JPH08248143A - Automatic equilibrium adjusting circuit of metal detection apparatus - Google Patents
Automatic equilibrium adjusting circuit of metal detection apparatusInfo
- Publication number
- JPH08248143A JPH08248143A JP7251895A JP7251895A JPH08248143A JP H08248143 A JPH08248143 A JP H08248143A JP 7251895 A JP7251895 A JP 7251895A JP 7251895 A JP7251895 A JP 7251895A JP H08248143 A JPH08248143 A JP H08248143A
- Authority
- JP
- Japan
- Prior art keywords
- circuit
- microcomputer
- amplitude
- signal
- conversion circuit
- 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.)
- Pending
Links
- 238000001514 detection method Methods 0.000 title claims description 33
- 239000002184 metal Substances 0.000 title claims description 28
- 238000006243 chemical reaction Methods 0.000 claims abstract description 28
- 230000001360 synchronised effect Effects 0.000 claims description 16
- 230000004907 flux Effects 0.000 claims description 3
- 239000000284 extract Substances 0.000 claims 2
- 238000011109 contamination Methods 0.000 claims 1
- 238000007689 inspection Methods 0.000 abstract description 4
- 238000001914 filtration Methods 0.000 abstract description 2
- 230000010355 oscillation Effects 0.000 description 14
- 230000003321 amplification Effects 0.000 description 9
- 238000003199 nucleic acid amplification method Methods 0.000 description 9
- 230000010363 phase shift Effects 0.000 description 7
- 230000007774 longterm Effects 0.000 description 5
- 238000010586 diagram Methods 0.000 description 4
- 230000010354 integration Effects 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 230000033228 biological regulation Effects 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000003672 processing method Methods 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
Landscapes
- Measuring Magnetic Variables (AREA)
- Investigating Or Analyzing Materials By The Use Of Magnetic Means (AREA)
- Geophysics And Detection Of Objects (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】この発明は金属検出装置におい
て、特に、受信コイルから出力される受信信号を自動的
に平衡状態にさせ、その平衡状態が被検査体を磁界中に
通過させた時くずれるか否かにより、当該被検査体中の
混入金属の有無を検査する形式の金属検出装置に関する
ものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal detecting device, and more particularly, to automatically bring a received signal output from a receiving coil into a balanced state, and the balanced state collapses when an object to be inspected is passed through a magnetic field. The present invention relates to a metal detection device of a type that inspects the presence or absence of mixed metal in the inspected object depending on whether or not it is.
【０００２】[0002]
【従来の技術】まず、従来から使用されている金属検出
装置の概要について図３により説明する。この図におい
て、１は発振回路、２は前記発振回路に接続されている
発振コイル、３ａ，３ｂはこの発振コイルに対向もしく
は同軸上に配置されている受信コイルで、受信コイル３
ａ，３ｂは発振コイル２の交番磁界中に置かれ、発振コ
イルに対する２つの受信コイルの配置を幾何学的に調整
することによりその磁束が等しく鎖交するようにしてい
る。さらに２つの受信コイルに誘起された起電力を可変
抵抗４により差動バランスを調整することにより得られ
た差動電圧が信号処理回路に入力される受信信号とな
る。５は差動もしくは加算増幅回路、６は発振周波数と
同一の中心周波数をもつ帯域通過フィルタ、７は増幅回
路、１００は受信信号中に定常的に生じている信号と同
一の振幅、位相をもつキャンセル信号を発生する自動平
衡調整回路、８ａ，８ｂは第１、第２同期信号により同
期検波を行う同期検波回路、９ａ，９ｂは金属検出信号
と同一の中心周波数をもつアナログフィルタ、１０ａ，
１０ｂは同期検波回路により復調された金属検出信号の
大きさを判定する電圧比較回路、１１ａ，１１ｂは前記
同期検波回路８ａ，８ｂに供給する第１、第２同期信号
の位相を変更する第１、第２移相回路である。このよう
な構成からなる金属検出装置では、発振コイル２と受信
コイル３ａ，３ｂ間もしくは発振コイル及び受信コイル
中に被検査体を通過させた時、該被検査体に金属が混入
している場合、混入金属によって受信信号には不平衡状
態が生じる。この不平衡状態により生じた信号が発振周
波数により変調された金属検出信号であり、周波数は発
振周波数と同一である。差動増幅回路５、帯域通過フィ
ルタ６及び増幅回路７通過後、受信信号から金属検出信
号を復調する為に、同期検波回路８ａ，８ｂにより同期
検波を行う。同期検波に使用する同期信号も発振周波数
と同一であり、同期信号の位相は第１、第２の移相回路
１１ａ，１１ｂにより磁性、被磁性金属を検出するのに
適するように調整される。同期検波後の信号はアナログ
フィルタ９ａ，９ｂを通過することにより金属検出信号
のみとなり、電圧比較回路１０ａ，１０ｂにより金属の
検出結果を出力する。2. Description of the Related Art First, an outline of a conventional metal detecting device will be described with reference to FIG. In the figure, 1 is an oscillating circuit, 2 is an oscillating coil connected to the oscillating circuit, and 3a and 3b are receiving coils arranged facing or coaxial with the oscillating coil.
The magnetic fluxes a and 3b are placed in the alternating magnetic field of the oscillation coil 2, and the magnetic fluxes are equally linked by geometrically adjusting the arrangement of the two receiving coils with respect to the oscillation coil. Further, the differential voltage obtained by adjusting the differential balance of the electromotive force induced in the two receiving coils by the variable resistor 4 becomes the received signal input to the signal processing circuit. Reference numeral 5 is a differential or addition amplifier circuit, 6 is a bandpass filter having the same center frequency as the oscillation frequency, 7 is an amplifier circuit, and 100 is the same amplitude and phase as the signal that is constantly generated in the received signal. An automatic balance adjustment circuit for generating a cancel signal, 8a and 8b are synchronous detection circuits for performing synchronous detection by the first and second synchronization signals, and 9a and 9b are analog filters having the same center frequency as the metal detection signal, 10a,
Reference numeral 10b is a voltage comparison circuit for judging the magnitude of the metal detection signal demodulated by the synchronous detection circuit, and 11a and 11b are first circuits for changing the phases of the first and second synchronization signals supplied to the synchronous detection circuits 8a and 8b. , The second phase shift circuit. In the metal detection device having such a configuration, when the inspection object is passed between the oscillation coil 2 and the reception coils 3a and 3b or between the oscillation coil and the reception coil, metal is mixed in the inspection object. An unbalanced state occurs in the received signal due to the mixed metal. The signal generated by this unbalanced state is the metal detection signal modulated by the oscillation frequency, and the frequency is the same as the oscillation frequency. After passing through the differential amplifier circuit 5, the bandpass filter 6 and the amplifier circuit 7, the synchronous detection circuits 8a and 8b perform synchronous detection in order to demodulate the metal detection signal from the received signal. The synchronization signal used for the synchronous detection is also the same as the oscillation frequency, and the phase of the synchronization signal is adjusted by the first and second phase shift circuits 11a and 11b so as to be suitable for detecting the magnetic or magnetized metal. The signal after the synchronous detection passes through the analog filters 9a and 9b to become only the metal detection signal, and the voltage comparison circuits 10a and 10b output the metal detection result.
【０００３】通常、受信信号は発振コイルにより発生し
ている磁界中での受信コイルの幾何学的配置調整及びバ
ランス調整用可変抵抗の調整により、振幅はほぼ零の状
態（平衡状態）であり、上記のように金属による生じた
不平衡状態により金属検出している。しかしながら、長
期的には発振コイルや受信コイルの機械的な歪や、温度
変化による受信コイルや可変抵抗の定数の変化等により
次第に平衡状態がくずれ、受信信号中に定常的に振幅を
もつ信号（以下定常信号とする）が生じてしまう。定常
信号が大きくなってくると、アナログフィルタから出力
される検出信号のノイズが大きくなるため、検出感度が
低下してしまい、また最悪の場合には増幅回路５，７に
より信号の振幅が電源電圧で飽和し、正常な信号処理が
出来なくなり、金属検出が不可能に陥ることもある。自
動平衡調整回路１００は、上記の理由によって生じた定
常信号を平衡状態に修正する回路で、ＩＮ１，ＩＮ２の
信号より定常信号と同振幅で同位相もしくは逆位相のキ
ャンセル信号（ＯＵＴ）を生成し、差動もしくは加算増
幅回路５により、キャンセル信号と受信信号の差もしく
は和をとることで、差動もしくは加算増幅回路５の出力
では定常信号を消去することが出来る。Normally, the received signal has a substantially zero amplitude (balanced state) due to the geometrical arrangement adjustment of the receiving coil in the magnetic field generated by the oscillation coil and the adjustment of the balance adjusting variable resistor. As described above, the metal is detected by the unbalanced state caused by the metal. However, in the long term, the equilibrium state gradually collapses due to mechanical distortion of the oscillation coil and the receiving coil, changes in the constants of the receiving coil and variable resistance due to temperature changes, etc., and a signal with a steady amplitude in the received signal ( Hereinafter, a steady signal will occur). When the steady signal becomes large, the noise of the detection signal output from the analog filter becomes large, so that the detection sensitivity decreases, and in the worst case, the amplitude of the signal is changed by the amplifier circuits 5 and 7 to the power supply voltage. In some cases, it will be saturated, and normal signal processing will not be possible, and metal detection may become impossible. The automatic balance adjustment circuit 100 is a circuit that corrects a steady signal generated due to the above reason to a balanced state, and generates a cancel signal (OUT) having the same amplitude and the same phase as the steady signal from the signals IN1 and IN2. By taking the difference or the sum of the cancellation signal and the reception signal by the differential or addition amplifier circuit 5, the steady signal can be erased at the output of the differential or addition amplifier circuit 5.
【０００４】ここで上記の自動平衡調整回路１００の内
部回路構成を、図２に示し、詳細な動作について説明す
る。１０１は９０度の移相量をもつ移相回路、１０２
ａ，１０２ｂはそれぞれ０度及び９０度方向の振幅成分
を検出する同期検波回路、１０３ａ，１０３ｂは数十秒
程度の時定数をもつ積分回路、１０４ａ，１０４ｂは電
圧により増幅度を制御出来る電圧制御増幅回路、１０５
は２つの信号を加算する加算増幅回路、１０６は発振周
波数と同一の中心周波数をもつ帯域通過フィルタであ
る。Here, the internal circuit configuration of the above automatic balance adjustment circuit 100 is shown in FIG. 2, and the detailed operation will be described. 101 is a phase shift circuit having a phase shift amount of 90 degrees;
a and 102b are synchronous detection circuits for detecting amplitude components in the 0-degree and 90-degree directions, 103a and 103b are integration circuits having a time constant of several tens of seconds, and 104a and 104b are voltage controls capable of controlling the amplification degree by voltage. Amplifier circuit, 105
Is an addition amplifier circuit for adding two signals, and 106 is a bandpass filter having the same center frequency as the oscillation frequency.
【０００５】この自動平衡調整回路では、ＩＮ２の信号
を同期検波回路１０２ａ，１０２ｂにより同期検波し、
受信信号中に生じた定常信号の０度、９０度方向の振幅
成分を抽出し、さらに後段の積分回路１０３ａ，１０３
ｂにより温度等による長期的な振幅成分だけを抽出す
る。これらの振幅成分を電圧制御増幅回路１０４ａ，１
０４ｂにより、発振回路１からの０度基準信号（ＩＮ
１）と９０度移相回路１０１により９０度移相した９０
度基準信号にそれぞれ掛け合わせ、２つの出力信号を加
算増幅回路１０５により加算した後、最後に帯域通過フ
ィルタ１０６を通過させ、受信信号中の定常的に存在す
る信号（キャンセル信号：ＯＵＴ）を復元する。キャン
セル信号を差動増幅回路に入力することで、受信信号か
ら受信信号中の定常信号を削除し、差動増幅後の信号を
平衡状態にする。In this automatic balance adjustment circuit, the IN2 signal is synchronously detected by the synchronous detection circuits 102a and 102b,
Amplitude components in the 0 degree and 90 degree directions of the stationary signal generated in the received signal are extracted, and further integrated circuits 103a and 103 in the subsequent stage are extracted.
Only the long-term amplitude component due to temperature or the like is extracted by b. These amplitude components are supplied to the voltage control amplifier circuits 104a, 104a, 1
04b causes the 0 ° reference signal (IN
1) and 90 degrees shifted by 90 degrees by the 90 degree phase shift circuit 101
After multiplying each of the output reference signals by the addition reference signal, the two output signals are added by the addition amplification circuit 105, and finally passed through the bandpass filter 106 to restore a signal (cancellation signal: OUT) that is constantly present in the received signal. To do. By inputting the cancel signal to the differential amplifier circuit, the stationary signal in the received signal is deleted from the received signal, and the signal after differential amplification is brought into a balanced state.
【０００６】以上説明した動作は、図３の差動増幅回路
５→自動平衡調整回路１００→差動増幅回路５の経路で
負帰還となっているため、調整は収束方向に向い、受信
信号の平衡状態がくずれても、自動的に平衡状態に調整
される。平衡調整は積分回路１０３ａ，１０３ｂにより
長期的な振幅の変化にしか追従しないため、金属による
受信信号の振幅、位相の変化は吸収されず後段の信号処
理回路により金属検出を行うことが出来る。In the operation described above, since the negative feedback is provided in the path of the differential amplifier circuit 5 → the automatic balance adjustment circuit 100 → the differential amplifier circuit 5 of FIG. Even if the equilibrium state collapses, it is automatically adjusted to the equilibrium state. Since the balance adjustment only follows long-term changes in amplitude by the integrating circuits 103a and 103b, changes in the amplitude and phase of the received signal due to metal are not absorbed, and metal detection can be performed by the signal processing circuit in the subsequent stage.
【０００７】しかしながら、この方法では積分回路１０
３ａ，１０３ｂにより短時間には追従出来ないようにし
ているため、電源投入直後はバランスがまだ調整され
ず、数十秒程度の時間金属検出装置の動作が不安定にな
るという問題があった。また、自動平衡の調整速度は、
積分回路１０３ａ，１０３ｂを構成する部品によってき
まるためこれを自動的に変更することはできなかった。However, in this method, the integrating circuit 10
Since it is made impossible to follow in a short time by 3a and 103b, there is a problem that the balance is not adjusted immediately after the power is turned on and the operation of the metal detection device becomes unstable for a time of about several tens of seconds. Also, the adjustment speed of automatic balance is
Since it depends on the components that form the integrating circuits 103a and 103b, this cannot be changed automatically.
【０００８】[0008]
【発明が解決しようとする課題】図３に示した従来の自
動平衡調整回路では、温度等による長期的なバランスず
れのみを平衡調整するように、積分回路の構成部品を決
定しており、そのため、電源投入時等はバランス調整出
来ず、数十秒間金属検出装置の動作が不安定になるとい
う問題点があった。In the conventional automatic balance adjusting circuit shown in FIG. 3, the components of the integrating circuit are determined so that only the long-term balance deviation due to temperature etc. is balanced. However, the balance cannot be adjusted when the power is turned on and the operation of the metal detection device becomes unstable for several tens of seconds.
【０００９】本発明は、かかる点に鑑みなされたもの
で、マイコンによりバランスの調整速度を変更すること
が出来、電源投入時でも動作が不安定となることがない
金属検出装置のための自動平衡調整回路を提供すること
を目的としている。The present invention has been made in view of the above points, and an automatic balance for a metal detecting device in which the balance adjusting speed can be changed by a microcomputer and the operation does not become unstable even when the power is turned on. The purpose is to provide a regulation circuit.
【００１０】[0010]
【課題を解決するための手段】前記課題を解決する為に
本発明の金属検出装置では、従来の自動変更調整回路に
Ａ／Ｄ変換回路とＤ／Ａ変換回路と、それらとデータを
入出力するマイコンを追加し、マイコンのプログラムに
より電源投入時と通常時で演算処理方法を変えることで
バランスの平衡調整速度を変更することを可能にしたこ
とを特徴としている。In order to solve the above-mentioned problems, in the metal detector of the present invention, an A / D conversion circuit and a D / A conversion circuit are added to the conventional automatic change adjustment circuit, and data is input / output to / from them. It is possible to change the balance adjustment speed by adding a new microcomputer and changing the arithmetic processing method at power-on and normal time by the program of the microcomputer.
【００１１】[0011]
【作用】Ａ／Ｄ変換回路により受信信号の振幅値をマイ
コンに入力し、マイコンからＤ／Ａ変換回路を使ってキ
ャンセル信号の振幅を制御することにより、電源投入時
は短時間で平衡状態に調整し、通常動作時では温度等に
よる長期的なバランスずれにしか対応しないように、調
整速度をプログラムにより変更出来るようにした。[Function] By inputting the amplitude value of the received signal to the microcomputer by the A / D conversion circuit and controlling the amplitude of the cancel signal by the microcomputer using the D / A conversion circuit, the equilibrium state is achieved in a short time when the power is turned on. Adjustment was made so that the adjustment speed could be changed by a program so that it would only respond to long-term balance deviations due to temperature etc. during normal operation.
【００１２】[0012]
【実施例】図１はこの発明の一実施例を示すブロック図
で、符号１，２，３ａ，３ｂ，４，５，７及び１０１，
１０２ａ，１０２ｂ，１０４ａ，１０４ｂ，１０５，１
０６は図２と同じものである。１０７ａ，１０７ｂは被
同期検波信号の高調波成分を除去するための低域通過フ
ィルタ、１０８ａ，１０８ｂは受信信号の振幅成分をデ
ジタル値に変換するＡ／Ｄ変換回路、１０９はＡ／Ｄ変
換回路からのデータを入力し、Ｄ／Ａ変換回路にデータ
を出力するマイコン、１１０ａ，１１０ｂはマイコンか
らのデジタル値に応じ直流電圧を出力するＤ／Ａ変換回
路である。1 is a block diagram showing an embodiment of the present invention, in which reference numerals 1, 2, 3a, 3b, 4, 5, 7 and 101,
102a, 102b, 104a, 104b, 105, 1
06 is the same as in FIG. 107a and 107b are low-pass filters for removing harmonic components of the synchronized detection signal, 108a and 108b are A / D conversion circuits for converting the amplitude components of the received signal into digital values, and 109 is an A / D conversion circuit. Microcomputers that input data from the microcomputer and output data to the D / A conversion circuit, and 110a and 110b are D / A conversion circuits that output a DC voltage according to the digital value from the microcomputer.
【００１３】以下に実施例における自動平衡回路の動作
について説明する。ＩＮ２（増幅後の受信信号）の信号
を同期検波回路１０２ａ，１０２ｂにより同期検波し、
受信信号中に生じた定常信号の０度、９０度方向の振幅
成分を抽出、後段の低域通過フィルタ１０７ａ，１０７
ｂにより高調波成分を除去し、振幅成分だけを抽出す
る。これらの振幅成分をＡ／Ｄ変換回路１０８ａ，１０
８ｂにより、デジタル値としてマイコン１０９に出力す
る。マイコンでは、入力したデジタル値に対し種々の演
算を行い、その結果をデジタル値としてＤ／Ａ変換回路
１１０ａ，１１０ｂに出力する。Ｄ／Ａ変換回路１１０
ａ，１１０ｂはデジタル値に基づいた電圧を、電圧制御
増幅回路に出力する。電圧制御増幅回路１０４ａ，１０
４ｂにより、発振回路１からの０度基準信号（ＩＮ１）
と９０度移相回路１０１により９０度移相した９０度基
準信号にそれぞれ掛け合わせ、２つの出力信号を加算増
幅回路１０５により加算した後、最後に帯域通過フィル
タ１０６を通過させ、受信信号中の定常的に存在する信
号を消去するためのキャンセル信号（ＯＵＴ）を生成す
る。The operation of the automatic balancing circuit in the embodiment will be described below. The signal of IN2 (received signal after amplification) is synchronously detected by the synchronous detection circuits 102a and 102b,
Amplitude components in the 0 ° and 90 ° directions of the stationary signal generated in the received signal are extracted, and low-pass filters 107a and 107 in the subsequent stage are extracted.
The harmonic component is removed by b, and only the amplitude component is extracted. These amplitude components are converted into A / D conversion circuits 108a and 10a.
It is output to the microcomputer 109 as a digital value by 8b. The microcomputer performs various calculations on the input digital value and outputs the result as a digital value to the D / A conversion circuits 110a and 110b. D / A conversion circuit 110
a and 110b output the voltage based on the digital value to the voltage control amplifier circuit. Voltage control amplifier circuits 104a, 10
0b reference signal (IN1) from the oscillation circuit 1 by 4b
And the 90-degree phase-shifted signal by the 90-degree phase-shifting circuit 101 are respectively multiplied, two output signals are added by the addition amplification circuit 105, and finally passed through the band-pass filter 106 to obtain a signal in the received signal. A cancel signal (OUT) for erasing a signal that is present steadily is generated.
【００１４】マイコンでは、通常、Ａ／Ｄ変換回路１０
８ａ，１０８ｂから入力したデジタル値に応じたデジタ
ル値をＤ／Ａ変換回路１１０ａ，１１０ｂに出力し、差
動増幅回路５→自動平衡調整回路１００→差動増幅回路
５の経路で負帰還になるようにしているため、調整は収
束方向に向い、受信信号の平衡状態がくずれても、自動
的に平衡状態に調整される。ただし、従来の技術では積
分回路１０３ａ，１０３ｂにより調整速度が決定されて
いたが、本発明ではマイコンでのデジタル演算処理が積
分回路の代わりとなるため、マイコンのプログラムによ
り調整速度を変更することが出来る。マイコンで行う演
算は、移動平均等のデジタルフィルタリング処理であ
り、例えば、電源投入時は移動平均点数を少なく、通常
検査時では移動平均点数を多くすることで、応答速度即
ち調整速度をプログラムで自由に変更することが出来
る。In the microcomputer, the A / D conversion circuit 10 is usually used.
A digital value corresponding to the digital value input from 8a, 108b is output to the D / A conversion circuits 110a, 110b, and negative feedback is provided in the path of the differential amplifier circuit 5 → the automatic balance adjustment circuit 100 → the differential amplifier circuit 5. Therefore, the adjustment is directed to the convergence direction, and even if the balanced state of the received signal is lost, the balanced state is automatically adjusted. However, in the conventional technique, the adjusting speed is determined by the integrating circuits 103a and 103b, but in the present invention, the adjusting speed can be changed by a program of the microcomputer because the digital arithmetic processing in the microcomputer replaces the integrating circuit. I can. The calculation performed by the microcomputer is a digital filtering process such as moving average. For example, the response speed, that is, the adjustment speed can be freely programmed by increasing the moving average score during power-on and decreasing the moving average score during normal inspection. Can be changed to
【００１５】[0015]
【発明の効果】この発明は、以上詳細に説明したよう
に、従来の自動変更調整回路に、Ａ／Ｄ変換回路とＤ／
Ａ変換回路と、Ａ／Ｄ、Ｄ／Ａ変換回路に対しデータを
入出力し演算するマイコンを追加することで、自動平衡
調整回路を構成する素子の交換等をせずに、自動平衡の
調整速度を変更することで、金属検出機装置が電源投入
後即時安定動作が可能となるすぐれた効果がある。As described in detail above, the present invention provides a conventional automatic change adjustment circuit with an A / D conversion circuit and a D / D conversion circuit.
By adding an A conversion circuit and a microcomputer that inputs and outputs data to and from the A / D and D / A conversion circuits, the automatic balance adjustment is performed without replacing the elements that make up the automatic balance adjustment circuit. By changing the speed, there is an excellent effect that the metal detector device can be stably operated immediately after the power is turned on.
【図１】この発明の一実施例を示す構成図。FIG. 1 is a configuration diagram showing an embodiment of the present invention.
【図２】従来の自動平衡調整回路の例を示す構成図。FIG. 2 is a configuration diagram showing an example of a conventional automatic balance adjustment circuit.
【図３】従来の金属検出装置の一例を示す構成図。FIG. 3 is a configuration diagram showing an example of a conventional metal detection device.
１ 発振回路 ２ 発振コイル ３ａ，３ｂ 受信コイル ４ 差動バランス調整用の可変抵抗 ５ 差動もしくは加算増幅回路 ６ 帯域通過フィルタ ７ 増幅回路 ８ａ，８ｂ 同期検波回路 ９ａ，９ｂ アナログフィルタ １０ａ，１０ｂ 電圧比較回路 １１ａ，１１ｂ 第１、第２の移相回路 １００ 自動平衡調整回路 １０１ ９０度移相回路 １０２ａ，１０２ｂ 同期検波回路 １０３ａ，１０３ｂ 積分回路 １０４ａ，１０４ｂ 電圧制御増幅回路 １０５ 加算増幅回路 １０６ 帯域通過フィルタ １０７ａ，１０７ｂ 低域通過フィルタ １０８ａ，１０８ｂ Ａ／Ｄ変換回路 １０９ マイコン １１０ａ，１１０ｂ Ｄ／Ａ変換回路 1 Oscillation circuit 2 Oscillation coil 3a, 3b Reception coil 4 Variable resistance for differential balance adjustment 5 Differential or summing amplification circuit 6 Band pass filter 7 Amplification circuit 8a, 8b Synchronous detection circuit 9a, 9b Analog filter 10a, 10b Voltage comparison Circuits 11a, 11b First and second phase shift circuits 100 Automatic balance adjustment circuit 101 90 degree phase shift circuits 102a, 102b Synchronous detection circuits 103a, 103b Integration circuits 104a, 104b Voltage control amplification circuits 105 Summing amplification circuits 106 Band pass filters 107a, 107b Low-pass filter 108a, 108b A / D conversion circuit 109 Microcomputer 110a, 110b D / A conversion circuit
Claims (1)
磁束の変化を検出する受信コイルを有し、受信コイルか
らの受信信号を自動平衡調整回路から発生するキャンセ
ル信号により、平衡状態にさせ、発振コイルと受信コイ
ル間に被検査体を通過させた時、平衡がくずれるか否か
により、当該被検査体中の金属混入の有無を検知する形
式の金属検出装置において、受信信号の振幅成分を抽出
する同期検波回路と、高調波成分を除去し振幅成分だけ
を取り出す低域通過フィルタと、受信信号の振幅の大き
さを測定するためのＡ／Ｄ変換回路と、マイコンからの
設定により電圧を出力するＤ／Ａ変換回路と、Ｄ／Ａ変
換回路からの電圧により振幅を制御出来る電圧制御増幅
回路と、Ａ／Ｄ変換回路からのデータの入力、データの
演算、Ｄ／Ａ変換回路へのデータの出力を行うマイコン
を具備し、同期検波回路により検出した受信信号の振幅
を、低域通過フィルタを通した後、Ａ／Ｄ変換回路によ
り測定し、その振幅データをマイコンが入力し、種々の
演算を行った後、その結果に応じたデータをマイコンか
らＤ／Ａ変換回路に出力し、Ｄ／Ａ変換回路から出力さ
れる電圧値により電圧制御増幅回路を操作することによ
り、キャンセル信号を生成したことを特徴とする自動平
衡調整回路。1. An oscillating coil for generating an alternating magnetic field and a receiving coil for detecting a change in its magnetic flux, wherein a receiving signal from the receiving coil is brought into a balanced state by a cancel signal generated by an automatic balance adjusting circuit and oscillated. Extracts the amplitude component of the received signal in a metal detection device of the type that detects the presence or absence of metal contamination in the test object depending on whether the balance is broken when the test object is passed between the coil and the receiving coil. Synchronous detection circuit, low-pass filter that removes harmonic components and extracts only amplitude components, A / D conversion circuit for measuring the magnitude of amplitude of received signal, and outputs voltage by setting from microcomputer D / A converter circuit, a voltage control amplifier circuit whose amplitude can be controlled by the voltage from the D / A converter circuit, data input from the A / D converter circuit, data calculation, and D / A conversion circuit. Equipped with a microcomputer that outputs data to the path, the amplitude of the received signal detected by the synchronous detection circuit is measured by the A / D conversion circuit after passing through a low pass filter, and the amplitude data is input to the microcomputer. Then, after performing various calculations, data corresponding to the result is output from the microcomputer to the D / A conversion circuit, and the voltage control amplifier circuit is operated by the voltage value output from the D / A conversion circuit. An automatic balance adjustment circuit characterized by generating a cancel signal.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP7251895A JPH08248143A (en) | 1995-03-07 | 1995-03-07 | Automatic equilibrium adjusting circuit of metal detection apparatus |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP7251895A JPH08248143A (en) | 1995-03-07 | 1995-03-07 | Automatic equilibrium adjusting circuit of metal detection apparatus |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH08248143A true JPH08248143A (en) | 1996-09-27 |
Family
ID=13491636
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP7251895A Pending JPH08248143A (en) | 1995-03-07 | 1995-03-07 | Automatic equilibrium adjusting circuit of metal detection apparatus |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH08248143A (en) |
-
1995
- 1995-03-07 JP JP7251895A patent/JPH08248143A/en active Pending
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4326166A (en) | Correcting circuit for differential pick-up, comprising digital means | |
| US6672159B2 (en) | Method for adjusting the phase-locking loop of an electronic evaluation device and corresponding electronic evaluation device | |
| JPH08248143A (en) | Automatic equilibrium adjusting circuit of metal detection apparatus | |
| JPH08248144A (en) | Automatic equiliblium adjusting circuit of metal detection apparatus | |
| JP2020190547A (en) | Method for operating metal detector, and metal detector | |
| JPH0854475A (en) | Metal detector | |
| JPH0792274A (en) | Automatic balance-adjusting circuit of metal detector | |
| JP2001296342A (en) | Differential magnetic sensor | |
| JP3324840B2 (en) | Metal detector | |
| JPS6355456A (en) | Flaw discriminating device for eddy current flaw detector | |
| JP3088529B2 (en) | Metal detector | |
| JPS6314904B2 (en) | ||
| JPS6039552A (en) | Eddy current flaw detector | |
| JPH1183616A (en) | Necessary vibration component extracting vibration measuring equipment | |
| JPH07229874A (en) | Eddy current flaw detection device | |
| JPS60253967A (en) | Eddy current flaw detecting device | |
| JPS5836755B2 (en) | How to detect contaminated metals | |
| JPH0344552A (en) | Multichannel eddy current test equipment | |
| JPH05232247A (en) | Metal detector | |
| JPH05180949A (en) | Metal detecting apparatus | |
| JP3500004B2 (en) | Metal detector | |
| JPH06313798A (en) | Detecting device of metal | |
| JPH07311228A (en) | Phase-difference detecting circuit | |
| JPS6331003Y2 (en) | ||
| JPS59166857A (en) | Signal processing circuit of multi-probe and multi-frequency eddy current test equipment |