WO2003005319A1 - Intrinsically safe explosion-proof sensor circuit - Google Patents
Intrinsically safe explosion-proof sensor circuit Download PDFInfo
- Publication number
- WO2003005319A1 WO2003005319A1 PCT/JP2001/005835 JP0105835W WO03005319A1 WO 2003005319 A1 WO2003005319 A1 WO 2003005319A1 JP 0105835 W JP0105835 W JP 0105835W WO 03005319 A1 WO03005319 A1 WO 03005319A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- sensor
- operational amplifier
- current limiting
- circuit
- proof
- Prior art date
Links
Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
- H02H9/008—Intrinsically safe circuits
Definitions
- the present invention drives a sensor that measures pressure, temperature, and other physical quantities having a resistive or capacitive impedance by supplying a constant power from the outside, and receives a response signal from the sensor unit.
- the present invention relates to a sensor signal processing circuit extracted as a function of a measured physical quantity, and more particularly to a sensor signal processing circuit for realizing an explosion-proof structure for limiting accident energy supplied to a sensor element disposed in a hazardous area.
- a sensor having an impedance corresponding to the physical quantity of the device under test is passive without itself having an energy source, and it is necessary to apply driving power from outside the sensor. Therefore, in order to realize intrinsically safe explosion-proof, large-scale ones that include a circuit for maintaining safety in a non-hazardous area and that consist of a resistor for limiting current and voltage, a Zener diode, and a fuse have been widely used. I have.
- the drive power supply structure of the sensor element is generally driven by a DC power supply, Since the change has a large effect on the sensor accuracy, it was difficult to avoid the effect.
- the present invention it is possible to limit the voltage and the current applied to the sensor element disposed in the hazardous area to the limit that does not generate energy that ignites and explodes due to sparks, arcs, heat or the like generated electrically.
- the purpose is to provide a small-sized, low-cost, and simple configuration that allows the safe maintenance circuit to be installed in a non-hazardous area or inside the instrument in a flameproof structure case. Disclosure of the invention
- FIG. 1 and FIG. 2 show the overall configuration for implementing the present invention.
- a sensor element is installed in a hazardous area
- a safety circuit and a main body of the instrument are installed in a non-hazardous area (Fig. 1) or a safety area (Fig. 2) in a danger area but a flameproof structure case.
- Fig. 1 or Fig. 2 a non-hazardous area
- Fig. 2 a safety area
- Fig. 2 a safety area in a danger area but a flameproof structure case.
- a method is adopted in which only sensor elements that do not have a power supply have an intrinsically safe explosion-proof structure.
- Fig. 3 shows a circuit system that maintains safety with a current limiting resistor. This limits the energy flowing to the hazardous area by the current limiting resistor even when a high voltage, which is the maximum expected voltage at the time of a fault, for example, 25 OV (DC or commercial 50/60 Hz) is applied. It's what you do.
- the voltage may be limited separately (not shown) by a Zener diode, or the energy may be limited only by limiting the current without limiting the voltage.
- the current value obtained including not only the impedance ZS of the sensor but also the current limiting resistance impedance R h is expressed by Equation (1) according to Thevenin's theorem.
- the current limiting resistance R h changes with temperature. In such a case, a measurement error occurs because the noise component increases.
- the first means is to provide operational amplifiers for driving and feedback at both ends of the signal line from the sensor terminal so that the impedance of the current limiting resistor can be ignored.
- the operational amplifiers are ideal hereinafter, and that the open gain Av of the operational amplifier is infinite, the input impedance is infinite, and the output impedance is 0. If the sensor terminals are point A and point ⁇ , respectively, the voltage at point ⁇ is given by the following equation (2).
- Vb 0
- the current measured by the ammeter is given by the following equation (4). From this, if the sensor impedance ZS is obtained, the impedance of the sensor element can be measured without being affected by the current limiting resistance.
- the second method relates to a circuit system that realizes current limiting in the event of an accident without using a somewhat large resistor such as a current limiting resistor, as shown in Fig.5.
- a blocking capacitor for maintaining safety is provided between the sensor drive and the AC drive power supply for driving the measurement sensor having a frequency sufficiently higher than the commercial power supply of 50/60 Hz. Because the impedance of these capacitors is inversely proportional to the applied frequency, they have sufficient impedance to limit energy in the frequency band of 50/60 Hz or less for commercial power sources assumed at the time of an accident. At the time of measurement, the impedance can be realized so small that the influence on the measured value can be ignored due to the considerably high measurement drive frequency.
- Figure 5 circuit The current value measured by is given by Equation (5) according to Thevenin's theorem
- the sensor drive circuit configuration using the drive and feedback operational amplifiers takes advantage of the means for ignoring the impedance of the current limiting resistor, and the fact that the impedance of the blocking capacitor can be ignored when used in the high frequency band.
- a circuit of intrinsically safe explosion-proof structure in sensor signal processing is realized and the problem is solved.
- V in of the voltage 7 a applied to the sensor 1 is buffered by the driving operational amplifier 10 and applied to the sensor 1.
- the feedback operational amplifier 20 measures the value of the current flowing through the sensor 1 by feeding it back.
- the impedance Z S of the sensor 1 is obtained from the applied voltage V in and the measured current I according to the equation (4).
- the physical quantity of the object to be measured can be obtained by performing various calculations on ZS.
- the driving and feedback operational amplifier circuits are equipped with four current limiting resistors R h in series (through the terminals A and B from the sensor) on all lines connected to sensor 1. Assuming that all components except the current limiting resistor are broken, for example, each current limiting resistor R h If 250V is applied to all of them, it is assumed that the condition for safety is to limit the total current flowing from the four Rhs to the ground FG through the sensor to 10 mA or less. In that case, the design should be made so that the current from each Rh is limited to 2.5mA with each of the four Rhs being 100 ⁇ or more.
- the current given to the sensor 1 during normal measurement by the effect of the blocking capacitor Ch is given by the following equation (2). It is measured as shown in 6), and when commercial power is simply applied to Vin, the current is limited to a small value as in equation (5).
- the blocking capacitor Ch has a multi-stage configuration of at least two stages due to the requirement of intrinsic safety.
- R h is added for current limiting and DC bias. In the event of an accident, for example, when 250 V is applied to each current limiting resistor R h and each blocking capacitor, it is necessary for safety maintenance to limit the total current flowing from these to the ground FG through the sensor to 10 mA.
- each of the two Rh should be 100 ⁇ or more, the path current should be limited to 2.5 mA or less, and the capacitance of at least one surviving path should be 2 f'Ch (where f is the commercial frequency of 60 Hz).
- the value of Ch should be designed to be about 26nF or less to limit the current obtained by the product of 250V and 250V to 2.5mA or less.
- the effect of the blocking capacitor Ch can be ignored at measurement regardless of the frequency ⁇ by using an operational amplifier. It is.
- the measured current value is given by the following equation (7) (based on the principles shown in the above equations (2) and (3)). Also in this case, the two operational amplifiers 10 and 20 in the figure are assumed to be ideal.
- the driving and feedback operational amplifier circuits 10 and 20 are connected to sensor 1. All lines must be equipped with current limiting resistors or blocking capacitors. If all components except the current limiting resistor or the blocking capacitor are broken in the event of an accident, for example, if 250V is applied to all the paths of each current limiting resistor R h and Ch, the current path is 8 The values are determined as described above. R h should be designed to be 200 ⁇ or more, and Ch should be designed to be about 13nF or less.
- the current value is measured by an ammeter.
- the current measurement is not practical in terms of mounting an electric circuit, and voltage measurement is desirable.
- simply measuring this with the output of the feedback operational amplifier 20 in FIG. 4 depends on the accuracy of the current limiting resistor R h as in the following equation (8), which is inconvenient.
- V -— -Vin ⁇ ' ⁇ (8)
- the output voltage of the operational amplifier 20 can be expressed by the following equation (9). It is possible to obtain the sensor impedance ZS with high accuracy by dividing the voltage measurement result by Vin and ZREF, etc., without obtaining such Rh.
- the reference resistance ZREF is an element that is not related to explosion protection and has a value similar to that of the sensor (also common to the invention according to claim 5 below). It is also possible to configure with holding. (5) Embodiment of the invention according to claim 5
- the embodiment according to claim 3 (FIG. 6) is also unrealistic because it measures current.
- the output of the operational amplifier is to be measured as it is, from the calculation of the negative feedback voltage amplification of the operational amplifier consisting of the impedance due to R h and Ch and the impedance Zs of the sensor element, the measured voltage is expressed by the above equation (7). Is the product of the negative feedback impedance of the operational amplifier and the following equation (10).
- V — ⁇ Vin-(10)
- the sensor impedance ZS cannot be obtained with high accuracy because it includes the blocking capacitor and the limiting resistor Rh. Therefore, as an improvement of the invention according to claim 3, by configuring the circuit shown in FIG. 8, the output voltage of the operational amplifier 20 can be obtained by the equation (11) using the reference resistor 100 (ZREF). Therefore, the sensor impedance can be obtained with high accuracy.
- v _ ⁇ L. Vin ... (H)
- the current limiting resistor R h and the blocking capacitor Ch are all provided between the terminals of the operational amplifiers 10 and 20 and the sensor 1 and are intrinsically safe. The function is secured.
- the current paths are assumed to be 10 and the values of R h and Ch are determined as described above.
- R h should be designed to be 250 ⁇ or more and C h should be designed to be about 10nF or less.
- Fig. 2 shows an overall configuration diagram of instrumentation equipment in which a sensor element is placed in a hazardous location and an instrument body including a safety circuit is placed in a flameproof structure case in the hazardous location.
- Fig. 3 shows an example of an intrinsically safe explosion-proof circuit using only a current limiting resistor Rh, which is a conventional example.
- Non-hazardous locations shown in the figure include the explosion-proof structure case in the hazardous location. The same applies to the following figures.
- FIG. 4 shows an example of a current measuring circuit system using a current limiting resistor R h and an operational amplifier according to the first embodiment.
- FIG. 5 shows an example of a blocking capacitor circuit configuration according to the second aspect of the present invention.
- FIG. 6 is a circuit configuration including a blocking capacitor and an operational amplifier according to the invention of claim 3, showing an example of a current measurement type circuit.
- FIG. 7 is an improved circuit configuration according to claim 1 which is the invention according to claim 4, and shows an example of a voltage measurement type circuit.
- FIG. 8 is an improved circuit configuration according to claim 3, which is the invention according to claim 5, and shows an example of a voltage measurement type circuit.
- an operational amplifier circuit for driving and feedback is configured to measure the impedance of the sensor
- the invention which can accurately measure the impedance of the sensor by the action of a blocking capacitor having the function described above, and the invention of a negative feedback circuit configuration using a reference resistor for voltage detection, has a small space and cost.
- a sensor signal processing circuit with a simple intrinsically safe explosion-proof structure can be constructed. Since the safety holding circuit according to these inventions is realized by a small circuit, it can be easily installed in a non-dangerous place or a dangerous place, but also in a case of a flameproof structure. As a result, the user of this instrument can easily install an explosion-proof instrument as well as a non-explosion-proof instrument without requiring any special external equipment.
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- Arrangements For Transmission Of Measured Signals (AREA)
- Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)
- Investigating Or Analyzing Materials By The Use Of Fluid Adsorption Or Reactions (AREA)
- Air Bags (AREA)
- Measurement Of Current Or Voltage (AREA)
- Control Of Combustion (AREA)
- Testing Or Calibration Of Command Recording Devices (AREA)
Description
Claims
Priority Applications (6)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2003511208A JP3823272B2 (ja) | 2001-07-04 | 2001-07-04 | 本質安全防爆型センサ回路 |
PCT/JP2001/005835 WO2003005319A1 (en) | 2001-07-04 | 2001-07-04 | Intrinsically safe explosion-proof sensor circuit |
AT01947842T ATE313136T1 (de) | 2001-07-04 | 2001-07-04 | Intrinsisch sichere explosionssichere sensorschaltung |
US10/069,547 US6822431B2 (en) | 2001-07-04 | 2001-07-04 | Intrinsically safe sensor signal processing circuit |
DE60115963.2T DE60115963T3 (de) | 2001-07-04 | 2001-07-04 | Intrinsisch sichere explosionssichere sensorschaltung |
EP01947842.9A EP1403832B2 (en) | 2001-07-04 | 2001-07-04 | Intrinsically safe explosion-proof sensor circuit |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
PCT/JP2001/005835 WO2003005319A1 (en) | 2001-07-04 | 2001-07-04 | Intrinsically safe explosion-proof sensor circuit |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2003005319A1 true WO2003005319A1 (en) | 2003-01-16 |
Family
ID=11737518
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/JP2001/005835 WO2003005319A1 (en) | 2001-07-04 | 2001-07-04 | Intrinsically safe explosion-proof sensor circuit |
Country Status (6)
Country | Link |
---|---|
US (1) | US6822431B2 (ja) |
EP (1) | EP1403832B2 (ja) |
JP (1) | JP3823272B2 (ja) |
AT (1) | ATE313136T1 (ja) |
DE (1) | DE60115963T3 (ja) |
WO (1) | WO2003005319A1 (ja) |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2007152020A (ja) * | 2005-12-08 | 2007-06-21 | Olympus Corp | 内視鏡装置 |
JP2012008598A (ja) * | 2011-09-12 | 2012-01-12 | Olympus Corp | 内視鏡装置 |
US8279273B2 (en) | 2006-01-27 | 2012-10-02 | Olympus Corporation | Endoscope apparatus |
CN105842543A (zh) * | 2016-05-12 | 2016-08-10 | 天地(常州)自动化股份有限公司 | 本质安全型接地电阻测量系统 |
Families Citing this family (15)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE10356985A1 (de) * | 2003-12-05 | 2005-07-07 | Cooper Crouse-Hinds Gmbh | Datenübertragungseinrichtung |
US7057577B1 (en) * | 2004-05-13 | 2006-06-06 | Ventek Llc | Antenna connector for hazardous area |
US7271679B2 (en) * | 2005-06-30 | 2007-09-18 | Intermec Ip Corp. | Apparatus and method to facilitate wireless communications of automatic data collection devices in potentially hazardous environments |
DE102005062422A1 (de) | 2005-12-27 | 2007-07-05 | Vega Grieshaber Kg | Schaltkreis-Anordnung mit Exschutz |
DE102008029956A1 (de) | 2008-06-26 | 2009-12-31 | Endress + Hauser Flowtec Ag | Meßsystem mit einem Sensormodul und einem Transmittermodul |
DE102008053920A1 (de) | 2008-10-30 | 2010-05-06 | Endress + Hauser Conducta Gesellschaft für Mess- und Regeltechnik mbH + Co. KG | Verteilermodul bzw. damit gebildetes Messsystem |
WO2012021681A2 (en) * | 2010-08-11 | 2012-02-16 | Siemens Industry, Inc. | Intrinsically safe thermal conductivity detector for process gas chromatograph |
WO2012115967A1 (en) | 2011-02-21 | 2012-08-30 | Zih Corp. | Isolation devices that pass coupler output signals |
US9518968B2 (en) | 2013-05-17 | 2016-12-13 | Rosemount Analytical Inc. | In situ heated oxygen probe with intrinsically safe output |
US10962622B2 (en) * | 2013-12-23 | 2021-03-30 | Rosemount Inc. | Analog process variable transmitter with electronic calibration |
US9778149B2 (en) | 2014-05-02 | 2017-10-03 | Swagelok Company | Fluid sample system and method |
US10480765B2 (en) | 2015-06-08 | 2019-11-19 | Eaton Intelligent Power Limited | Integration of sensor components with light fixtures in hazardous environments |
DE102018120878A1 (de) * | 2018-08-27 | 2020-02-27 | Endress+Hauser Conducta Gmbh+Co. Kg | Sensor und Sensoranordnung |
CN113348341B (zh) * | 2018-12-20 | 2023-09-01 | 罗斯蒙特储罐雷达股份公司 | 具有防爆壳体和浮置屏障的导波雷达物位计 |
CN114051340B (zh) * | 2021-11-18 | 2023-10-13 | 张家港氢芯电气系统科技有限公司 | 基于模块化设计的氢气加注控制器 |
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JPS55112699A (en) * | 1979-02-20 | 1980-08-30 | Mitsubishi Electric Corp | Rotary body signal transmission device |
JPS5816073Y2 (ja) * | 1976-12-28 | 1983-04-01 | 横河電機株式会社 | 抵抗・電気信号変換装置 |
JPS6220077Y2 (ja) * | 1979-06-04 | 1987-05-22 | ||
JPH0657042U (ja) * | 1992-10-28 | 1994-08-05 | 株式会社中村電機製作所 | 安全保持装置 |
Family Cites Families (5)
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US3611127A (en) * | 1968-09-16 | 1971-10-05 | Robert E Vosteen | Electrostatic potential and field measurement apparatus having a capacitor detector with feedback to drive the capacitor detector to the potential being measured |
US3845356A (en) * | 1972-04-06 | 1974-10-29 | Foxboro Co | Process control system for hazardous areas |
US3997733A (en) * | 1975-05-01 | 1976-12-14 | Browne-Davies Electronic Corporation | Intrinsically safe communication systems |
US4812778A (en) * | 1988-01-25 | 1989-03-14 | Electro-Mechanics, Inc. | Isolation amplifier |
EP1080458B1 (en) * | 1998-05-21 | 2007-08-15 | Smiths Aerospace, Inc. | Fault condition protective device for aircraft fuel gauging systems |
-
2001
- 2001-07-04 EP EP01947842.9A patent/EP1403832B2/en not_active Expired - Lifetime
- 2001-07-04 DE DE60115963.2T patent/DE60115963T3/de not_active Expired - Lifetime
- 2001-07-04 US US10/069,547 patent/US6822431B2/en not_active Expired - Lifetime
- 2001-07-04 AT AT01947842T patent/ATE313136T1/de not_active IP Right Cessation
- 2001-07-04 JP JP2003511208A patent/JP3823272B2/ja not_active Expired - Lifetime
- 2001-07-04 WO PCT/JP2001/005835 patent/WO2003005319A1/ja active IP Right Grant
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
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JPS5816073Y2 (ja) * | 1976-12-28 | 1983-04-01 | 横河電機株式会社 | 抵抗・電気信号変換装置 |
JPS55112699A (en) * | 1979-02-20 | 1980-08-30 | Mitsubishi Electric Corp | Rotary body signal transmission device |
JPS6220077Y2 (ja) * | 1979-06-04 | 1987-05-22 | ||
JPH0657042U (ja) * | 1992-10-28 | 1994-08-05 | 株式会社中村電機製作所 | 安全保持装置 |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2007152020A (ja) * | 2005-12-08 | 2007-06-21 | Olympus Corp | 内視鏡装置 |
US8194380B2 (en) | 2005-12-08 | 2012-06-05 | Olympus Corporation | Endoscope apparatus |
US8279273B2 (en) | 2006-01-27 | 2012-10-02 | Olympus Corporation | Endoscope apparatus |
JP2012008598A (ja) * | 2011-09-12 | 2012-01-12 | Olympus Corp | 内視鏡装置 |
CN105842543A (zh) * | 2016-05-12 | 2016-08-10 | 天地(常州)自动化股份有限公司 | 本质安全型接地电阻测量系统 |
Also Published As
Publication number | Publication date |
---|---|
JP3823272B2 (ja) | 2006-09-20 |
DE60115963D1 (de) | 2006-01-19 |
EP1403832B2 (en) | 2016-06-01 |
DE60115963T2 (de) | 2006-06-29 |
JPWO2003005319A1 (ja) | 2004-10-28 |
EP1403832A1 (en) | 2004-03-31 |
ATE313136T1 (de) | 2005-12-15 |
EP1403832A4 (en) | 2004-07-28 |
US6822431B2 (en) | 2004-11-23 |
DE60115963T3 (de) | 2016-09-29 |
EP1403832B1 (en) | 2005-12-14 |
US20040113635A1 (en) | 2004-06-17 |
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