JPH07152989A - Two-wire communication device - Google Patents
Two-wire communication deviceInfo
- Publication number
- JPH07152989A JPH07152989A JP31928493A JP31928493A JPH07152989A JP H07152989 A JPH07152989 A JP H07152989A JP 31928493 A JP31928493 A JP 31928493A JP 31928493 A JP31928493 A JP 31928493A JP H07152989 A JPH07152989 A JP H07152989A
- Authority
- JP
- Japan
- Prior art keywords
- signal
- transmitter
- receiving
- current
- external sensor
- 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.)
- Granted
Links
Landscapes
- Arrangements For Transmission Of Measured Signals (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、工業用プロセスの現場
に置かれた発信器からの信号を２線の信号線を介して計
器室側の受信器に送信するシステムであって、発信器に
他のセンサを接続して、複数の信号を送信可能にした２
線式通信装置に関するものである。特に、既存の２線式
の発信器を単独で具備したシステムに外部センサを追加
する場合の技術に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system for transmitting a signal from an oscillator placed at a site of an industrial process to a receiver on the instrument room side through two signal lines. Connected to other sensor to enable multiple signals 2
The present invention relates to a wire communication device. In particular, the present invention relates to a technique for adding an external sensor to a system having an existing 2-wire oscillator alone.
【０００２】[0002]
【従来の技術】第２図は、従来の発信器を単独で用いた
２線式通信装置の回路を示したものである。２１は差圧
発信器、電磁流量計等の発信器であって、測定物理量を
４〜２０ｍＡの電流信号をデジタル信号で信号線２３、
２３’を介して発信する発信器である。２４は通常受信
計器室側に設置される電源で、一般的には２４Ｖのもの
が多く用いられる。２５は前記発信器２１が発信した信
号を受信するための受信抵抗で、４〜２０ｍＡの信号を
受信する時に、次に接続されるコントローラ等の受信計
器の関係から１〜５Ｖの電圧値で受信するため、通常は
２５０Ωの抵抗が用いられる。2. Description of the Related Art FIG. 2 shows a circuit of a two-wire type communication device using a conventional oscillator alone. Reference numeral 21 is a transmitter such as a differential pressure transmitter or an electromagnetic flow meter, which uses a digital signal for a current signal having a measured physical quantity of 4 to 20 mA as a signal line 23,
It is a transmitter which transmits via 23 '. 24 is a power source normally installed on the receiving instrument room side, and in general, a power source of 24 V is often used. Reference numeral 25 is a receiving resistor for receiving the signal transmitted by the transmitter 21, and when receiving a signal of 4 to 20 mA, it is received at a voltage value of 1 to 5 V due to the relation of a receiving instrument such as a controller connected next. Therefore, a resistance of 250Ω is usually used.
【０００３】発信器２１は、測定信号を例えば０〜１０
０％の数値で発信する場合、デジタル信号で４ｍＡと２
０ｍＡを０、１にそれぞれ対応させて予め決められた通
信プロトコルに従って数値をデジタル化し発信する。こ
のときの最低値４ｍＡが発信器２１の駆動電流となり、
他に電源を取る必要がないのがこれら通信装置の特徴で
もある。The transmitter 21 sends a measurement signal to, for example, 0-10.
When transmitting with a numerical value of 0%, 4 mA and 2 are digital signals.
Numerical values are digitized and transmitted according to a predetermined communication protocol in which 0 mA is associated with 0 and 1, respectively. At this time, the minimum value of 4 mA becomes the drive current of the oscillator 21,
Another feature of these communication devices is that they do not need to be powered.
【０００４】なお、ここで示した装置および４〜２０ｍ
Ａ、１〜５Ｖという数値は、それまで用いられていたア
ナログ信号を発信するための通信装置を、そのままデジ
タル信号を発信する装置に用いたために、そのときの信
号等の値がそのまま用いられている。これによって両通
信方式を併用することも可能となっている。The device shown here and 4 to 20 m
The numerical values of A and 1 to 5V are used because the communication device for transmitting an analog signal, which has been used up to that point, is used as it is for a device for transmitting a digital signal. There is. This makes it possible to use both communication methods together.
【０００５】発信器２１により発信された信号は受信抵
抗２５により１〜５Ｖの電圧信号に変換されるが、信号
線はプロセス現場まで引き回されるので、受信抵抗によ
る電圧降下の最高値である５Ｖより十分高い電圧が必要
となり、２４Ｖという電圧の電源が用いられている。The signal transmitted by the transmitter 21 is converted into a voltage signal of 1 to 5 V by the receiving resistor 25, but since the signal line is routed to the process site, it is the maximum voltage drop due to the receiving resistor. A voltage sufficiently higher than 5V is required, and a power source having a voltage of 24V is used.
【０００６】[0006]
【発明が解決しようとする課題】以上のような通信装置
においては、発信器の高機能化および、デジタルで信号
を発信する構造であるため、発信器によって測定された
物理量の他に別の情報も送信出来るようになった。従っ
て発信器の状態等の情報も同時に送信出来るが、その他
にも発信器付近にある外部センサの信号も同時に発信器
内に取り込み送信することも可能となった。In the communication device as described above, since the transmitter has a high function and has a structure for transmitting a signal digitally, other information besides the physical quantity measured by the transmitter is provided. Can also be sent. Therefore, information such as the status of the transmitter can be transmitted at the same time, but in addition to this, the signals of external sensors near the transmitter can also be captured and transmitted to the transmitter at the same time.
【０００７】ところが、外部センサ自身も電源が必要で
あり、そのために新たに電源配線を引くことは費用の無
駄となる。従って、この電源を通信装置の２線の信号線
から発信器と同様に取れればよいが、その電流の増加分
だけ受信抵抗での電圧降下が増加する。例えば、センサ
が４０ｍＡの電源を必要とするときに、これが４〜２０
ｍＡと重畳すると４４〜６０ｍＡとなるので、受信抵抗
（２５０Ω）の両端には１１〜１５Ｖの電圧を発生す
る。However, since the external sensor itself also needs a power source, it is costly to draw a new power source wiring. Therefore, this power source can be taken from the two signal lines of the communication device in the same manner as the oscillator, but the voltage drop at the receiving resistance increases by the increase in the current. For example, when the sensor requires 40 mA of power, this can be 4-20
Since it becomes 44 to 60 mA when superposed on mA, a voltage of 11 to 15 V is generated across the receiving resistor (250Ω).
【０００８】しかし、従来の回路のままであると電源電
圧が２４Ｖであるので、電圧不足が生じ遠距離の伝送が
困難になって、プロセス機器としての用を成さなくなる
可能性があった。従って、外部センサを接続する度に、
電源をさらに高圧のものに取り替えなければならないと
いう欠点があった。また、受信抵抗に生ずる電圧が高く
なるので、後段の機器の為に電圧調整も必要になってい
た。However, if the conventional circuit is used as it is, the power supply voltage is 24 V, so that there is a possibility that voltage shortage occurs and it becomes difficult to transmit over a long distance, and it cannot be used as a process device. Therefore, each time you connect an external sensor,
There was a drawback that the power supply had to be replaced with a higher voltage one. In addition, since the voltage generated in the receiving resistance becomes high, it is necessary to adjust the voltage for the equipment in the subsequent stage.
【０００９】消費電流の小さい外部センサを用いること
も考えられるが、そのための外部センサを新たに設ける
ことは更に手間がかかり、本来のコスト、手間を省く目
的に反してしまう。従って従来からある任意のセンサを
用いることができることも目的の一つとなる。Although it is conceivable to use an external sensor that consumes a small amount of current, it is more laborious to newly provide an external sensor for that purpose, which goes against the original cost and the purpose of saving labor. Therefore, it is also one of the purposes that any conventional sensor can be used.
【００１０】[0010]
【課題を解決するための手段】そこで、本発明はこれら
の問題を解決するために、２線の信号線を介して４〜２
０ｍＡの電流信号を発信する発信器と、該発信器に接続
され、駆動電流を上記信号線より受け、かつ測定信号を
前記発信器に送出する外部センサと、前記２線の信号線
の受信側に接続される電源と、前記発信器からの信号を
電圧として受信するための受信抵抗と、該受信抵抗と並
列に接続され、発信器からの電流が前記外部センサの使
用により、その消費電流分だけ増加したときにその増加
分の電流を流す定電流回路とにより装置を構成した。Therefore, in order to solve these problems, the present invention uses 4 to 2 through 2 signal lines.
A transmitter for transmitting a current signal of 0 mA, an external sensor connected to the transmitter for receiving a drive current from the signal line and transmitting a measurement signal to the transmitter, and a receiving side for the two signal lines. Connected to the power source, a receiving resistance for receiving a signal from the oscillator as a voltage, and a current connected to the receiving resistor in parallel, and the current from the oscillator is consumed by the use of the external sensor. The device was configured with a constant current circuit that supplies a current for the increased amount.
【００１１】[0011]
【作用】以上のような装置により、外部センサの消費電
流が発信器の信号電流に重畳した場合、定電流回路によ
り外部センサの消費電流分の電流をバイパスし、受信抵
抗の両端の電圧が外部センサのない状態まで下がる。従
って、電源、受信抵抗およびその後段の受信計器は何ら
変更する必要がなく、線間電圧も変わらないので伝送に
必要な電圧は十分な値が確保できる。With the above device, when the current consumption of the external sensor is superimposed on the signal current of the transmitter, the constant current circuit bypasses the current consumption amount of the external sensor, and the voltage across the receiving resistor becomes external. It goes down to the state without a sensor. Therefore, it is not necessary to change the power supply, the receiving resistance, and the receiving instrument in the subsequent stage, and the line voltage does not change, so that a sufficient voltage can be secured for transmission.
【００１２】[0012]
【実施例】第１図に本発明の一実施例を示して説明す
る。１はマイコンを内蔵した差圧発信器であって、従来
のアナログ発信に加えてデジタル発信も可能であり、内
部の差圧以外の情報、例えば静圧や温度の情報を同時に
発信できるような構成を持っている。また、外部に他の
センサ、例えば差圧発信器により流量を測定するとき
に、流体の温度を測定することで補正をする場合などの
温度センサ等の信号を入力できる端子を有している。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. Reference numeral 1 is a differential pressure transmitter with a built-in microcomputer, which is capable of digital transmission in addition to conventional analog transmission, and is capable of transmitting information other than internal differential pressure, such as static pressure and temperature information at the same time. have. Further, it has a terminal to which a signal of a temperature sensor or the like can be input externally when another sensor such as a differential pressure transmitter is used to make a correction by measuring the temperature of the fluid.
【００１３】４は２４Ｖの電源であり、従来と同等のも
のを使用する。これは発信器単独でデジタル発信してい
る場合も、アナログ発信を行っている場合も、通常２４
Ｖ程度の電圧の電源が用いられている。これは長距離伝
送に十分な信号伝送電圧を確保するためのものである。Reference numeral 4 is a 24 V power source, which is equivalent to the conventional one. This is usually 24 regardless of whether the transmitter is making digital transmission or analog transmission.
A power supply with a voltage of about V is used. This is to ensure a sufficient signal transmission voltage for long distance transmission.
【００１４】５は、受信抵抗であり受信計器６例えばコ
ントローラや記録計等が両端に接続され、４〜２０ｍＡ
に対して２５０Ωの抵抗を接続し、１〜５Ｖの電圧に変
換され前記受信計器６に信号が与えれる。本発明におい
てはデジタル信号で検出信号が与えれている。従って、
信号には発信器からのプロセス信号の他に時分割で他の
情報、例えば発信器１が複合センサの場合は他のプロセ
ス信号や、発信器１の診断情報等も所定のプロトコルで
発信可能である。Reference numeral 5 denotes a receiving resistor, which is connected to both ends of a receiving instrument 6 such as a controller or a recorder, and has a capacity of 4 to 20 mA.
A resistor of 250 Ω is connected to the above, and the voltage is converted to a voltage of 1 to 5 V and a signal is given to the receiving instrument 6. In the present invention, the detection signal is given as a digital signal. Therefore,
In addition to the process signal from the oscillator, other information can be transmitted in a time-division manner in a predetermined protocol, for example, when the oscillator 1 is a composite sensor, other process signals and diagnostic information of the oscillator 1 can be transmitted. is there.
【００１５】２は、本願発明で要求される外部センサで
ある。２線の信号線３、３’に並列に挿入することで電
源を受け、駆動される。測定信号は前記差圧発信器１の
端子に入力される。ここで用いられるセンサは、例えば
発信器１が差圧発信器であって、流体の流量を測定する
場合、流体の温度が流量の測定に影響を与えるため、温
度補正が必要になる場合がある。その場合、その流体の
温度を測定するため、配管に挿入される温度センサのよ
うなものである。ところが従来は、その測定信号を計器
室まで別の信号線を用いて送信すると共に電源線も別に
設けたりした。そしてそのための配線の手間やコストは
膨大であった。Reference numeral 2 is an external sensor required in the present invention. By inserting the two signal lines 3 and 3'in parallel, the power is received and driven. The measurement signal is input to the terminal of the differential pressure transmitter 1. In the sensor used here, for example, when the transmitter 1 is a differential pressure transmitter and the flow rate of the fluid is measured, the temperature of the fluid affects the measurement of the flow rate, and thus temperature correction may be necessary. . In that case, it is like a temperature sensor inserted in the pipe to measure the temperature of the fluid. However, conventionally, the measurement signal is transmitted to the instrument room using another signal line, and a power supply line is separately provided. And the labor and cost of the wiring for that were enormous.
【００１６】本願発明では、発信器１がデジタル信号に
より複数の信号が発信可能であるので、外部センサ２の
信号を発信器１の外部信号入力端子に入力し、発信器１
の信号と共に測定信号を発信する。また、電源も発信器
１の信号線から受けることによって、電源の問題も解決
する。In the present invention, since the oscillator 1 is capable of transmitting a plurality of signals by digital signals, the signal of the external sensor 2 is input to the external signal input terminal of the oscillator 1, and the oscillator 1
The measurement signal is transmitted together with the signal of. Also, by receiving the power source from the signal line of the oscillator 1, the power source problem can be solved.
【００１７】ところが、外部センサ２の電源を発信器に
並列に接続すると、４〜２０ｍＡに重畳して外部センサ
２の消費電流４０ｍＡが加わるため、信号電流は４４〜
６０ｍＡとなる。ところで、受信計器６の受けられる電
圧信号は１〜５Ｖでり、２５０Ωで受けることは不可能
であることと、外部センサ２の消費する電流４０ｍＡは
変化がないことにより、受信抵抗５に並列に接続された
定電流回路７を介して外部センサ２の消費電流分４０ｍ
Ａを迂回するよう調整しておけば、受信抵抗５の両端に
は信号分の電圧のみが発生し、結局、受信抵抗５の両端
に発生する電圧は変わらない。However, when the power source of the external sensor 2 is connected in parallel to the oscillator, the consumption current of the external sensor 2 of 40 mA is superimposed on 4 to 20 mA and the signal current is 44 to 40 mA.
It becomes 60mA. By the way, the voltage signal received by the receiving instrument 6 is 1 to 5 V, it is impossible to receive it at 250 Ω, and the current 40 mA consumed by the external sensor 2 does not change. 40m of current consumption of the external sensor 2 via the connected constant current circuit 7
If the voltage is adjusted so as to bypass A, only the voltage for the signal is generated at both ends of the receiving resistor 5, and the voltage generated at both ends of the receiving resistor 5 remains unchanged.
【００１８】従って、発信器１に接続した外部センサの
消費電流は予め分かっているので、その消費電流分を定
電流回路６で流すことにより、受信計器６側では物理的
な変更は何ら必要なくなる。つまり、従来の通信装置の
構成に既存の外部センサと、電流調整可能な定電流回路
を接続することで本発明の装置が実現する。Therefore, since the current consumption of the external sensor connected to the transmitter 1 is known in advance, by making the current consumption flow in the constant current circuit 6, no physical change is required on the receiving instrument 6 side. . That is, the device of the present invention is realized by connecting the existing external sensor to the configuration of the conventional communication device and the constant current circuit capable of adjusting the current.
【００１９】ただし、外部センサが加わったため、発信
器１から出力される信号には、その測定信号が乗るの
で、それを分離する回路、もしくはソフトウエアが必要
となる。However, since an external sensor is added, the signal output from the oscillator 1 carries the measurement signal, so that a circuit or software for separating it is required.
【００２０】[0020]
【発明の効果】以上説明したように、本願発明により、
従来の２線式通信の基本的構成は一切変更することな
く、外部センサ２と定電流回路７を接続するだけで構成
できるので非常に簡単であり、コスト的にも有利であ
る。また、電源電圧も従来のままで伝送に何ら影響を与
えることもない。As described above, according to the present invention,
Since the basic configuration of the conventional two-wire communication can be configured by simply connecting the external sensor 2 and the constant current circuit 7 without any change, it is very simple and advantageous in terms of cost. Further, the power supply voltage remains unchanged and does not affect the transmission at all.
【００２１】更に、前記構成は複数の外部センサを用い
ても何ら基本的構成に変わるところがなく、定電流回路
７の調整をするだけで信号線の許容電流の許す限り外部
センサを追加することがきる。Furthermore, even if a plurality of external sensors are used, the above-mentioned structure does not change to the basic structure at all, and the external sensor can be added only by adjusting the constant current circuit 7 as long as the allowable current of the signal line permits. Wear.
【図１】本発明を適用した装置の一実施例を示す図FIG. 1 is a diagram showing an embodiment of an apparatus to which the present invention is applied.
【図２】従来の通信装置の構成を示す図FIG. 2 is a diagram showing a configuration of a conventional communication device.
１ 発信器 ２ 外部センサ ３ 信号線 ４ 電源 ５ 受信抵抗 ６ 受信計器 ７ 定電流回路 1 transmitter 2 external sensor 3 signal line 4 power supply 5 receiving resistance 6 receiving instrument 7 constant current circuit
Claims (1)
信号を発信する発信器と、該発信器に接続され、駆動電
流を前記信号線より受け、かつ測定信号を前記発信器に
送出する外部センサと、前記２線の信号線の受信側に接
続される電源と、前記発信器からの信号を電圧として受
信するための受信抵抗と、該受信抵抗と並列に接続さ
れ、発信器からの電流が前記外部センサの使用により、
その消費電流分だけ増加したときにその増加分の電流を
流す定電流回路とを備えたことを特徴とする２線式通信
装置。1. An oscillator for transmitting a current signal of 4 to 20 mA through two signal lines, and a transmitter connected to the oscillator for receiving a drive current from the signal line and receiving a measurement signal in the oscillator. An external sensor for transmitting, a power source connected to the receiving side of the two-wire signal line, a receiving resistor for receiving a signal from the oscillator as a voltage, and a transmitter connected in parallel with the receiving resistor, Current from the use of the external sensor,
A two-wire communication device comprising: a constant current circuit that causes a current to flow when the current consumption increases.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP31928493A JP2928970B2 (en) | 1993-11-26 | 1993-11-26 | Two-wire communication device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP31928493A JP2928970B2 (en) | 1993-11-26 | 1993-11-26 | Two-wire communication device |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH07152989A true JPH07152989A (en) | 1995-06-16 |
| JP2928970B2 JP2928970B2 (en) | 1999-08-03 |
Family
ID=18108492
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP31928493A Expired - Fee Related JP2928970B2 (en) | 1993-11-26 | 1993-11-26 | Two-wire communication device |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2928970B2 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2005122744A (en) * | 2003-10-14 | 2005-05-12 | Rosemount Inc | Two-line processing device installed on work site |
| WO2012009178A1 (en) * | 2010-07-15 | 2012-01-19 | Metrix Instrument Co., Lp | Dual wire dynamic proximity transducer interface for use in proximity transducer system and proximity transducer system including the same |
-
1993
- 1993-11-26 JP JP31928493A patent/JP2928970B2/en not_active Expired - Fee Related
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2005122744A (en) * | 2003-10-14 | 2005-05-12 | Rosemount Inc | Two-line processing device installed on work site |
| JP4722447B2 (en) * | 2003-10-14 | 2011-07-13 | ローズマウント インコーポレイテッド | Signal converter |
| WO2012009178A1 (en) * | 2010-07-15 | 2012-01-19 | Metrix Instrument Co., Lp | Dual wire dynamic proximity transducer interface for use in proximity transducer system and proximity transducer system including the same |
| US9464880B2 (en) | 2010-07-15 | 2016-10-11 | Metrix Instrument Co., Lp | Dual wire dynamic proximity transducer interface for use in proximity transducer system and proximity transducer system including the same |
Also Published As
| Publication number | Publication date |
|---|---|
| JP2928970B2 (en) | 1999-08-03 |
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