JP2012073937A

JP2012073937A - Two-wire transmitter, compensation circuit

Info

Publication number: JP2012073937A
Application number: JP2010219748A
Authority: JP
Inventors: Tomoatsu Tanahashi; 友厚棚橋
Original assignee: Asahi Kasei Electronics Co Ltd
Current assignee: Asahi Kasei Electronics Co Ltd
Priority date: 2010-09-29
Filing date: 2010-09-29
Publication date: 2012-04-12

Abstract

PROBLEM TO BE SOLVED: To provide a two-wire transmitter by which the degree of precision of an analog voltage signal received by a receiver of a latter stage is not lowered even if the receiver of the latter stage receiving the signal from a two-wire transmission line has a ratiometric characteristic.SOLUTION: A two-wire transmitter which converts a sensor signal to an analog voltage signal and outputs the analog voltage signal to a transmission line includes: resistance elements 103, 104 generating a midpoint potential signal relative to a midpoint potential between a transmission line 1 and a reference transmission line 2; an operational amplifier 102 to which the sensor signal and the midpoint potential signal are delivered; a computing unit 111 generating the analog voltage signal on the basis of a signal outputted by the operational amplifier 102; a current source 106 correcting the sensor signal such that the sensor signal has a ratiometric characteristic; an analog voltage signal voltage divider 107; a measuring apparatus 108; a voltage generator 109; and a computing unit 110.

Description

本発明は、２線式伝送器、補正回路にかかり、特にセンサによって検出されたセンサ信号を、レシオメトリック特性を有するアナログ電圧信号として出力する２線式伝送器、補正回路に関する。 The present invention relates to a two-wire transmitter and a correction circuit, and more particularly to a two-wire transmitter and a correction circuit that output a sensor signal detected by a sensor as an analog voltage signal having a ratiometric characteristic.

２線式伝送器は、流量や圧力といった物理量を検出し、検出値（以降、センサ信号と記す）を出力する機器である。センサ信号をアナログ電圧信号に変換して出力する２線式伝送器としては、例えば、特許文献１に記載されたものが挙げられる。
図６は、特許文献１に記された２線式伝送器の従来技術を説明するための図である。図示した２線式伝送器６１０は、センサＳによって出力されるセンサ信号Ｍ1、Ｍ2を増幅するオペアンプ６１と、オペアンプ６１から出力されたセンサ信号Ｖsnsの電圧値に応じて接続先が切り替えられるスイッチ６３と、スイッチ６３に接続された抵抗素子６５、６６、６７を備えている。また、２線式伝送器６１０は、基準電圧発生部６４と、スイッチ６３に接続される抵抗素子６６、抵抗素子６７の大きさによって出力電流Ｉoutが変化するオペアンプ６２を備えている。センサＳは、例えば、磁気、温度、圧力といった物理量を検出するセンサである。 The two-wire transmitter is a device that detects a physical quantity such as a flow rate or pressure and outputs a detection value (hereinafter referred to as a sensor signal). An example of a two-wire transmitter that converts a sensor signal into an analog voltage signal and outputs the analog voltage signal is described in Patent Document 1.
FIG. 6 is a diagram for explaining the prior art of the two-wire transmitter described in Patent Document 1. In FIG. The illustrated two-wire transmitter 610 includes an operational amplifier 61 that amplifies the sensor signals M1 and M2 output from the sensor S, and a switch 63 whose connection destination is switched according to the voltage value of the sensor signal Vsns output from the operational amplifier 61. And resistive elements 65, 66 and 67 connected to the switch 63. The two-wire transmitter 610 includes a reference voltage generator 64, a resistance element 66 connected to the switch 63, and an operational amplifier 62 whose output current Iout varies depending on the size of the resistance element 67. The sensor S is a sensor that detects physical quantities such as magnetism, temperature, and pressure.

図６に示した２線式伝送器６１０は、以下のように動作する。
オペアンプ６１は、連続的に変化するセンサ信号Ｖsnsを出力する。センサ信号Ｖsnsが所定の閾値を超えると、スイッチ６３の接続先が抵抗素子６６から抵抗素子６７に切り替わる。オペアンプ６２の出力信号Ｖoutとグラウンド（ＧＮＤ）の電位差は、抵抗素子６５、スイッチ６３に接続されている抵抗素子６６または抵抗素子６７によって分圧される。分圧された電位に応じた信号は、フィードバック信号Ｖfbとしてオペアンプ６２に入力される。オペアンプ６２は、基準電圧発生部６４によって生成されると基準電圧Ｖrefとフィードバック信号Ｖfbの電圧値を等しくするように動作する。 The two-wire transmitter 610 shown in FIG. 6 operates as follows.
The operational amplifier 61 outputs a continuously changing sensor signal Vsns. When the sensor signal Vsns exceeds a predetermined threshold value, the connection destination of the switch 63 is switched from the resistance element 66 to the resistance element 67. The potential difference between the output signal Vout of the operational amplifier 62 and the ground (GND) is divided by the resistive element 65 and the resistive element 66 or the resistive element 67 connected to the switch 63. A signal corresponding to the divided potential is input to the operational amplifier 62 as a feedback signal Vfb. When the operational amplifier 62 is generated by the reference voltage generator 64, the operational amplifier 62 operates so that the voltage values of the reference voltage Vref and the feedback signal Vfb are equal.

このため、オペアンプ６２は、フィードバック信号Ｖfbの電圧値が上昇すると、出力電流Ｉoutを増加させるように動作する。このとき、出力信号Ｖoutは、基準電圧Ｖrefとフィードバック信号Ｖfbの電圧値とが等しくなるように低下する。
一方、フィードバック信号Ｖfbが低下すると、オペアンプ６２は出力電流Ｉoutを減少させるように動作する。この結果、オペアンプ６２の出力信号Ｖoutは、基準電圧Ｖrefとフィードバック信号Ｖfbとが等しくなるように上昇する。
本願発明の発明者らは、上記した特許文献１の、センサ信号Ｖsnsが連続的に変化するにも関わらず、出力信号Ｖoutが離散的に変化することに鑑みて、センサ信号Ｖsnsの変化に伴って出力信号Ｖoutが連続的に変化するアナログ電圧信号を出力する２線式伝送器を発明した。 Therefore, the operational amplifier 62 operates so as to increase the output current Iout when the voltage value of the feedback signal Vfb increases. At this time, the output signal Vout decreases so that the reference voltage Vref and the voltage value of the feedback signal Vfb become equal.
On the other hand, when the feedback signal Vfb decreases, the operational amplifier 62 operates to decrease the output current Iout. As a result, the output signal Vout of the operational amplifier 62 rises so that the reference voltage Vref and the feedback signal Vfb are equal.
The inventors of the present invention consider that the output signal Vout changes discretely in spite of the fact that the sensor signal Vsns continuously changes in Patent Document 1 described above, and that the sensor signal Vsns changes. Invented a two-wire transmitter that outputs an analog voltage signal whose output signal Vout continuously changes.

図７は、本願発明の発明者らが発明した２線式伝送器を説明するための図である。図示した２線式伝送器は、温度センサ、磁気センサ、圧力センサ等のセンサＳと、センサＳの出力信号Ｖsnsを増幅するオペアンプ７１と、オペアンプ７１の出力信号によって出力電流Ｉoutが変化する第1の電流源７２と、第1の抵抗素子７３（抵抗値Ｒ0）及び第２の抵抗素子７４（抵抗値Ｒ1）によって構成されている。なお、第２の電流源７５からは、アナログ電圧信号Ｖoutが出力される伝送路１からグラウンドＧＮＤに流れる電流のうち、第1の電流源７２に流れる電流以外のすべての電流の総和が流れている。
図７に示した受信機７７は、２つの伝送路から信号を受けるＣＰＵ等の受信機７７を備えていて、受信機７７は、伝送路の一方から抵抗素子７６を介して電源から電源電圧Ｖccの供給を受けている。 FIG. 7 is a diagram for explaining a two-wire transmitter invented by the inventors of the present invention. The illustrated two-wire transmitter includes a sensor S such as a temperature sensor, a magnetic sensor, and a pressure sensor, an operational amplifier 71 that amplifies the output signal Vsns of the sensor S, and a first output current Iout that varies depending on the output signal of the operational amplifier 71. Current source 72, a first resistance element 73 (resistance value R0), and a second resistance element 74 (resistance value R1). From the second current source 75, the sum of all currents flowing from the transmission line 1 from which the analog voltage signal Vout is output to the ground GND, except for the current flowing to the first current source 72, flows. Yes.
The receiver 77 shown in FIG. 7 includes a receiver 77 such as a CPU that receives signals from two transmission paths. The receiver 77 is connected to a power supply voltage Vcc from a power source via a resistance element 76 from one of the transmission paths. Is receiving the supply.

次に、このように構成された２線式伝送器の動作について説明する。アナログ電圧信号ＶoutとグラウンドＧＮＤの電位差を第1の抵抗素子７３及び第２の抵抗素子７４によって分圧した電圧をフィードバック電圧Ｖfbとするとき、オペアンプ７１はセンサ信号Ｖsnsとフィードバック信号Ｖfbの電圧が等しくなるように動作する。具体的には、センサ信号Ｖsnsが上昇するとオペアンプＯＰは出力電流Ｉoutを減少させるように動作し、センサ信号Ｖsnsとフィードバック信号Ｖfbが等しくなるようにアナログ電圧信号Ｖoutが上昇する。センサ信号Ｖsnsが低下するとオペアンプＯＰは出力電流Ｉoutを増加させるように動作し、センサ信号Ｖsnsとフィードバック信号Ｖfbが等しくなるようにアナログ電圧信号Ｖoutが低下する。 Next, the operation of the two-wire transmitter configured as described above will be described. When the voltage obtained by dividing the potential difference between the analog voltage signal Vout and the ground GND by the first resistance element 73 and the second resistance element 74 is used as the feedback voltage Vfb, the operational amplifier 71 has the same voltage between the sensor signal Vsns and the feedback signal Vfb. It works to be. Specifically, when the sensor signal Vsns rises, the operational amplifier OP operates to decrease the output current Iout, and the analog voltage signal Vout rises so that the sensor signal Vsns and the feedback signal Vfb become equal. When the sensor signal Vsns decreases, the operational amplifier OP operates to increase the output current Iout, and the analog voltage signal Vout decreases so that the sensor signal Vsns and the feedback signal Vfb become equal.

したがって、センサ信号Ｖsnsが連続的に変化するとき、アナログ電圧信号Ｖoutも連続的に変化する。すなわち、センサ信号Ｖsnsが連続的なアナログ電圧信号に変換される。この２線式伝送器のセンサ信号Ｖsnsとアナログ電圧信号Ｖoutの関係は、次の式（１）で表される。
Ｖout＝（１＋（Ｒ0／Ｒ1））・Ｖsns …式（１） Therefore, when the sensor signal Vsns changes continuously, the analog voltage signal Vout also changes continuously. That is, the sensor signal Vsns is converted into a continuous analog voltage signal. The relationship between the sensor signal Vsns and the analog voltage signal Vout of this two-wire transmitter is expressed by the following equation (1).
Vout = (1+ (R0 / R1)). Vsns (1)

ところで、センサ信号をアナログ電圧信号に変換して出力する伝送器には、出力信号がレシオメトリック特性を有するアナログ電圧信号のもの（以下、本明細書ではレシオメトリック型の２線伝送器と記す）と、出力信号が非レシオメトリック特性を有するアナログ電圧信号のもの（以下、本明細書では非レシオメトリック型の２線伝送器と記す）がある。ここで、レシオメトリック特性とは、センサに与えられる電源電圧の変動に比例して信号の電圧レベルが変動する特性であり、非レシオメトリック特性とは、信号の電圧レベルが電源電圧の変動に比例しない特性である。図７に示した本願発明の発明者らが発明した２線式伝送器は、非レシオメトリック型の２線式伝送器である。 By the way, a transmitter that converts a sensor signal into an analog voltage signal and outputs the analog voltage signal has a ratiometric characteristic (hereinafter referred to as a ratiometric type two-wire transmitter in this specification). And an analog voltage signal whose output signal has non-ratiometric characteristics (hereinafter referred to as a non-ratiometric type two-wire transmitter). Here, the ratiometric characteristic is a characteristic that the signal voltage level fluctuates in proportion to the fluctuation of the power supply voltage applied to the sensor, and the non-ratiometric characteristic is the signal voltage level that is proportional to the fluctuation of the power supply voltage. It is a characteristic that does not. The two-wire transmitter invented by the inventors of the present invention shown in FIG. 7 is a non-ratiometric two-wire transmitter.

非レシオメトリック型の２線式伝送器では、２線式伝送器の２つの伝送路から信号を受ける後段の受信機７７も非レシオメトリック特性を有するものを用いることが望ましい。この理由は、電源電圧Ｖccが変動すると受信機側の入力特性は変動するが、アナログ電圧信号は変動しないため、受信機が受けるアナログ電圧信号の精度が低下するという問題が発生するためである。 In the non-ratiometric type two-wire transmitter, it is desirable to use a receiver 77 having a non-ratiometric characteristic as a subsequent receiver 77 that receives signals from two transmission lines of the two-wire transmitter. This is because when the power supply voltage Vcc fluctuates, the input characteristics on the receiver side fluctuate, but the analog voltage signal does not fluctuate, causing a problem that the accuracy of the analog voltage signal received by the receiver decreases.

非レシオメトリック型の２線式伝送器にレシオメトリック特性を有する受信機７７を用いる場合、２線伝送器の非レシオメトリック特性を有する信号を補正してレシオメトリック特性を有する信号を出力するレシオメトリック補正回路がある。レシオメトリック補正回路の従来技術としては、例えば、特許文献２に記載のレシオメトリック補正回路が上げられる。図８は、特許文献２に記載されているレシオメトリック補正回路を含む回路のブロック図である。このようなレシオメトリック補正回路８１は、センサ素子８２に直接印加された電源電圧ＶDDの変動を検出して補正量を算出している。 When a receiver 77 having a ratiometric characteristic is used for a non-ratiometric type two-wire transmitter, a ratiometric that corrects a signal having a non-ratiometric characteristic of the two-wire transmitter and outputs a signal having a ratiometric characteristic There is a correction circuit. As a prior art of the ratiometric correction circuit, for example, a ratiometric correction circuit described in Patent Document 2 can be cited. FIG. 8 is a block diagram of a circuit including the ratiometric correction circuit described in Patent Document 2. In FIG. Such a ratiometric correction circuit 81 detects a change in the power supply voltage VDD directly applied to the sensor element 82 and calculates a correction amount.

ＵＳ６４３７５８１Ｂ１US 6437581 B1 特開２０１０−８５３１９号公報JP 2010-85319 A

しかしながら、図７に記載の非レシオメトリック型の２線伝送器では、抵抗素子７６を介して電源電圧Ｖccが受信機７７に供給される構成であるからレシオメトリック補正回路を使って電源電圧Ｖccの変動を直接検出することができない。また、前記したように、図７に記載の２線式伝送器は、非レシオメトリック型の２線伝送器であることから、電源電圧Ｖccが変動しても出力信号Ｖoutは変動せず、レシオメトリック補正回路が電源電圧Ｖccの変動を検出することができない。 However, in the non-ratiometric type two-wire transmitter shown in FIG. 7, the power supply voltage Vcc is supplied to the receiver 77 via the resistance element 76. Variations cannot be detected directly. Further, as described above, since the two-wire transmitter shown in FIG. 7 is a non-ratiometric type two-wire transmitter, the output signal Vout does not fluctuate even if the power supply voltage Vcc fluctuates. The metric correction circuit cannot detect the fluctuation of the power supply voltage Vcc.

このため、図７に記載の２線式伝送器では、レシオメトリック補正回路を使って信号を補正することができず、レシオメトリック型の受信機を適用することができなくなる。
本発明は、このような点に鑑みてなされたものであって、レシオメトリック特性を有する信号を出力することによって、２線の伝送路から信号を受ける後段の受信機（例えばＣＰＵ等）がレシオメトリック特性を有する場合でも、受信機が受けるアナログ電圧信号の精度が低下しない、２線式伝送器、補正回路を提供することを目的とする。 For this reason, the two-wire transmitter shown in FIG. 7 cannot correct the signal using the ratiometric correction circuit and cannot apply the ratiometric receiver.
The present invention has been made in view of the above points, and by outputting a signal having a ratiometric characteristic, a subsequent receiver (for example, a CPU or the like) that receives a signal from a two-wire transmission line has a ratio. An object of the present invention is to provide a two-wire transmitter and a correction circuit in which the accuracy of an analog voltage signal received by a receiver does not deteriorate even when it has metric characteristics.

上記した課題を解決するため、本発明の２線式伝送器は、センサ信号をアナログ電圧信号に変換して伝送路に出力する２線式伝送器であって、前記伝送路（例えば図１に示した伝送路１）と基準伝送路（例えば図１に示した基準伝送路２）との間の中間電位に関する中間電位信号を生成する中間電位信号生成手段（例えば図１に示した抵抗素子１０３、１０４）と、前記センサ信号と前記中間電位信号とが供給される増幅器（例えば図１に示したオペアンプ１０２）と、前記増幅器によって出力される信号に基づいて、前記アナログ電圧信号を生成するアナログ電圧信号生成手段（例えば図１に示した演算器１１１）と、前記センサ信号がセンサに与えられる電源電圧の変動に比例して信号の電圧レベルが変動する特性であるレシオメトリック特性を持つように、前記センサ信号を補正するレシオメトリック特性補正手段（例えば図１に示した電流源１０６、アナログ電圧信号分圧器１０７、測定器１０８、電圧生成器１０９、演算器１１０）と、を含むことを特徴とする。 In order to solve the above-described problems, a two-wire transmitter of the present invention is a two-wire transmitter that converts a sensor signal into an analog voltage signal and outputs the analog voltage signal to the transmission line. Intermediate potential signal generating means (for example, the resistance element 103 shown in FIG. 1) for generating an intermediate potential signal relating to the intermediate potential between the indicated transmission line 1) and a reference transmission line (eg, the reference transmission line 2 shown in FIG. 1). 104), an amplifier (for example, the operational amplifier 102 shown in FIG. 1) to which the sensor signal and the intermediate potential signal are supplied, and an analog that generates the analog voltage signal based on the signal output by the amplifier Voltage signal generating means (for example, the arithmetic unit 111 shown in FIG. 1), and ratiometric, which is a characteristic that the voltage level of the signal fluctuates in proportion to the fluctuation of the power supply voltage applied to the sensor. Ratiometric characteristic correction means (for example, the current source 106, the analog voltage signal voltage divider 107, the measuring instrument 108, the voltage generator 109, and the arithmetic unit 110 shown in FIG. 1) for correcting the sensor signal so as to have characteristics. It is characterized by including.

また、本発明の２線式伝送器は、上記した発明において、前記レシオメトリック特性補正手段が、前記センサ信号がセンサに与えられる電源電圧の変動に比例して信号の電圧レベルが変動する特性であるレシオメトリック特性を持つように、前記アナログ電圧信号の補正演算を行う補正演算手段と、前記補正演算手段による補正に使用される補正量を算出する補正量算出手段と、を含むことを特徴とする。
また、本発明の２線式伝送器は、上記した発明において、前記補正量算出手段が、前記センサ信号をアナログ電圧信号に変換して伝送路に出力する２線式伝送器としての動作が行われていないとき、前記補正演算手段による補正に使用される補正量を算出することを特徴とする。 In the two-wire transmitter according to the present invention, the ratiometric characteristic correcting means may have a characteristic that the voltage level of the signal varies in proportion to the variation of the power supply voltage applied to the sensor. Correction correction means for performing correction calculation of the analog voltage signal so as to have a certain ratiometric characteristic, and correction amount calculation means for calculating a correction amount used for correction by the correction calculation means, To do.
In the two-wire transmitter of the present invention, the correction amount calculating means operates as a two-wire transmitter that converts the sensor signal into an analog voltage signal and outputs the analog voltage signal to the transmission line. If not, the correction amount used for correction by the correction calculation means is calculated.

また、本発明の２線式伝送器は、上記した発明において、前記レシオメトリック特性補正手段が、バイアス電流生成手段（例えば図１に示した電流源１０６）と、前記アナログ電圧信号を分圧する手段（例えば図１に示したアナログ電圧信号分圧器１０７）と、前記アナログ電圧信号の分圧を検出し、前記バイアス電流と前記アナログ電圧信号の分圧に基づいて電源電圧の分圧を算出する算出手段（例えば図１に示した測定器１０８）と、理想的な電源電圧の分圧に相当する電圧を生成する手段（例えば図１に示した電圧生成器１０９）と、前記電源電圧の分圧の算出値と理想的な電源電圧の分圧に相当する電圧に応じて前記アナログ電圧信号の補正量を算出する演算手段と、前記補正量に基づき前記アナログ電圧信号の補正演算を行う演算手段（例えば図１に示した演算器１１０）と、を含むことが望ましい。 In the two-wire transmitter according to the present invention, in the above-described invention, the ratiometric characteristic correcting unit may be a bias current generating unit (for example, the current source 106 shown in FIG. 1) and a unit that divides the analog voltage signal. (For example, the analog voltage signal voltage divider 107 shown in FIG. 1) and a calculation for detecting the divided voltage of the analog voltage signal and calculating the divided voltage of the power supply voltage based on the bias current and the divided voltage of the analog voltage signal. Means (for example, the measuring device 108 shown in FIG. 1), means for generating a voltage corresponding to an ideal divided voltage of the power supply voltage (for example, the voltage generator 109 shown in FIG. 1), and the divided voltage of the power supply voltage Calculating means for calculating the correction amount of the analog voltage signal in accordance with the calculated value and a voltage corresponding to an ideal voltage division of the power supply voltage, and an operation for correcting the analog voltage signal based on the correction amount Stage (e.g., calculator 110 shown in FIG. 1), it is desirable to include.

また、本発明の２線式伝送器は、上記した発明において、前記レシオメトリック特性補正手段は、第１の電流を流して測定された第１の検出電圧と、第２の電流を流して測定された第２の検出電圧と、に基づき、電源電圧の分圧を算出することが望ましい。
また、本発明の２線式伝送器は、上記した発明において、前記レシオメトリック特性補正手段は、前記算出された電源電圧の分圧と理想的な電源電圧の分圧に相当する電圧に応じてアナログ電圧信号の補正量を算出することが望ましい。 In the two-wire transmitter according to the present invention, the ratiometric characteristic correcting unit may measure the first detection voltage measured by flowing the first current and the second current. It is desirable to calculate the divided voltage of the power supply voltage based on the second detected voltage.
In the two-wire transmitter according to the present invention, the ratiometric characteristic correcting unit may be configured so that the ratiometric characteristic correcting unit corresponds to a voltage corresponding to the divided power supply voltage and an ideal divided power supply voltage. It is desirable to calculate the correction amount of the analog voltage signal.

また、本発明の２線式伝送器は、上記した発明において、前記レシオメトリック特性補正手段が、前記補正量と前記センサ信号を乗算することが望ましい。
また、本発明の２線式伝送器は、上記した発明において、前記増幅器が、前記センサ信号と前記中間電位信号とが供給され、入力された前記センサ信号と前記中間電位信号とが等しくなるように、前記伝送路と前記基準伝送路との間の電位を制御する信号を出力することを特徴とする。 In the two-wire transmitter of the present invention, in the above-described invention, it is preferable that the ratiometric characteristic correcting unit multiplies the correction amount by the sensor signal.
In the two-wire transmitter according to the present invention, the amplifier is supplied with the sensor signal and the intermediate potential signal so that the input sensor signal and the intermediate potential signal are equal. In addition, a signal for controlling a potential between the transmission line and the reference transmission line is output.

また、本発明の２線式伝送器は、上記した発明において、前記センサ信号がアナログ信号である場合、前記センサ信号をデジタル信号に変換する第１の変換回路（例えば図５に示したアナログ・デジタル変換器５０１）と、前記アナログ電圧信号の分圧をデジタル信号に変換する第２の変換回路（例えば図５に示したアナログ・デジタル変換器５０２）と、前記第１及び第２の変換回路によって変換されたデジタル信号に基づいてレシオメトリック特性に補正されたデジタル信号を出力する加工回路（例えば図５に示したデジタル演算回路５００）と、前記加工回路によって補正されたデジタル信号をアナログ信号に変換して前記増幅器に出力するデジタル・アナログ変換回路（例えば図５に示したデジタル・アナログ変換器５０３）と、をさらに含むことが望ましい。 Further, the two-wire transmitter according to the present invention provides a first conversion circuit that converts the sensor signal into a digital signal when the sensor signal is an analog signal (for example, the analog signal shown in FIG. 5). A digital converter 501), a second conversion circuit (for example, the analog-digital converter 502 shown in FIG. 5) for converting the divided voltage of the analog voltage signal into a digital signal, and the first and second conversion circuits. A processing circuit (for example, the digital arithmetic circuit 500 shown in FIG. 5) that outputs a digital signal that has been corrected to a ratiometric characteristic based on the digital signal converted by the digital signal, and the digital signal that has been corrected by the processing circuit into an analog signal A digital-to-analog converter circuit (for example, the digital-to-analog converter 503 shown in FIG. 5) that converts and outputs to the amplifier. It is desirable to include in La.

また、本発明の補正回路は、伝送路と基準伝送路との間の中間電位に関する中間電位信号を生成する中間電位信号生成手段と、センサ信号と前記中間電位信号とが供給される増幅器と、前記増幅器によって出力される信号に基づいて、アナログ電圧信号を生成するアナログ電圧信号生成手段と、を含み、前記センサ信号を前記アナログ電圧信号に変換して前記伝送路に出力する２線式伝送器の補正回路であって、前記センサ信号がセンサに与えられる電源電圧の変動に比例して信号の電圧レベルが変動する特性であるレシオメトリック特性を持つように、前記センサ信号を補正するレシオメトリック特性補正手段と、を含むことを特徴とする。 Further, the correction circuit of the present invention includes an intermediate potential signal generating means for generating an intermediate potential signal related to an intermediate potential between the transmission line and the reference transmission line, an amplifier to which the sensor signal and the intermediate potential signal are supplied, Analog voltage signal generating means for generating an analog voltage signal based on a signal output by the amplifier, and converting the sensor signal into the analog voltage signal and outputting the analog voltage signal to the transmission line And a ratiometric characteristic for correcting the sensor signal so that the sensor signal has a ratiometric characteristic in which a voltage level of the signal varies in proportion to a variation in power supply voltage applied to the sensor. And a correction means.

本発明にかかる２線式伝送器によれば、レシオメトリック特性を有するアナログ電圧信号を出力することができる。このため、２線の伝送路から信号を受ける後段のＣＰＵ等の受信機がレシオメトリック特性を有する場合でも、受信機が受けるアナログ電圧信号の精度の低下を防ぐことができる。 The two-wire transmitter according to the present invention can output an analog voltage signal having a ratiometric characteristic. For this reason, even when a receiver such as a subsequent CPU that receives a signal from a two-wire transmission line has a ratiometric characteristic, it is possible to prevent a decrease in the accuracy of the analog voltage signal received by the receiver.

本発明の実施形態１の２線式伝送器を説明するための図である。It is a figure for demonstrating the 2-wire type transmitter of Embodiment 1 of this invention. 本発明の実施形態１の２線式伝送器の動作を説明するための図である。It is a figure for demonstrating operation | movement of the two-wire transmitter of Embodiment 1 of this invention. 本発明の実施形態１の検出電圧と電源電圧の分圧との関係を示した図である。It is the figure which showed the relationship between the detection voltage of Embodiment 1 of this invention, and the partial pressure of a power supply voltage. 本発明の実施形態１のアナログ電圧信号と電源電圧との関係を示した図である。It is the figure which showed the relationship between the analog voltage signal and power supply voltage of Embodiment 1 of this invention. 本発明の実施形態２の２線式伝送器を説明するための図である。It is a figure for demonstrating the 2-wire type transmitter of Embodiment 2 of this invention. 特許文献１の２線式伝送器の従来技術を説明するための図である。It is a figure for demonstrating the prior art of the 2-wire transmitter of patent document 1. FIG. 本願発明の発明者らが発明した２線式伝送器を説明するための図である。It is a figure for demonstrating the 2-wire type transmitter which inventors of this invention invented. 特許文献２のレシオメトリック補正回路を含む回路のブロック図である。10 is a block diagram of a circuit including a ratiometric correction circuit of Patent Document 2. FIG.

以下、図面を参照して本発明の実施の形態１、実施形態２について説明する。
（実施形態１）
１回路構成
図１は、実施形態１の２線式伝送器を説明するための図であって、２線式伝送器の回路構成を示している。この２線式伝送器は、センサ１０１と、センサ１０１の出力信号Ｖsnsを増幅するオペアンプ１０２と、オペアンプ１０２の出力信号によって出力電流Ｉoutが変化する電流源１１４と、抵抗素子１０３（抵抗値Ｒ0）及び抵抗素子１０４（抵抗値Ｒ1）と、電流源１０５及び電流源１０６と、アナログ電圧信号分圧器１０７と、アナログ電圧信号の分圧を検出し、電源電圧の分圧を算出する測定器１０８と、理想的な電源電圧の分圧を生成する電圧生成器１０９と、算出された電源電圧の分圧と理想的な電源電圧の分圧からセンサ信号Ｖsnsの補正量を算出する演算器１１０と、算出された補正量に基づいてセンサ信号Ｖsnsの補正演算を行う演算器１１１と、を含んでいる。 Embodiments 1 and 2 of the present invention will be described below with reference to the drawings.
(Embodiment 1)
1 Circuit Configuration FIG. 1 is a diagram for explaining the two-wire transmitter according to the first embodiment, and shows a circuit configuration of the two-wire transmitter. The two-wire transmitter includes a sensor 101, an operational amplifier 102 that amplifies the output signal Vsns of the sensor 101, a current source 114 that changes an output current Iout according to an output signal of the operational amplifier 102, and a resistance element 103 (resistance value R0). And a resistance element 104 (resistance value R 1), a current source 105 and a current source 106, an analog voltage signal voltage divider 107, a measuring device 108 that detects the divided voltage of the analog voltage signal and calculates the divided voltage of the power supply voltage A voltage generator 109 for generating an ideal power supply voltage division, a calculator 110 for calculating a correction amount of the sensor signal Vsns from the calculated power supply voltage division and the ideal power supply voltage division, And a calculator 111 that performs a correction calculation of the sensor signal Vsns based on the calculated correction amount.

センサ１０１は、温度センサ、磁気センサ、圧力センサ等のいずれとして構成されたものであってもよい。また、図１に示した２線式伝送器は、電源電圧Ｖccを二線式伝送器に供給する電源とグランドＧＮＤとの間に、受信機１１２が抵抗素子１１３を介して接続されている。受信機１１２は、レシオメトリック特性を有するＣＰＵとして構成されている。 The sensor 101 may be configured as any of a temperature sensor, a magnetic sensor, a pressure sensor, and the like. In the two-wire transmitter shown in FIG. 1, a receiver 112 is connected via a resistance element 113 between a power supply that supplies a power supply voltage Vcc to the two-wire transmitter and a ground GND. The receiver 112 is configured as a CPU having ratiometric characteristics.

センサ１０１は、２線式伝送器と一体的に組み込まれるものであっても、別体として出荷後に２線式伝送器に接続されるものであってもよい。また、受信器１１２は、２線伝送器の出荷後、２線伝送器の後段に接続される２線伝送器とは別体の回路である。
受信機１１２にアナログ電圧信号を入力する伝送路には、二線式伝送器の出力信号であるアナログ電圧信号Ｖout1またはアナログ電圧信号Ｖout2が出力される。本明細書では、アナログ電圧信号Ｖout1、アナログ電圧信号Ｖout2の両方を指す場合、単にアナログ電圧信号Ｖoutとも記す。 The sensor 101 may be integrated with the two-wire transmitter, or may be separately connected to the two-wire transmitter after shipment. The receiver 112 is a separate circuit from the two-wire transmitter connected to the subsequent stage of the two-wire transmitter after the two-wire transmitter is shipped.
An analog voltage signal Vout1 or an analog voltage signal Vout2 that is an output signal of the two-wire transmitter is output to the transmission path for inputting the analog voltage signal to the receiver 112. In this specification, when both the analog voltage signal Vout1 and the analog voltage signal Vout2 are indicated, they are also simply referred to as an analog voltage signal Vout.

電流源１０５を流れる電流は、電源電圧Ｖccを供給する電源からグラウンドＧＮＤに流れる電流のうち、電流源１１４を流れる電流及び電流源１０６を流れる電流以外の電流の総和を示している。
図１に示した二線式伝送器において、電源電圧Ｖccを供給する電源に直接接続された伝送路を伝送路１、グラウンドＧＮＤに直接接続された伝送路を基準伝送路２と記す。オペアンプ１０２にアナログ信号Ｖrと共に入力されるフィードバック信号Ｖfbは、伝送路１と基準伝送路２との中間電位信号となる。アナログ信号Ｖr、フィードバック信号Ｖfbについては後述するものとする。 The current flowing through the current source 105 indicates the sum of currents other than the current flowing through the current source 114 and the current flowing through the current source 106 out of the current flowing from the power supply that supplies the power supply voltage Vcc to the ground GND.
In the two-wire transmitter shown in FIG. 1, a transmission line directly connected to a power source that supplies a power supply voltage Vcc is referred to as a transmission line 1, and a transmission line directly connected to the ground GND is referred to as a reference transmission line 2. A feedback signal Vfb input to the operational amplifier 102 together with the analog signal Vr is an intermediate potential signal between the transmission line 1 and the reference transmission line 2. The analog signal Vr and the feedback signal Vfb will be described later.

２動作
次に、このように構成された２線式伝送器の動作について図１と共に、図２のフローチャートを用いて説明する。先ず、実施形態１に２線式伝送器がとり得る状態Ｉ〜状態ＶＩの６つの状態について説明する。図２のフローチャートの各ステップは、状態Ｉ〜状態ＶＩの各々を実現するための動作を示している。実施形態１では、２線式伝送器が先ず状態Iを実現するように動作し（ステップＳ１）、続いて状態ＩＩを実現するよう動作する（ステップＳ２）。そして、以降、ステップＳ３〜Ｓ５を順に実行することにより、状態ＩＩＩ〜状態ＶＩが実現される。以下、状態Ｉ〜状態ＶＩの各々について、実施形態１の２線式伝送器の動作を説明する。 2 Operation Next, the operation of the two-wire transmitter configured as described above will be described with reference to the flowchart of FIG. 2 together with FIG. First, the six states of the state I to the state VI that the two-wire transmitter can take in the first embodiment will be described. Each step of the flowchart of FIG. 2 shows an operation for realizing each of the state I to the state VI. In the first embodiment, the two-wire transmitter first operates to realize state I (step S1), and then operates to realize state II (step S2). Thereafter, Steps S <b> 3 to S <b> 5 are executed in order to realize State III to State VI. Hereinafter, the operation of the two-wire transmitter of the first embodiment will be described for each of the states I to VI.

状態Ｉ
状態Ｉでは、電流源１１４の出力電流Ｉoutの出力が停止され、かつ電流源１０６に電流Ｉbias1が流される。このとき、アナログ電圧信号Ｖout1がアナログ電圧信号分圧器１０７によって１／Ｎ倍に分圧された検出電圧Ｖdet1が測定器１０８によって測定される（ステップＳ１）。 State I
In the state I, the output of the output current Iout of the current source 114 is stopped, and the current Ibias1 is supplied to the current source 106. At this time, a detection voltage Vdet1 obtained by dividing the analog voltage signal Vout1 by 1 / N times by the analog voltage signal voltage divider 107 is measured by the measuring device 108 (step S1).

状態ＩＩ
状態ＩＩでは、電流源１１４の出力電流Ｉoutの出力が停止され、かつ電流源１０６に電流Ｉbias2が流される。このとき、アナログ電圧信号Ｖout2がアナログ電圧信号分圧器１０７で１／Ｎ倍に分圧された検出電圧Ｖdet2が測定器１０８によって測定される。
検出電圧Ｖdet1は、次の式（２）で表される。式（２）においてＩcc1は電流源１０５に流れる電流である。検出電圧Ｖdet2は次の式（３）で表される。式（３）において、Ｉcc2は電流源１０５に流れる電流である（ステップＳ２）。
Ｖdet1＝Ｖout1／Ｎ=（Ｖcc−Ｒload×（Ｉcc1＋Ｉbias1））／Ｎ …式（２）
Ｖdet2＝Ｖout2／Ｎ=（Ｖcc−Ｒload×（Ｉcc2＋Ｉbias2））／Ｎ …式（３） State II
In the state II, the output of the output current Iout of the current source 114 is stopped, and the current Ibias2 is supplied to the current source 106. At this time, the measuring voltage 108 is measured by the measuring device 108, which is the detection voltage Vdet2 obtained by dividing the analog voltage signal Vout2 by 1 / N times by the analog voltage signal voltage divider 107.
The detection voltage Vdet1 is expressed by the following equation (2). In the formula (2), Icc1 is a current flowing through the current source 105. The detection voltage Vdet2 is expressed by the following equation (3). In equation (3), Icc2 is a current flowing through the current source 105 (step S2).
Vdet1 = Vout1 / N = (Vcc−Rload × (Icc1 + Ibias1)) / N (2)
Vdet2 = Vout2 / N = (Vcc-Rload × (Icc2 + Ibias2)) / N (3)

状態ＩＩＩ
状態ＩＩＩでは、測定器１０８が、検出電圧Ｖdet1と検出電圧Ｖdet2とに基づいて、電源によって印加される電源電圧Ｖccを１／Ｎ倍に分圧した電圧Ｖ1の大きさを算出する。算出は、式（２）及び式（３）によって行われる（ステップＳ３）。また、電圧Ｖ１は、以下の式（４）によって算出される。
Ｖ1＝Ｖcc／Ｎ
＝Ｖdet1＋（Ｖdet1−Ｖdet2）×（Ｉcc1＋Ｉbias1）／（Ｉcc2−Ｉcc1＋Ｉbias2−Ｉbias1） …式（４） State III
In the state III, the measuring instrument 108 calculates the magnitude of the voltage V1 obtained by dividing the power supply voltage Vcc applied by the power supply by 1 / N times based on the detection voltage Vdet1 and the detection voltage Vdet2. The calculation is performed according to equations (2) and (3) (step S3). The voltage V1 is calculated by the following equation (4).
V1 = Vcc / N
= Vdet1 + (Vdet1−Vdet2) × (Icc1 + Ibias1) / (Icc2−Icc1 + Ibias2−Ibias1) Equation (4)

ここで、電流源１０５に流れる電流Ｉcc1とＩcc2が等しく、次の式（５）で表されるとき、電源電圧Ｖccを１／Ｎに分圧した電圧Ｖ1は次の式（６）で表される。
Ｉcc1＝Ｉcc2＝Ｉcc …式（５）
Ｖ1＝Ｖdet1＋（Ｖdet1−Ｖdet2）×（Ｉcc＋Ｉbias1）／（Ｉbias2−Ｉbias1）
…式（６） Here, when the currents Icc1 and Icc2 flowing through the current source 105 are equal and expressed by the following equation (5), the voltage V1 obtained by dividing the power supply voltage Vcc by 1 / N is expressed by the following equation (6). The
Icc1 = Icc2 = Icc (5)
V1 = Vdet1 + (Vdet1-Vdet2) × (Icc + Ibias1) / (Ibias2-Ibias1)
... Formula (6)

図３は、検出電圧Ｖdet1、検出電圧Ｖdet2、及び電源電圧の分圧Ｖ1との関係を示した図である。図３の縦軸はＶout／Ｎ（すなわち検出電圧）を示している。横軸は、電流源１０５、１０６に流れる電流の和を示している。すなわち、図３によれば、電流源１０５、１０６に流れる電流の和がＩcc＋Ｉbias1のとき、Ｖout／Ｎ＝Ｖout1／Ｎ＝Ｖdet1となる。また、電流源１０５、１０６に流れる電流の和がＩcc＋Ｉbias2のとき、Ｖout／Ｎ＝Ｖout2／Ｎ＝Ｖdet2となる。そして、電流源１０５、１０６に流れる電流の和が０のとき抵抗素子１１３の両端の電位が等しくなるため、Ｖout／Ｎ＝Ｖcc／Ｎ＝Ｖ1となることが分かる。 FIG. 3 is a diagram showing the relationship between the detection voltage Vdet1, the detection voltage Vdet2, and the divided voltage V1 of the power supply voltage. The vertical axis in FIG. 3 indicates Vout / N (that is, the detection voltage). The horizontal axis represents the sum of currents flowing through the current sources 105 and 106. That is, according to FIG. 3, when the sum of the currents flowing through the current sources 105 and 106 is Icc + Ibias1, Vout / N = Vout1 / N = Vdet1. Further, when the sum of the currents flowing through the current sources 105 and 106 is Icc + Ibias2, Vout / N = Vout2 / N = Vdet2. It can be seen that when the sum of the currents flowing through the current sources 105 and 106 is 0, the potentials at both ends of the resistance element 113 are equal, so that Vout / N = Vcc / N = V1.

状態ＩＶ
状態ＩＶでは、演算器１１０により、電源の電圧Ｖccの分圧Ｖ1と理想的な電源電圧の分圧Ｖ0に応じてセンサ信号Ｖsnsの補正量Ｖcが算出される（ステップＳ４）。電圧生成器１０９によって理想的な電源電圧Ｖcc0を１／Ｎ倍に分圧した電圧Ｖ0が生成されるとき、センサ信号Ｖsnsの補正量Ｖcは次の式（７）で表される。
Ｖc＝Ｖ1／Ｖ0＝Ｖcc／Ｖcc0 …式（７）
なお、理想的な電源電圧の分圧Ｖ0、センサ信号Ｖsnsの補正量Ｖcの算出は、２線式伝送器の出荷後、センサや電源、外部制御装置となるコンピュータ等に２線式伝送器を接続し、未だ２線式伝送器が２線式伝送器として動作していないとき等に行われる。そして、算出された補正量Ｖcは演算器１１０の図示しないＲＡＭ等に書き込まれ、以降繰返しセンサ信号Ｖsnsの補正に使用される。 State IV
In the state IV, the calculator 110 calculates the correction amount Vc of the sensor signal Vsns according to the divided voltage V1 of the power supply voltage Vcc and the ideal divided voltage V0 of the power supply voltage (step S4). When the voltage generator 109 generates a voltage V0 obtained by dividing the ideal power supply voltage Vcc0 by 1 / N times, the correction amount Vc of the sensor signal Vsns is expressed by the following equation (7).
Vc = V1 / V0 = Vcc / Vcc0 (7)
Note that the ideal power supply voltage division V0 and sensor signal Vsns correction amount Vc are calculated after the 2-wire transmitter is shipped after the 2-wire transmitter is installed in the sensor, power supply, external control computer, etc. For example, when the two-wire transmitter is not yet operating as a two-wire transmitter. Then, the calculated correction amount Vc is written in a RAM (not shown) of the arithmetic unit 110 and thereafter used repeatedly for correcting the sensor signal Vsns.

状態Ｖ
状態Ｖでは、演算器１１１が、センサ信号Ｖsnsと補正量Ｖcとを乗算し、アナログ信号Ｖrを算出する（ステップＳ５）。アナログ信号Ｖrは次の式（８）で表される。
Ｖr＝Ｖsns×Ｖc＝Ｖsns×Ｖcc／Ｖcc0 …式（８）
式（８）によれば、アナログ信号Ｖrが電源電圧Ｖccに比例していることがわかる。すなわち、アナログ信号Ｖrはレシオメトリック特性を有することが明らかである。 State V
In the state V, the computing unit 111 multiplies the sensor signal Vsns and the correction amount Vc to calculate the analog signal Vr (step S5). The analog signal Vr is expressed by the following equation (8).
Vr = Vsns × Vc = Vsns × Vcc / Vcc0 (8)
According to equation (8), it can be seen that the analog signal Vr is proportional to the power supply voltage Vcc. That is, it is clear that the analog signal Vr has a ratiometric characteristic.

状態ＶＩ
状態ＶＩでは、オペアンプ１０２がアナログ信号Ｖrとフィードバック信号Ｖfbが等しくなるように電流源１１４の出力電流Ｉoutを制御する。出力電流Ｉoutが制御されることにより、アナログ電圧信号Ｖoutが出力される（ステップＳ６）。センサ信号Ｖsnsとアナログ電圧信号Ｖoutの関係は次の式（９）で表される。
Ｖout＝（１＋（Ｒ0／Ｒ1））×Ｖr
＝（１＋（Ｒ0／Ｒ1））×Ｖsns×Ｖcc／Ｖcc0 …式（９） State VI
In the state VI, the operational amplifier 102 controls the output current Iout of the current source 114 so that the analog signal Vr and the feedback signal Vfb are equal. By controlling the output current Iout, the analog voltage signal Vout is output (step S6). The relationship between the sensor signal Vsns and the analog voltage signal Vout is expressed by the following equation (9).
Vout = (1+ (R0 / R1)) × Vr
= (1+ (R0 / R1)) × Vsns × Vcc / Vcc0 Equation (9)

式（９）によれば、アナログ電圧信号Ｖoutが電源電圧Ｖccに比例していることがわかる。図４は、アナログ電圧信号Ｖoutと電源電圧Ｖccとの関係を示した図であって、縦軸にアナログ電圧信号Ｖout、横軸に電源電圧Ｖccが示されている。図４によれば、アナログ電圧信号Ｖoutが電源電圧Ｖccに比例して変化する、レシオメトリック特性を有することが明らかである。 According to equation (9), it can be seen that the analog voltage signal Vout is proportional to the power supply voltage Vcc. FIG. 4 is a diagram showing the relationship between the analog voltage signal Vout and the power supply voltage Vcc. The vertical axis shows the analog voltage signal Vout, and the horizontal axis shows the power supply voltage Vcc. According to FIG. 4, it is clear that the analog voltage signal Vout has a ratiometric characteristic that changes in proportion to the power supply voltage Vcc.

以上説明した実施形態１によれば、レシオメトリック型の２線式伝送器を提供することができるので、レシオメトリック特性を有する受信機を適用した場合であっても、レシオメトリック補正回路を用いることなく受信機にレシオメトリック特性を有するアナログ電圧信号を出力し、受信機における信号処理の精度が低下することを防ぐことができる。 According to the first embodiment described above, a ratiometric type two-wire transmitter can be provided, and therefore, even when a receiver having a ratiometric characteristic is applied, a ratiometric correction circuit is used. Therefore, an analog voltage signal having a ratiometric characteristic can be output to the receiver, and the signal processing accuracy in the receiver can be prevented from being lowered.

（実施形態２）
図５は、実施形態２の２線式伝送器を説明するための図である。なお、実施形態２では、図５中に示した構成のうち、図２に示した構成と同様の構成については同様の符号を付し、説明を一部略するものとする。
実施形態２の２線式伝送器は、図１に示した実施形態１の２線式伝送器に、アナログ・デジタル変換器５０１、５０２、デジタル演算器５００、デジタル・アナログ変換器５０３を追加して構成されている。デジタル演算器５００は、図１に示した電源電圧の分圧を算出する測定器１０８、理想的な電源電圧の分圧を生成する電圧生成器１０９、算出された電源電圧の分圧と理想的な電源電圧の分圧からセンサ信号Ｖsnsの補正量を算出する演算器１１０、算出された補正量に基づいてセンサ信号Ｖsnsの補正演算を行う演算器１１１によって構成されている。 (Embodiment 2)
FIG. 5 is a diagram for explaining the two-wire transmitter according to the second embodiment. In the second embodiment, among the configurations shown in FIG. 5, configurations similar to those shown in FIG. 2 are denoted by the same reference numerals, and description thereof is partially omitted.
In the two-wire transmitter of the second embodiment, analog / digital converters 501 and 502, a digital arithmetic unit 500, and a digital / analog converter 503 are added to the two-wire transmitter of the first embodiment shown in FIG. Configured. The digital arithmetic unit 500 includes a measuring unit 108 that calculates the divided voltage of the power supply voltage shown in FIG. 1, a voltage generator 109 that generates a divided voltage of the ideal power supply voltage, and an ideal divided voltage of the calculated power supply voltage. The calculator 110 calculates the correction amount of the sensor signal Vsns from the divided power supply voltage, and the calculator 111 performs the correction calculation of the sensor signal Vsns based on the calculated correction amount.

実施形態２のアナログ電圧信号Ｖoutはアナログ・デジタル変換器５０２によってデジタル信号に変換される。変換後のデジタル信号は測定器１０８と電圧生成器１０９と演算器によって補正量Ｖcに変換される。センサ信号Ｖsnsはアナログ・デジタル変換器ADC1によってデジタル信号に変換される。変換後のデジタル信号は演算器１１１によって補正量Ｖcと乗算された後、デジタル・アナログ変換器５０３によってアナログ信号Ｖrに変換される。このような実施形態２によれば、センサ信号Ｖsnsをアナログ信号Ｖrに変換した後に、実施形態１と同様の処理をすることができる。 The analog voltage signal Vout of the second embodiment is converted into a digital signal by the analog / digital converter 502. The converted digital signal is converted into a correction amount Vc by the measuring device 108, the voltage generator 109, and the arithmetic unit. The sensor signal Vsns is converted into a digital signal by the analog / digital converter ADC1. The converted digital signal is multiplied by the correction amount Vc by the arithmetic unit 111 and then converted to the analog signal Vr by the digital / analog converter 503. According to the second embodiment, after the sensor signal Vsns is converted into the analog signal Vr, the same processing as that of the first embodiment can be performed.

以上説明した本発明は、センサによって検出された検出値を反映して連続的に変化する、レシオメトリック特性を有する信号を得ることが望ましい２線式伝送器であれば、どのような２線式伝送器にも適用することができる。 The present invention described above can be any two-wire transmitter as long as it is desirable to obtain a signal having a ratiometric characteristic that continuously changes to reflect a detection value detected by a sensor. It can also be applied to a transmitter.

１０１センサ
１０２オペアンプ
１０３，１０４，１１３抵抗素子
１０４抵抗素子
１０５，１０６，１１４電流源
１０７アナログ電圧信号分圧器
１０８測定器
１０９電圧生成器
１１０演算器
１１２受信機
５００デジタル演算器
５０１，５０２アナログ・デジタル変換器
５０３デジタル・アナログ変換器 DESCRIPTION OF SYMBOLS 101 Sensor 102 Operational amplifier 103,104,113 Resistance element 104 Resistance element 105,106,114 Current source 107 Analog voltage signal voltage divider 108 Measuring instrument 109 Voltage generator 110 Calculator 112 Receiver 500 Digital calculator 501 and 502 Analog digital Converter 503 Digital / analog converter

Claims

A two-wire transmitter that converts a sensor signal into an analog voltage signal and outputs it to a transmission line,
Intermediate potential signal generating means for generating an intermediate potential signal related to an intermediate potential between the transmission path and a reference transmission path;
An amplifier to which the sensor signal and the intermediate potential signal are supplied;
Analog voltage signal generating means for generating the analog voltage signal based on a signal output by the amplifier;
Ratiometric characteristic correction means for correcting the sensor signal so that the sensor signal has a ratiometric characteristic that is a characteristic in which the voltage level of the signal varies in proportion to a variation in power supply voltage applied to the sensor;
A two-wire transmitter comprising:

The ratiometric characteristic correcting means includes
Correction calculation means for performing correction calculation of the analog voltage signal so that the sensor signal has a ratiometric characteristic that is a characteristic in which the voltage level of the signal varies in proportion to a variation in power supply voltage applied to the sensor;
Correction amount calculating means for calculating a correction amount used for correction by the correction calculating means;
The two-wire transmitter according to claim 1, comprising:

The correction amount calculating means includes
When the operation as a two-wire transmitter for converting the sensor signal into an analog voltage signal and outputting it to a transmission line is not performed, a correction amount used for correction by the correction calculation means is calculated. The two-wire transmitter according to claim 2.

The correction calculation means includes
Bias current generating means;
Means for dividing the analog voltage signal;
Calculating means for detecting a divided voltage of the analog voltage signal and calculating a divided voltage of a power supply voltage based on the divided voltage of the bias current and the analog voltage signal;
Means for generating a voltage corresponding to the ideal power supply voltage division;
A calculation means for calculating a correction amount of the analog voltage signal according to a calculated value of the divided voltage of the power supply voltage and a voltage corresponding to an ideal divided voltage of the power supply voltage;
Arithmetic means for performing a correction calculation of the analog voltage signal based on the correction amount;
The two-wire transmitter according to claim 2, wherein the two-wire transmitter is included.

The ratiometric characteristic correcting unit is configured to divide a power supply voltage based on a first detection voltage measured by flowing a first current and a second detection voltage measured by flowing a second current. The two-wire transmitter according to claim 1, wherein the two-wire transmitter is calculated.

2. The ratiometric characteristic correcting unit calculates a correction amount of an analog voltage signal in accordance with a voltage corresponding to the calculated divided power supply voltage and an ideal divided power supply voltage. 6. A two-wire transmitter according to any one of items 1 to 5.

The two-wire transmitter according to claim 1, wherein the ratiometric characteristic correcting unit multiplies the correction amount by the sensor signal.

The amplifier is supplied with the sensor signal and the intermediate potential signal, and controls the potential between the transmission line and the reference transmission line so that the input sensor signal and the intermediate potential signal are equal. The two-wire transmitter according to claim 1, wherein a signal to be output is output.

When the sensor signal is an analog signal, a first conversion circuit that converts the sensor signal into a digital signal;
A second conversion circuit for converting the divided voltage of the analog voltage signal into a digital signal;
A processing circuit that outputs a digital signal corrected to a ratiometric characteristic based on the digital signals converted by the first and second conversion circuits, and a digital signal corrected by the processing circuit is converted into an analog signal. A digital-to-analog converter circuit for outputting to the amplifier;
The two-wire transmitter according to claim 1, further comprising:

Based on an intermediate potential signal generating means for generating an intermediate potential signal relating to an intermediate potential between the transmission path and the reference transmission path, an amplifier to which a sensor signal and the intermediate potential signal are supplied, and a signal output by the amplifier An analog voltage signal generating means for generating an analog voltage signal, and a correction circuit for a two-wire transmitter that converts the sensor signal into the analog voltage signal and outputs the analog voltage signal to the transmission line,
Ratiometric characteristic correcting means for correcting the sensor signal so that the sensor signal has a ratiometric characteristic that is a characteristic in which the voltage level of the signal varies in proportion to a variation in power supply voltage applied to the sensor;
A correction circuit comprising: