JP2007240286A - Measuring method and measuring instrument - Google Patents

Measuring method and measuring instrument Download PDF

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JP2007240286A
JP2007240286A JP2006061953A JP2006061953A JP2007240286A JP 2007240286 A JP2007240286 A JP 2007240286A JP 2006061953 A JP2006061953 A JP 2006061953A JP 2006061953 A JP2006061953 A JP 2006061953A JP 2007240286 A JP2007240286 A JP 2007240286A
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signal
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switching
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Junji Kuwabara
淳司 桑原
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Yokogawa Electric Corp
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<P>PROBLEM TO BE SOLVED: To provide a measuring method and measuring instrument capable of reducing influence of characteristic change such as fluctuation in temperature without improving the accuracy and stability of a driving signal generating section and signal detecting section. <P>SOLUTION: The measuring method for supplying a driving signal to a sensor and detecting a sensor output signal corresponding to the physical quantity change of a measured object comprises a switching step of selectively switching between the driving signal and the sensor output signal, a first arithmetic step of detecting the signal level of the sensor output signal selected in the switch step, a second arithmetic step of detecting the signal level of the driving signal selected in the switch step, and a corrective arithmetic step of acquiring a measuring output signal corrected using outputs of the first and second arithmetic steps. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

本発明は、センサに駆動信号を供給するとともに測定対象の物理量変化に対応したセンサ出力信号を検出する計測方法および計測装置に関し、特に、測定に際し温度変動等の環境変動による特性変化を低減することができる計測方法および計測装置に関するものである。   The present invention relates to a measurement method and a measurement apparatus for supplying a drive signal to a sensor and detecting a sensor output signal corresponding to a physical quantity change of a measurement target, and in particular, to reduce characteristic changes due to environmental fluctuations such as temperature fluctuations during measurement. The present invention relates to a measuring method and a measuring apparatus that can perform the above.

図4は従来の計測装置の一例を示したブロック図であり、測定に際しセンサに駆動信号の供給が必要な回路の構成例を示している。   FIG. 4 is a block diagram showing an example of a conventional measuring apparatus, and shows a configuration example of a circuit that requires a drive signal to be supplied to a sensor during measurement.

図4(a)に示す回路例では、駆動信号生成部102はセンサ101を駆動するための駆動信号を生成してセンサ101に供給する。また、安定したセンサ出力を得るために、駆動信号のフィードバックループを有し、安定した駆動信号を出力している。得られたセンサ出力信号は信号検出部103により適切な処理が行われ、計測結果を得る。   In the circuit example illustrated in FIG. 4A, the drive signal generation unit 102 generates a drive signal for driving the sensor 101 and supplies the drive signal to the sensor 101. In addition, in order to obtain a stable sensor output, a drive signal feedback loop is provided to output a stable drive signal. The obtained sensor output signal is appropriately processed by the signal detection unit 103 to obtain a measurement result.

図4(b)に示す回路例では、駆動信号生成部104は駆動信号を生成しセンサ101に供給する。駆動信号生成部104は駆動信号のフィードバックループを有しないが、生成された駆動信号は信号検出部106を介して補正演算部107に入力される。センサ101から出力されるセンサ出力信号は信号検出部105を介して補正演算部107に入力される。補正演算部107はセンサ出力信号および駆動信号の検出値を用いて駆動信号変動の補正等の処理を行い、駆動信号変動の影響を除去した計測結果を得る。   In the circuit example illustrated in FIG. 4B, the drive signal generation unit 104 generates a drive signal and supplies it to the sensor 101. The drive signal generation unit 104 does not have a drive signal feedback loop, but the generated drive signal is input to the correction calculation unit 107 via the signal detection unit 106. A sensor output signal output from the sensor 101 is input to the correction calculation unit 107 via the signal detection unit 105. The correction calculation unit 107 performs processing such as correction of drive signal fluctuation using the sensor output signal and the detected value of the drive signal, and obtains a measurement result from which the influence of the drive signal fluctuation is removed.

特開平9−184883号公報Japanese Patent Laid-Open No. 9-184883

しかしながら、図4(a)の回路例においては、測定精度を向上するために駆動信号生成部102及び信号検出部103の精度や安定性を向上する必要があり、また温度変化に対する補正機能が必要となる。また、図4(b)の回路例においては、駆動信号生成部104については精度を必要としないが、信号検出部105および106の精度や安定性を向上させる必要がある。また、温度変化等の要因により信号検出部105および106の特性が変化したとき、その特性変化に差異がある場合には、計測結果に誤差が発生する。   However, in the circuit example of FIG. 4A, it is necessary to improve the accuracy and stability of the drive signal generation unit 102 and the signal detection unit 103 in order to improve the measurement accuracy, and a correction function for temperature change is necessary. It becomes. In the circuit example of FIG. 4B, the drive signal generation unit 104 does not require accuracy, but the accuracy and stability of the signal detection units 105 and 106 need to be improved. In addition, when the characteristics of the signal detectors 105 and 106 change due to a change in temperature or the like, if there is a difference in the characteristics change, an error occurs in the measurement result.

図5は図4(b)の回路例において信号検出部105および106のゲインが計測結果に与える影響の説明図である。センサ特性及び信号検出部特性がリニアである場合を例に挙げると、駆動信号生成部104の変動を除去するために、補正演算部では以下に示す除算処理を行う。
計測結果=(信号検出部105出力/A)/(信号検出部106出力/B)
=センサの真の計測値
ここで、Aは信号検出部105のゲイン、Bは信号検出部106のゲインである。
FIG. 5 is an explanatory diagram of the influence of the gains of the signal detection units 105 and 106 on the measurement result in the circuit example of FIG. Taking the case where the sensor characteristic and the signal detection unit characteristic are linear as an example, in order to remove the fluctuation of the drive signal generation unit 104, the correction calculation unit performs the following division processing.
Measurement result = (signal detection unit 105 output / A) / (signal detection unit 106 output / B)
= True measured value of sensor Here, A is the gain of the signal detection unit 105, and B is the gain of the signal detection unit 106.

温度変動等の理由により、信号検出部105および106のゲインがそれぞれA×α、B×βに変動したとすると、得られる計測結果は
計測結果=(信号検出部105出力/A×α)/(信号検出部106出力/B×β)
=(信号検出部105出力/A)/(信号検出部106出力/B)×(β/α)
=センサの真の計測値×(β/α)
となり、信号検出部105および106のゲイン変動(β/α)による測定誤差が生じてしまう。
If the gains of the signal detectors 105 and 106 change to A × α and B × β for reasons such as temperature fluctuations, the measurement result obtained is: measurement result = (signal detector 105 output / A × α) / (Signal detection unit 106 output / B × β)
= (Signal detection unit 105 output / A) / (Signal detection unit 106 output / B) × (β / α)
= True measured value of sensor x (β / α)
Thus, a measurement error due to the gain fluctuation (β / α) of the signal detectors 105 and 106 occurs.

本発明は、上記のような従来の欠点をなくし、駆動信号生成部および信号検出部の精度や安定性を向上させることなく、温度変動等の特性変化による影響を低減することができる計測方法および計測装置を実現することを目的としたものである。   The present invention eliminates the conventional drawbacks as described above, and can improve the accuracy and stability of the drive signal generation unit and the signal detection unit, and can reduce the influence caused by characteristic changes such as temperature fluctuations and the like. The purpose is to realize a measuring device.

上記のような目的を達成するために、本発明の請求項1では、センサに駆動信号を供給するとともに測定対象の物理量変化に対応したセンサ出力信号を検出する計測方法において、
前記駆動信号および前記センサ出力信号を選択的に切り替える切替ステップと、
前記切替ステップにより選択された前記センサ出力信号の信号レベルを検出する第1の演算ステップと、
前記切替ステップにより選択された前記駆動信号の信号レベルを検出する第2の演算ステップと、
前記第1および第2の演算ステップの出力を利用して補正された測定出力信号を得る補正演算ステップと、
を有することを特徴とする。
In order to achieve the above object, according to claim 1 of the present invention, in a measurement method for supplying a drive signal to a sensor and detecting a sensor output signal corresponding to a physical quantity change of a measurement target,
A switching step of selectively switching the drive signal and the sensor output signal;
A first calculation step of detecting a signal level of the sensor output signal selected by the switching step;
A second calculation step of detecting a signal level of the drive signal selected by the switching step;
A correction calculation step for obtaining a corrected measurement output signal using the outputs of the first and second calculation steps;
It is characterized by having.

請求項2では、請求項1に記載の計測方法において、前記補正演算ステップは、前記第1の演算ステップの出力を前記第2の演算ステップの出力で除算することを特徴とする。   According to a second aspect of the present invention, in the measurement method according to the first aspect, the correction calculation step divides the output of the first calculation step by the output of the second calculation step.

請求項3では、請求項1または2に記載の計測方法において、前記第1および第2の演算ステップは、切替ステップに同期して選択的に実施されることを特徴とする。   According to a third aspect of the present invention, in the measurement method according to the first or second aspect, the first and second calculation steps are selectively performed in synchronization with the switching step.

請求項4では、センサに駆動信号を供給するとともに測定対象の物理量変化に対応したセンサ出力信号を検出する計測装置において、
前記駆動信号および前記センサ出力信号が入力され、いずれか一方の信号を選択的に切り替えて出力する信号切替部と、
この信号切替部から出力される信号の信号レベルを検出する信号検出部と、
前記信号検出部から出力された前記駆動信号およびセンサ出力信号の演算結果を利用して補正された測定出力信号を発生する補正演算部と、
を有することを特徴とする。
According to a fourth aspect of the present invention, in the measuring device for supplying the driving signal to the sensor and detecting the sensor output signal corresponding to the physical quantity change of the measurement target,
The drive signal and the sensor output signal are input, and a signal switching unit that selectively switches and outputs one of the signals;
A signal detection unit for detecting the signal level of the signal output from the signal switching unit;
A correction calculation unit that generates a measurement output signal corrected using the calculation result of the drive signal and sensor output signal output from the signal detection unit;
It is characterized by having.

請求項5では、請求項4に記載の計測装置において、前記補正演算部は、前記センサ出力信号に応じた演算出力を前記駆動信号に応じた演算出力で除算して補正演算を行うことを特徴とする。   According to a fifth aspect of the present invention, in the measurement apparatus according to the fourth aspect, the correction calculation unit performs a correction calculation by dividing a calculation output corresponding to the sensor output signal by a calculation output corresponding to the drive signal. And

請求項6では、請求項4または5に記載の計測装置において、前記補正演算部は、前記信号切替部の切替動作に同期して前記駆動信号および前記センサ出力信号の演算結果を取り込むことを特徴とする。   According to a sixth aspect of the present invention, in the measurement apparatus according to the fourth or fifth aspect, the correction calculation unit captures calculation results of the drive signal and the sensor output signal in synchronization with a switching operation of the signal switching unit. And

請求項7では、請求項4乃至6のいずれかに記載の計測装置において、前記センサは駆動電圧の供給を受けて燃料タンク内の液面レベルに応じた電流信号を出力する静電容量式のタンクユニットであり、
前記駆動電圧を電流信号に変換して前記信号切替部に出力するレベル変換回路を有し、
前記信号検出部は前記タンクユニットから出力される電流信号または前記レベル変換回路から出力される電流信号の信号レベルを検出する電流振幅検出回路であることを特徴とする。
According to a seventh aspect of the present invention, in the measuring device according to any one of the fourth to sixth aspects, the sensor is an electrostatic capacitance type that outputs a current signal corresponding to a liquid level in the fuel tank in response to the supply of the driving voltage. Tank unit,
A level conversion circuit that converts the drive voltage into a current signal and outputs the current signal to the signal switching unit;
The signal detection unit is a current amplitude detection circuit that detects a signal level of a current signal output from the tank unit or a current signal output from the level conversion circuit.

このように、センサ出力信号および駆動信号の信号レベルの検出を行う信号検出部を共通化することにより、補正演算部において信号検出部が有する特性変動を取り除くことができ、駆動信号生成部および信号検出部の精度や安定性を向上させることなく、温度変動等の特性変化による影響を低減することができる計測方法および計測装置を実現することができる。   In this way, by sharing the signal detection unit that detects the signal level of the sensor output signal and the drive signal, characteristic correction of the signal detection unit in the correction calculation unit can be removed, and the drive signal generation unit and the signal A measurement method and a measurement apparatus that can reduce the influence of characteristic changes such as temperature fluctuations can be realized without improving the accuracy and stability of the detection unit.

以下、図面を用いて本発明の計測方法および計測装置を説明する。   Hereinafter, the measurement method and the measurement apparatus of the present invention will be described with reference to the drawings.

図1は本発明による計測装置の一実施例を示すブロック図である。駆動信号生成部2はセンサ1に供給する駆動信号S1を生成する。駆動信号S1はセンサ1に供給されるとともに、信号切替部3に入力される。センサ1は駆動信号S1の供給を受けて測定対象の物理量変化に対応したセンサ出力信号S2を発生する。信号切替部3は入力された駆動信号S1とセンサ出力信号S2のいずれか一方を選択的に切り替えて信号検出部4に出力する。信号切替部4は、入力された信号の信号レベルの検出を行う。補正演算部5はセンサ出力信号S2検出値および駆動信号S1検出値を用いて駆動信号変動の補正等の処理を行い計測結果を得る。   FIG. 1 is a block diagram showing an embodiment of a measuring apparatus according to the present invention. The drive signal generator 2 generates a drive signal S1 to be supplied to the sensor 1. The drive signal S1 is supplied to the sensor 1 and input to the signal switching unit 3. The sensor 1 receives the supply of the drive signal S1 and generates a sensor output signal S2 corresponding to a change in the physical quantity to be measured. The signal switching unit 3 selectively switches one of the input drive signal S1 and sensor output signal S2 and outputs it to the signal detection unit 4. The signal switching unit 4 detects the signal level of the input signal. The correction calculation unit 5 performs processing such as correction of drive signal fluctuation using the sensor output signal S2 detection value and the drive signal S1 detection value to obtain a measurement result.

前記信号切替部3での信号切替は、補正演算部5において駆動信号S1とセンサ出力信号S2の両方を利用する関係上、必要に応じて(たとえば一定時間ごとに)自動的に行われる。信号切替部3からは信号の切替状態を示す制御信号S3が補正演算部5に出力され、信号切替と同期した信号の取り込みを行うために利用される。   The signal switching in the signal switching unit 3 is automatically performed as necessary (for example, at regular intervals) because the correction calculation unit 5 uses both the drive signal S1 and the sensor output signal S2. A control signal S3 indicating a signal switching state is output from the signal switching unit 3 to the correction calculation unit 5, and is used for capturing a signal synchronized with the signal switching.

一般的に、駆動信号S1とセンサ出力信号S2は同種の信号であることが多い。このとき、駆動信号S1とセンサ出力信号S2の信号レベルの検出を行う信号検出部4を共有することにより、信号検出部4が有する温度変化等に伴う特性変動(たとえばゲイン変動αとする)は、センサ出力信号S2検出値および駆動信号S1検出値の両方に乗ぜられる。   In general, the drive signal S1 and the sensor output signal S2 are often the same type of signal. At this time, by sharing the signal detection unit 4 that detects the signal levels of the drive signal S1 and the sensor output signal S2, a characteristic variation (for example, gain variation α) associated with a temperature change or the like of the signal detection unit 4 is reduced. The sensor output signal S2 detection value and the drive signal S1 detection value are both multiplied.

補正演算部5では、駆動信号S1の変動による計測値を除去するため、一般には除算処理が行われる。この除算処理により駆動信号生成部2の変動が取り除かれ、安定した計測結果を得ることができる。   In the correction calculation unit 5, a division process is generally performed in order to remove the measurement value due to the fluctuation of the drive signal S1. By this division processing, fluctuations in the drive signal generation unit 2 are removed, and a stable measurement result can be obtained.

このとき、信号検出部4におけるゲイン変動αはセンサ出力信号S2検出値および駆動信号S1検出値の両方に乗ぜられているので、除算処理によりα/α=1となり、ゲイン変動αによる変動が相殺され、計測結果に与える影響を除去することができる。また、これにより、駆動信号生成部2や信号検出部4を高精度化しなくても、高精度の測定を行うことができるという利点がある。   At this time, since the gain fluctuation α in the signal detection unit 4 is multiplied by both the sensor output signal S2 detection value and the drive signal S1 detection value, α / α = 1 is obtained by the division process, and the fluctuation due to the gain fluctuation α is canceled out. Thus, the influence on the measurement result can be removed. This also has the advantage that highly accurate measurement can be performed without increasing the accuracy of the drive signal generator 2 and the signal detector 4.

なお、本実施例では信号切替部3が自走している場合を説明したが、補正演算部5の補正演算に合わせて信号切替部3の信号切替を制御する構成としてもよい。その場合には、補正演算部5に切替制御部を設け、補正演算部5から信号切替部3へ切替信号を出力する。   In the present embodiment, the case where the signal switching unit 3 is self-running has been described. However, the signal switching of the signal switching unit 3 may be controlled in accordance with the correction calculation of the correction calculation unit 5. In that case, a switching control unit is provided in the correction calculation unit 5, and a switching signal is output from the correction calculation unit 5 to the signal switching unit 3.

図2は本発明による計測装置の他の実施例を示すブロック図であり、航空機などの燃料タンク内の燃料の液面レベルを測定する計測装置に適用した一例を示したものである。   FIG. 2 is a block diagram showing another embodiment of the measuring apparatus according to the present invention, and shows an example applied to a measuring apparatus for measuring the level of fuel in a fuel tank such as an aircraft.

タンクユニット11は燃料タンク内の燃料の液面レベルを静電容量変化として検出するセンサであり、センサ出力信号S12は電流信号である。正弦波発生回路12はタンクユニットに駆動信号として供給する正弦波電圧信号S11を生成する。タンクユニット11の交流インピーダンスはωCで示され(ω=2πf、Cは測定すべき静電容量、fは正弦波電圧信号S11の周波数)、信号S11で正弦波振幅V(rms)を印加した場合の電流はI(rms)=V/(ωC)となる。これよりC=V/(ωI)となり、静電容量を測定することができる。静電容量から液面レベルへの換算はタンクユニットによって規定されている換算方法による。   The tank unit 11 is a sensor that detects the liquid level of the fuel in the fuel tank as a change in capacitance, and the sensor output signal S12 is a current signal. The sine wave generation circuit 12 generates a sine wave voltage signal S11 to be supplied as a drive signal to the tank unit. The AC impedance of the tank unit 11 is indicated by ωC (ω = 2πf, C is the capacitance to be measured, f is the frequency of the sine wave voltage signal S11), and the sine wave amplitude V (rms) is applied by the signal S11 The current of I (rms) = V / (ωC). Thus, C = V / (ωI), and the capacitance can be measured. Conversion from the capacitance to the liquid level is based on a conversion method defined by the tank unit.

ここで、正弦波電圧信号S11の正弦波振幅Vには、正弦波発生回路12自体の係数が含まれているため、以下のように表すことができる。
V=γ×V´
V´は正弦波発生回路12の真の出力電圧、γは正弦波発生回路12の係数である。
Here, the sine wave amplitude V of the sine wave voltage signal S11 includes the coefficient of the sine wave generation circuit 12 itself, and therefore can be expressed as follows.
V = γ × V ′
V ′ is a true output voltage of the sine wave generation circuit 12, and γ is a coefficient of the sine wave generation circuit 12.

正弦波電圧信号S11はタンクユニット11に供給されるとともにレベル変換回路13に信号S11のレベル検出信号S14(電圧)として入力される。   The sine wave voltage signal S11 is supplied to the tank unit 11 and input to the level conversion circuit 13 as a level detection signal S14 (voltage) of the signal S11.

レベル変換回路13は入力されたレベル検出信号S14を電流信号S15に変換する。本実施例ではタンクユニットのセンサ出力信号S12が電流信号であるのに対し、駆動信号S11は電圧であるため、レベル変換回路13において電圧−電流変換を行い両信号の種類をそろえる。レベル変換回路13は駆動信号S11とセンサ出力信号S12の種類が異なるときに設けられる変換回路である。   The level conversion circuit 13 converts the input level detection signal S14 into a current signal S15. In the present embodiment, the sensor output signal S12 of the tank unit is a current signal, whereas the drive signal S11 is a voltage. Therefore, the level conversion circuit 13 performs voltage-current conversion to align both signals. The level conversion circuit 13 is a conversion circuit provided when the types of the drive signal S11 and the sensor output signal S12 are different.

タンクユニット11からのセンサ出力信号S12とレベル変換回路13で変換されたレベル検出信号S15は、信号切替部14で選択的に切り替えられて電流振幅検出回路15に取り込まれる。   The sensor output signal S12 from the tank unit 11 and the level detection signal S15 converted by the level conversion circuit 13 are selectively switched by the signal switching unit 14 and taken into the current amplitude detection circuit 15.

電流振幅検出回路15は信号切替部14から入力される電流信号の信号レベルに対応するA/D値を求め、制御演算部16に出力する。   The current amplitude detection circuit 15 calculates an A / D value corresponding to the signal level of the current signal input from the signal switching unit 14 and outputs the A / D value to the control calculation unit 16.

制御演算回路16は補正演算部161と、切替信号S13を用いて信号切替部14を制御する切替制御部162を有し、電流振幅検出回路15においてセンサ出力信号S12とレベル検出信号S15のどちらの信号の信号レベルを検出するかを決定する。たとえば、まずレベル検出信号S15を電流振幅回路15に出力してA/D値を求め、その後電流振幅回路15への出力をセンサ出力信号S12に切り替えてそのA/D値を求める。得られたセンサ出力信号S12とレベル検出信号S15のA/D値をもとに補正演算処理および表示データ生成処理を行い、結果を表示回路17に出力する。また、切替制御部162の有する切替情報は、補正演算部161において信号切替と同期した信号の取り込みを行うために利用される。   The control calculation circuit 16 includes a correction calculation unit 161 and a switching control unit 162 that controls the signal switching unit 14 using the switching signal S13. In the current amplitude detection circuit 15, either the sensor output signal S12 or the level detection signal S15 is selected. Decide whether to detect the signal level of the signal. For example, the level detection signal S15 is first output to the current amplitude circuit 15 to obtain an A / D value, and then the output to the current amplitude circuit 15 is switched to the sensor output signal S12 to obtain the A / D value. Based on the obtained A / D values of the sensor output signal S12 and the level detection signal S15, correction calculation processing and display data generation processing are performed, and the result is output to the display circuit 17. In addition, the switching information of the switching control unit 162 is used by the correction calculation unit 161 to capture a signal synchronized with signal switching.

電流振幅検出回路15のA/D値出力は以下の式で示すことができる。
AD(FB)=β×(γ×V´)/ω
AD(MEAS)=β×(γ×V´)/(ω×C)
ここで、AD(FB)はレベル検出信号S15のA/D値、AD(MEAS)はセンサ出力信号S12のA/D値、βは電流振幅検出回路15の変換係数、Cはタンクユニット11の静電容量、ωは正弦波発生回路12の発振周波数f×2πである。
The A / D value output of the current amplitude detection circuit 15 can be expressed by the following equation.
AD (FB) = β × (γ × V ′) / ω
AD (MEAS) = β × (γ × V ′) / (ω × C)
Here, AD (FB) is the A / D value of the level detection signal S15, AD (MEAS) is the A / D value of the sensor output signal S12, β is the conversion coefficient of the current amplitude detection circuit 15, and C is the tank unit 11. The capacitance, ω, is the oscillation frequency f × 2π of the sine wave generation circuit 12.

制御演算回路16ではAD(FB)/AD(MEAS)を計測結果RESULTとする補正演算を行う。
RESULT=AD(FB)/AD(MEAS)
={β×(γ×V´)/ω}/{β×(γ×V´)/(ω×C)}
=C
The control arithmetic circuit 16 performs a correction operation using AD (FB) / AD (MEAS) as a measurement result RESULT.
RESULT = AD (FB) / AD (MEAS)
= {Β × (γ × V ′) / ω} / {β × (γ × V ′) / (ω × C)}
= C

以上のように構成することにより、計測結果RESULTからは正弦波発生回路12の係数γおよび電流振幅検出回路15の係数βが消去され、温度等によりこれらの回路の特性が変動しても影響を受けないことになる。また、これにより、電流検出回路15や正弦波発生回路12を高精度化しなくても、高精度の測定を行うことができるという利点がある。   With the above configuration, the coefficient γ of the sine wave generation circuit 12 and the coefficient β of the current amplitude detection circuit 15 are deleted from the measurement result RESULT, and even if the characteristics of these circuits fluctuate due to temperature or the like, there is an effect. You will not receive it. This also has the advantage that high-precision measurement can be performed without increasing the accuracy of the current detection circuit 15 and the sine wave generation circuit 12.

図3は本発明による計測装置の他の実施例を示すブロック図であり、温度を測定する計測装置に適用した一例を示したものである。   FIG. 3 is a block diagram showing another embodiment of the measuring apparatus according to the present invention, and shows an example applied to a measuring apparatus for measuring temperature.

温度センサ21は測定対象の温度を抵抗値として出力する。定電流発生回路23は定電流を生成し、温度センサ21に駆動信号S21として供給する。なお、温度センサ21が電流変動によって受ける影響が少ない場合には定電圧発生回路とすることも可能である。   The temperature sensor 21 outputs the temperature to be measured as a resistance value. The constant current generation circuit 23 generates a constant current and supplies it to the temperature sensor 21 as a drive signal S21. If the temperature sensor 21 is less affected by current fluctuation, a constant voltage generation circuit can be used.

定電流発生回路23にて生成した電流(駆動信号S21)は、温度センサ21と、温度センサ21に直列に接続された電流検出抵抗22に流れ、それぞれ抵抗値の大きさに応じた電圧降下を生じさせる。温度センサ21によって生じた電圧降下は温度センサ測定信号S22として信号切替部24に入力される。また、電流検出抵抗22によって生じた電圧降下は電流検出信号S23として信号切替部24に入力される。   The current (driving signal S21) generated by the constant current generation circuit 23 flows to the temperature sensor 21 and the current detection resistor 22 connected in series to the temperature sensor 21, and a voltage drop corresponding to the magnitude of the respective resistance values. Cause it to occur. The voltage drop generated by the temperature sensor 21 is input to the signal switching unit 24 as a temperature sensor measurement signal S22. The voltage drop generated by the current detection resistor 22 is input to the signal switching unit 24 as a current detection signal S23.

温度センサ測定信号S22と電流検出信号S23は、信号切替部24で選択的に切り替えられて差動電圧検出回路25に取り込まれる。差動電圧検出回路25は信号切替部24から入力される差動信号の信号レベルに対応するA/D値を求め、制御演算回路26に出力する。ここで、図3に示すように、定電流発生回路23の出力段の電位をV1、温度センサ21と電流検出抵抗23の接続部の電位をV2、電流検出抵抗23の電流出力段の電位をV3とする。   The temperature sensor measurement signal S22 and the current detection signal S23 are selectively switched by the signal switching unit 24 and taken into the differential voltage detection circuit 25. The differential voltage detection circuit 25 calculates an A / D value corresponding to the signal level of the differential signal input from the signal switching unit 24 and outputs the A / D value to the control arithmetic circuit 26. Here, as shown in FIG. 3, the potential of the output stage of the constant current generation circuit 23 is V1, the potential of the connection part of the temperature sensor 21 and the current detection resistor 23 is V2, and the potential of the current output stage of the current detection resistor 23 is V3.

制御演算回路26は補正演算部261と、切替信号S24を用いて信号切替部24を制御する切替制御部262を有し、差動電圧検出回路25において温度センサ測定信号S22と電流検出信号S23のどちらの信号の信号レベルを検出するかを決定する。たとえば、まず温度センサ測定信号S22を差動電圧検出回路25に出力してA/D値を求め、その後差動電圧検出回路25への入力を電流検出信号S23に切り替えてそのA/D値を求める。得られた温度センサ測定信号S22と電流検出信号S23のA/D値をもとに補正演算処理および表示データ生成処理を行い、結果を表示回路27に出力する。また、切替制御部262の有する切替情報は、補正演算部261において信号切替と同期した信号の取り込みを行うために利用される。   The control calculation circuit 26 includes a correction calculation unit 261 and a switching control unit 262 that controls the signal switching unit 24 using the switching signal S24. In the differential voltage detection circuit 25, the temperature sensor measurement signal S22 and the current detection signal S23 are controlled. Decide which signal level to detect. For example, first, the temperature sensor measurement signal S22 is output to the differential voltage detection circuit 25 to obtain an A / D value, and then the input to the differential voltage detection circuit 25 is switched to the current detection signal S23 to change the A / D value. Ask. Based on the obtained A / D values of the temperature sensor measurement signal S22 and the current detection signal S23, correction calculation processing and display data generation processing are performed, and the result is output to the display circuit 27. In addition, the switching information included in the switching control unit 262 is used by the correction calculation unit 261 to capture a signal synchronized with the signal switching.

測定原理は以下の通りとなる。定電流発生回路23から出力される駆動信号S21の電流をI、温度センサ21の抵抗値をR(MEAS)、電流検出抵抗22の抵抗値をR(REF)とし、温度センサ21の両端の電位差(=V1−V2)をV(MEAS)、電流検出抵抗22の両端の電位差(=V2−V3)をV(REF)とすると、
V(MEAS)=R(MEAS)×I
V(REF)=R(REF)×I
となる。
The measurement principle is as follows. The current of the drive signal S21 output from the constant current generation circuit 23 is I, the resistance value of the temperature sensor 21 is R (MEAS), the resistance value of the current detection resistor 22 is R (REF), and the potential difference between both ends of the temperature sensor 21 When (= V1-V2) is V (MEAS) and the potential difference between both ends of the current detection resistor 22 (= V2-V3) is V (REF),
V (MEAS) = R (MEAS) × I
V (REF) = R (REF) × I
It becomes.

ここで、駆動信号S21の電流Iには、定電流発生回路23自体の係数が含まれるため、以下のように表すことができる。
I=γ×I´
I´は定電流発生回路23の真の出力電流、γは定電流発生回路23の係数である。
Here, since the current I of the drive signal S21 includes the coefficient of the constant current generation circuit 23 itself, it can be expressed as follows.
I = γ × I ′
I ′ is a true output current of the constant current generating circuit 23, and γ is a coefficient of the constant current generating circuit 23.

差動電圧検出回路25のA/D値出力は以下の式で示すことができる。
AD(MEAS)=β×V(MEAS)=β×R(MEAS)×(γ×I´)
AD(REF)=β×V(REF)=β×R(REF)×(γ×I´)
REFはフィードバック信号である電流検出信号S23、MEASは温度センサ測定信号S22、βは差動電圧検出回路25の変換係数である。
The A / D value output of the differential voltage detection circuit 25 can be expressed by the following equation.
AD (MEAS) = β × V (MEAS) = β × R (MEAS) × (γ × I ′)
AD (REF) = β × V (REF) = β × R (REF) × (γ × I ′)
REF is a current detection signal S23 that is a feedback signal, MEAS is a temperature sensor measurement signal S22, and β is a conversion coefficient of the differential voltage detection circuit 25.

制御演算回路26ではAD(MEAS)/AD(REF)を計測結果RESULTとする補正演算を行う。
RESULT=AD(MEAS)/AD(REF)
=(β/β)×(γ/γ)×(I´/I´)×(R(MEAS)/R(REF))
=R(MEAS)/R(REF)
The control arithmetic circuit 26 performs a correction calculation using AD (MEAS) / AD (REF) as a measurement result RESULT.
RESULT = AD (MEAS) / AD (REF)
= (Β / β) × (γ / γ) × (I ′ / I ′) × (R (MEAS) / R (REF))
= R (MEAS) / R (REF)

以上より、計測結果RESULTからは定電流発生回路23や差動電圧検出回路25の係数γ、βが消去され、温度等によりこれらの回路の特性が変動しても影響を受けないことになる。また、これにより、差動電圧検出回路25や定電流発生回路23を高精度化しなくても、高精度の測定を行うことができるという利点がある。   As described above, the coefficients γ and β of the constant current generation circuit 23 and the differential voltage detection circuit 25 are deleted from the measurement result RESULT, and even if the characteristics of these circuits fluctuate due to temperature or the like, they are not affected. This also has the advantage that high-precision measurement can be performed without increasing the accuracy of the differential voltage detection circuit 25 and the constant current generation circuit 23.

図1は本発明による計測装置の一実施例を示すブロック図。FIG. 1 is a block diagram showing an embodiment of a measuring apparatus according to the present invention. 図2は本発明による計測装置の他の実施例を示すブロック図。FIG. 2 is a block diagram showing another embodiment of the measuring apparatus according to the present invention. 図3は本発明による計測装置の他の実施例を示すブロック図。FIG. 3 is a block diagram showing another embodiment of the measuring apparatus according to the present invention. 図4は従来の計測装置の一例を示したブロック図。FIG. 4 is a block diagram showing an example of a conventional measuring apparatus. 図5は図4(b)の回路例において信号検出部105および106のゲインが計測結果に与える影響の説明図。FIG. 5 is an explanatory diagram of the influence of the gains of the signal detection units 105 and 106 on the measurement result in the circuit example of FIG.

符号の説明Explanation of symbols

1 センサ
2 駆動信号生成部
3 信号切替部
4 信号検出部
5 補正演算部
DESCRIPTION OF SYMBOLS 1 Sensor 2 Drive signal generation part 3 Signal switching part 4 Signal detection part 5 Correction calculation part

Claims (7)

センサに駆動信号を供給するとともに測定対象の物理量変化に対応したセンサ出力信号を検出する計測方法において、
前記駆動信号および前記センサ出力信号を選択的に切り替える切替ステップと、
前記切替ステップにより選択された前記センサ出力信号の信号レベルを検出する第1の演算ステップと、
前記切替ステップにより選択された前記駆動信号の信号レベルを検出する第2の演算ステップと、
前記第1および第2の演算ステップの出力を利用して補正された測定出力信号を得る補正演算ステップと、
を有することを特徴とする計測方法。
In a measurement method for supplying a drive signal to a sensor and detecting a sensor output signal corresponding to a physical quantity change of a measurement target,
A switching step of selectively switching the drive signal and the sensor output signal;
A first calculation step of detecting a signal level of the sensor output signal selected by the switching step;
A second calculation step of detecting a signal level of the drive signal selected by the switching step;
A correction calculation step for obtaining a corrected measurement output signal using the outputs of the first and second calculation steps;
A measurement method characterized by comprising:
前記補正演算ステップは、前記第1の演算ステップの出力を前記第2の演算ステップの出力で除算することを特徴とする請求項1に記載の計測方法。   The measurement method according to claim 1, wherein the correction calculation step divides the output of the first calculation step by the output of the second calculation step. 前記第1および第2の演算ステップは、切替ステップに同期して選択的に実施されることを特徴とする請求項1または2に記載の計測方法。   The measurement method according to claim 1, wherein the first and second calculation steps are selectively performed in synchronization with the switching step. センサに駆動信号を供給するとともに測定対象の物理量変化に対応したセンサ出力信号を検出する計測装置において、
前記駆動信号および前記センサ出力信号が入力され、いずれか一方の信号を選択的に切り替えて出力する信号切替部と、
この信号切替部から出力される信号の信号レベルを検出する信号検出部と、
前記信号検出部から出力された前記駆動信号およびセンサ出力信号の演算結果を利用して補正された測定出力信号を発生する補正演算部と、
を有することを特徴とする計測装置。
In a measuring device that supplies a drive signal to a sensor and detects a sensor output signal corresponding to a physical quantity change of a measurement target,
The drive signal and the sensor output signal are input, and a signal switching unit that selectively switches and outputs one of the signals;
A signal detection unit for detecting the signal level of the signal output from the signal switching unit;
A correction calculation unit that generates a measurement output signal corrected using the calculation result of the drive signal and sensor output signal output from the signal detection unit;
A measuring apparatus comprising:
前記補正演算部は、前記センサ出力信号に応じた演算出力を前記駆動信号に応じた演算出力で除算して補正演算を行うことを特徴とする請求項4に記載の計測装置。   The measurement apparatus according to claim 4, wherein the correction calculation unit performs a correction calculation by dividing a calculation output corresponding to the sensor output signal by a calculation output corresponding to the drive signal. 前記補正演算部は、前記信号切替部の切替動作に同期して前記駆動信号および前記センサ出力信号の演算結果を取り込むことを特徴とする請求項4または5に記載の計測装置。   The measurement apparatus according to claim 4, wherein the correction calculation unit captures calculation results of the drive signal and the sensor output signal in synchronization with a switching operation of the signal switching unit. 前記センサは駆動電圧の供給を受けて燃料タンク内の液面レベルに応じた電流信号を出力する静電容量式のタンクユニットであり、
前記駆動電圧を電流信号に変換して前記信号切替部に出力するレベル変換回路を有し、
前記信号検出部は前記タンクユニットから出力される電流信号または前記レベル変換回路から出力される電流信号の信号レベルを検出する電流振幅検出回路であることを特徴とする請求項4乃至6のいずれかに記載の計測装置。
The sensor is a capacitive tank unit that receives a supply of drive voltage and outputs a current signal corresponding to a liquid level in the fuel tank,
A level conversion circuit that converts the drive voltage into a current signal and outputs the current signal to the signal switching unit;
7. The signal amplitude detection circuit according to claim 4, wherein the signal detection unit is a current amplitude detection circuit that detects a signal level of a current signal output from the tank unit or a current signal output from the level conversion circuit. The measuring device described in 1.
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JP2011174718A (en) * 2010-02-23 2011-09-08 Seiko Epson Corp Interface measurement sensor, interface measurement device, interface measurement system, and interface measurement method
JP2012037238A (en) * 2010-08-03 2012-02-23 Kobe Steel Ltd Monitoring device for sensor
JP2016510889A (en) * 2013-03-11 2016-04-11 ローズマウント インコーポレイテッド Digital correction process transmitter with reduced dead time

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JPH11101680A (en) * 1997-09-29 1999-04-13 Tohoku Ricoh Co Ltd Ink quantity detecting circuit for printing machine
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Publication number Priority date Publication date Assignee Title
JP2011174718A (en) * 2010-02-23 2011-09-08 Seiko Epson Corp Interface measurement sensor, interface measurement device, interface measurement system, and interface measurement method
JP2012037238A (en) * 2010-08-03 2012-02-23 Kobe Steel Ltd Monitoring device for sensor
JP2016510889A (en) * 2013-03-11 2016-04-11 ローズマウント インコーポレイテッド Digital correction process transmitter with reduced dead time

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