is two, but by increasing the number, more signals can be read out.

FIG. 4 shows a configuration diagram of a multiple signal readout circuit showing Example 1 of the present invention, and FIG. 5 shows a schematic diagram of a SQUID used in this embodiment. FIG. 4 is a circuit for reading out current signals Iin # A and Iin # B generated by two elements. In FIG. 4, two signal input terminals TA and TB for inputting current signals Iin # A and Iin # B are provided. Signal input terminal TA, the TB, a signal input coils 3A, 3B are connected.

  The SQUID 10 includes two Josephson junctions 1 and two divided coils 21 and 22 divided into two. The split coils 21 and 22 are connected in parallel so that the directions of the shielding currents flowing in the split coils with respect to the interlinking magnetic fluxes are opposite to each other. With this structure, when a uniform magnetic field is applied to the SQUID, the magnetic flux in the superconducting loop is canceled between both split coils and is not detected. The two Josephson junctions 1 and the two split coils 21 and 22 constitute one superconducting loop.

  Only one split coil 22 has a signal input coil 3A corresponding to the signal input terminal TA, a signal input coil 3B corresponding to the signal input terminal TBA, and a modulation coil 4 which are magnetic with mutual inductances Min, Min and Mf, respectively. Are combined.

  The drive circuit 20 includes a SQUID bias current source 11, an amplifier 12, an integrator 13, and a voltage-current converter 14. The drive circuit 20 has the same function as that of the first embodiment. When no signal is input to the modulation coil 4, the total magnetic flux Φs in the superconducting loop of the SQUID is equivalent to the magnetic flux Φin # A (= Min In # A / 2) by the current signal Iin # A and the current signal. Magnetic flux Φin # B (= Min In # B / 2) by Iin # B is added, and a multiplexed value Φs = Φin # A + Φin # B is obtained. The SQUID 10 outputs a voltage signal Vs (= VΦ (Φin # A + Φin # B)). Here, VΦ represents the magnetic flux-voltage conversion coefficient of SQUID10. The reason that Φin # A and Φin # B are half of Min In # A and Min In # B is that the split coils are connected in parallel and the input coil is magnetically coupled to only one split coil Because.

  In this embodiment, the sensitivity to the input current signal is half that of the readout circuit shown in the first embodiment. However, as in the first embodiment, a multiple signal readout circuit with a small number of wires can be provided. In addition, it is possible to solve the problems such as the reduction of crosstalk between channels necessary for improving the measurement accuracy and the reduction of the inductance of the signal input coil required for the broadband measurement.

  FIG. 6 shows a multiple signal readout circuit in which two divided coils 21 and 22 are connected in series as a modification of FIG. Since the self-inductance of the superconducting loop is increased, the noise is larger than that of the multiple signal readout circuit of FIG. 4, but the number of wires is reduced, the crosstalk between channels is reduced, and the equivalent inductance of the signal input coil is It has the effect of reducing.

  In this embodiment, the number of signal input coils is two, but by increasing the number, more signals can be read out.

  FIG. 7 is a configuration diagram of a multi-input signal readout circuit showing Embodiment 3 of the present invention.

  In FIG. 7, two microcalorimeters 5 as passive elements are used. Further, the SQUID 10 that functions as signal addition is connected to the microcalorimeter 5, and the output current signals Iin # A and Iin # B from the microcalorimeter 5 are added to obtain one added signal. ing. The addition signal Vs of SQUID10 is processed by the drive circuit 20, and an output voltage Vout corresponding to the current signals Iin # A and Iin # B is output.

  The two calorimeters 5 are applied with AC biases having different frequencies Vac # A and Vac # B from an AC bias power source 15, respectively. Thereby, each microcalorimeter 5 is in an operating state, and when receiving external information such as X-rays, for example, an information signal from each microcalorimeter 5 based on this external information is superimposed on an AC bias as a carrier. As a result, an output signal with a predetermined frequency is emitted from each micrometer 5.

  Output signals from the respective microcalorimeters 5 are added by the SQUID 10, and as a result, an addition signal multiplexed in the frequency space can be obtained. That is, the signal from the plurality of microcalorimeters 5 arranged for each row is taken out and read out as a sum signal multiplexed in the frequency space with one signal line without requiring wiring for each microcalorimeter. Can do.

  The output voltage Vout multiplexed in the frequency section is sent to the arithmetic processing circuit 16 and is identified as an individual signal of each microcalorimeter using the carrier signal frequencies Vac # A and Vac # B.

  Therefore, the simultaneous signal readout method from a plurality of elements according to the present invention can be suitably used for an imaging element using a microcalorimeter in which it is difficult to provide a large number of wirings.

  Note that the frequency of the AC bias applied to the element group 5 is sufficiently larger than the signal band (usually 10 kHz) of the microcalorimeter, and the interval between the frequencies is sufficiently larger than the signal band.

  In the above description, a micro calorimeter is used as a passive element. However, instead of such a micro calorimeter, a bias current / voltage is applied and a voltage or current is read out. Is possible. For example, it can be used for passive elements such as thermistors and semiconductor thermometers.

1 is a configuration diagram of a multiple signal readout circuit according to Embodiment 1 of the present invention. It is a schematic diagram of the superconducting quantum interference device used in Example 1 of the present invention. FIG. 4 is a configuration diagram of a multiple signal readout circuit which is a modification of FIG. 1 and in which divided coils are connected in series. It is a block diagram of the multiple signal read-out circuit which concerns on Example 2 of this invention. It is a schematic diagram of the superconducting quantum interference device used in Example 2 of the present invention. FIG. 5 is a configuration diagram of a multiple signal readout circuit, which is a modification of FIG. 4 and in which divided coils are connected in series. It is a block diagram of the multiple signal read-out circuit which concerns on Example 3 of this invention.

Explanation of symbols

1 Josephson junction 21, 22 Split coil (split SQUID inductance)
3A, 3B Signal input coil 4 Modulation coil 5 Microcalorimeter 10 Superconducting quantum interference device (SQUID)
11 SQUID Bias Current Source 12 Amplifier 13 Integrator 14 Voltage-Current Converter 15 AC Bias Current Source 16 Arithmetic Processing Circuit 20 Drive Circuits 31A, 31B, 32A, 32B Split Input Coils 41, 42 Split Modulation Coil
TA, TB Signal input terminal TM Modulation coil input terminal TS SQUID Bias current and voltage monitor terminal

Claims (7)

A plurality of signal input coils for inputting a plurality of current signals emitted from a plurality of signal sources;
A superconducting loop containing two Josephson junctions;
An inductance of the superconducting loop; and a superconducting quantum interference device in which the plurality of signal input coils and the modulation coil are magnetically coupled;
A driving circuit for supplying power to the superconducting quantum interference device and obtaining a linearized output voltage with respect to the current signal by feeding back a feedback current to the modulation coil;
Have
The inductance of the superconducting loop is divided into a plurality of split coils having the same shape, and is configured by connecting the split coils in parallel or in series.
The signal input coil is divided into the same number of divided input coils as the divided coils, and is configured by connecting the divided input coils in parallel or in series,
A multi-input signal readout circuit configured by dividing the modulation coil into the same number of divided modulation coils as the divided coils and connecting the divided modulation coils in parallel or in series.   2. The multi-input signal readout circuit according to claim 1, wherein the divided coils are connected in parallel or in series so that the directions of the shield currents flowing in the divided coils are opposite to each other with respect to the interlinkage magnetic flux. A plurality of signal input coils for inputting a plurality of current signals emitted from a plurality of signal sources;
A superconducting loop including two Josephson junctions,
An inductance of the superconducting loop; and a superconducting quantum interference device in which the plurality of signal input coils and the modulation coil are magnetically coupled;
A driving circuit for supplying power to the superconducting quantum interference device and obtaining a linearized output voltage with respect to the current signal by feeding back a feedback current to the modulation coil;
Have
Inductance of the superconducting loop, is divided into a plurality of divided coils having the same shape, is constituted by parallel or serial connection of the divided coil,
The signal input coil is divided into divided input coils equal to or less than the number of the divided coils, and is configured by connecting the divided input coils in parallel or in series.
A multi-input signal read circuit configured by dividing the modulation coil into divided modulation coils equal to or less than the number of the divided coils, and connecting the divided modulation coils in parallel or in series.   The multi-input signal readout circuit according to claim 3, wherein the divided coils are connected in parallel or in series so that the directions of the shield currents flowing in the divided coils are opposite to each other with respect to the interlinkage magnetic flux. A plurality of signal input coils for inputting a plurality of current signals emitted from a plurality of signal sources;
A superconducting loop containing two Josephson junctions;
A superconducting quantum interference device in which the inductance of the superconducting loop, the plurality of signal input coils and the modulation coil are magnetically coupled;
A driving circuit for supplying power to the superconducting quantum interference device and obtaining a linearized output voltage with respect to the current signal by feeding back a feedback current to the modulation coil;
Have
The inductance of the superconducting loop is divided into a plurality of split coils having the same shape,
It is configured by connecting the divided coils in parallel or in series,
A multi-input signal readout circuit in which both of the plurality of signal input coils and the modulation coil are magnetically coupled to one of the divided coils.   6. The multi-input signal readout circuit according to claim 5, wherein the divided coils are connected in parallel or in series so that the directions of the shielding currents flowing in the divided coils are opposite to each other with respect to the interlinkage magnetic flux.   An AC bias power source for driving a plurality of signal sources with AC biases having different frequencies, and a current signal input to the signal input coil using the output voltage of the drive circuit as a reference signal with the frequency of the AC bias as a reference signal The multi-input signal readout circuit according to claim 1, further comprising an arithmetic processing circuit having a function of classifying the signal into voltage signals corresponding to.

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