2-wire transmitter

Abstract

To provide a two-channel transmitter with improved technology for lighting LEDs.SOLUTION: A two-channel transmitter 10 according to the present disclosure includes: a measurement circuit 11; a current output circuit 12 connected in parallel with the measurement circuit 11; an LED 15 connected in parallel with the measurement circuit 11 and the current output circuit 12; and a switch 13 that allows switching of whether current is applied to the LED 15. The measurement circuit 11 is equipped with a control unit 112. The control unit 112 turns off the switch 13 during normal operation and turns on the switch 13 when an error occurs.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a two-wire transmitter. [Background technology]

[0002] Conventionally, two-wire transmitters have been used in plants, factories, etc. Two-wire transmitters can measure various physical quantities such as flow rate, pressure, temperature, etc.

[0003] A two-wire transmitter may have a display such as an LCD (Liquid Crystal Display), etc. If the two-wire transmitter has such a display, it can notify the user that an error has occurred by, for example, displaying an error symbol when an error occurs.

[0004] However, even if an error symbol is displayed on the LCD, it is difficult to notice the error symbol due to poor visibility when the two-wire transmitter is installed in a dark location.

[0005] One way to make errors more noticeable when they occur is to light up an LED (Light Emitting Diode). However, because the measurement circuitry in two-wire transmitters typically needs to operate at a current of approximately 3.5 mA or less, it is not possible to provide an LED in the measurement circuit and have it light up.

[0006] As a two-wire transmitter capable of lighting an LED, for example, Patent Document 1 discloses a two-wire transmitter equipped with a battery for lighting the LED, and Patent Document 2 discloses a configuration in which a Zener diode is connected in series with the two-wire transmitter to ensure the voltage required to light the LED. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-24067 [Patent Document 2] Japanese Patent Application Publication No. 5-225484 Summary of the Invention [Problem to be solved by the invention]

[0008] The two-wire transmitter disclosed in Patent Document 1 is equipped with a battery inside the device to light the LED. With a configuration in which a battery is equipped inside the device in this way, the battery can cause electric sparks, and the device does not meet the requirements for an intrinsically safe explosion-proof structure.

[0009] The two-wire transmitter disclosed in Patent Document 2 has a Zener diode connected in series with the two-wire transmitter. With this configuration, the voltage drops by about 1.5 V in the Zener diode, which increases the minimum operating voltage of the voltage source that supplies voltage to the two-wire transmitter.

[0010] As such, there was room for improvement in two-wire transmitters capable of lighting LEDs.

[0011] Therefore, an object of the present disclosure is to provide a two-wire transmitter with improved technology for lighting an LED. [Means for solving the problem]

[0012] A two-wire transmitter according to some embodiments includes a measurement circuit, a current output circuit connected in parallel with the measurement circuit, an LED connected in parallel with the measurement circuit and the current output circuit, and a switch for switching whether or not a current flows through the LED, the measurement circuit including a control unit that turns off the switch during normal operation and turns on the switch when an error occurs. Such a two-wire transmitter can improve the technology for lighting the LED.

[0013] In one embodiment of the two-wire transmitter, the control unit may control the current flowing through the current output circuit when the error occurs so that the two-wire transmitter outputs a burn-up signal, thereby notifying the receiving instrument that an error has occurred.

[0014] In one embodiment, the measurement circuit may further include a sensor, and the control unit may control a current flowing through the current output circuit so that the two-wire transmitter outputs a current corresponding to a physical quantity measured by the sensor during the normal operation. This allows information about the physical quantity measured by the sensor to be transmitted to a receiving instrument.

[0015] In one embodiment of the two-wire transmitter, the control unit may turn off the switch when the error that occurred at the time the error occurred is resolved, thereby allowing the transmitter to return to normal operation after the error is resolved.

[0016] The two-wire transmitter according to one embodiment may further include a resistor connected in series with the LED, thereby limiting the current flowing through the LED.

[0017] In one embodiment of the two-wire transmitter, the measurement circuit may further include a display unit, and the control unit may turn on a backlight of the display unit when the error occurs, thereby making it possible to notify the user of the error by turning on the backlight of the display unit.

[0018] In one embodiment of the two-wire transmitter, the control unit controls the current flowing through the current output circuit so that the two-wire transmitter outputs a burn-down signal when the error occurs, and turns off the switch when the error occurs if the burn-down signal is output. This makes it possible to notify the occurrence of an error by the burn-down signal. [Effects of the Invention]

[0019] According to the present disclosure, it is possible to provide a two-wire transmitter with improved technology for lighting an LED. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of a two-wire transmitter according to an embodiment. [Figure 2] FIG. 4 is a diagram illustrating an operation during normal operation of a two-wire transmitter according to an embodiment. [Figure 3] FIG. 10 is a diagram illustrating an operation of a two-wire transmitter according to an embodiment when an error occurs. DETAILED DESCRIPTION OF THE INVENTION

[0021] 1 is a diagram showing a schematic configuration of a two-wire transmitter 10 according to an embodiment. The configuration and functions of the two-wire transmitter 10 according to an embodiment will be described with reference to FIG.

[0022] The two-wire transmitter 10 is connected to a DC voltage source 1 and a receiving instrument 2 via two transmission lines.

[0023] DC voltage source 1 supplies a DC voltage to two-wire transmitter 10. DC voltage source 1 may be a DC voltage source capable of supplying a DC voltage of, for example, about 10 to 40V.

[0024] Two-wire transmitter 10 operates using a DC voltage supplied from DC voltage source 1. Two-wire transmitter 10 measures a physical quantity and outputs a current corresponding to the measured physical quantity as a transmission signal. Typically, the transmission signal output by two-wire transmitter 10 is 4 to 20 mA.

[0025] The receiving instrument 2 receives the transmission signal output by the two-wire transmitter 10 .

[0026] The two-wire transmitter 10 includes a measurement circuit 11, a current output circuit 12, a switch 13, a resistor 14, and an LED 15.

[0027] The measurement circuit 11 includes a sensor 111 , a control unit 112 , a display unit 113 , a storage unit 114 , and an input unit 115 .

[0028] The sensor 111 is a sensor that measures a physical quantity, such as a flow rate, a pressure, or a temperature.

[0029] The control unit 112 includes at least one processor, at least one dedicated circuit, or a combination thereof. The processor is a general-purpose processor such as a CPU (Central Processing Unit), or a dedicated processor specialized for a specific process.

[0030] During normal operation, the control unit 112 controls the current flowing through the current output circuit 12 so that the two-wire transmitter 10 outputs a current corresponding to the physical quantity measured by the sensor 111 as a transmission signal.

[0031] Control unit 112 controls the on / off of switch 13. When control unit 112 turns on switch 13, current flows through LED 15, causing LED 15 to light up. When control unit 112 turns off switch 13, no current flows through LED 15, causing LED 15 to not light up.

[0032] The display unit 113 includes one or more output interfaces for displaying information, and may include, for example, an LCD (Liquid Crystal Display) or an organic EL (Electro Luminescent) display.

[0033] The storage unit 114 may be, for example, but is not limited to, a semiconductor memory, a magnetic memory, or an optical memory. The storage unit 114 stores any information used in the operation of the two-wire transmitter 10. For example, the storage unit 114 may store system programs, application programs, various data, and the like.

[0034] The input unit 115 includes one or more input interfaces that acquire input information based on a user's operation. For example, the input unit 115 may include a button or the like.

[0035] The current output circuit 12 is connected in parallel with the measurement circuit 11. The current output circuit 12 can output a variable current in accordance with the control of the control unit 112. The current output circuit 12 may be, for example, an NPN transistor. Fig. 1 shows a case where the current output circuit 12 is an NPN transistor.

[0036] The switch 13 is a switch that can switch whether or not a current flows through the LED 15. The on / off of the switch 13 is controlled by the control unit 112. The switch 13 may be a switch of any configuration that can be turned on / off by an electric signal.

[0037] When the control unit 112 turns on the switch 13, a current flows through the LED 15, causing the LED 15 to light up. When the control unit 112 turns off the switch 13, no current flows through the LED 15, causing the LED 15 to not light up.

[0038] The resistor 14 is connected in series with the LED 15. The resistor 14 limits the current flowing through the LED 15.

[0039] The LED 15 is connected in parallel to the measurement circuit 11 and the current output circuit 12. The LED 15 may be any LED that can be turned on by passing a current through it. Although one LED 15 is shown in Fig. 1, a configuration in which multiple LEDs 15 are connected in series may also be used.

[0040] The LED 15 may be installed in a highly visible location, such as on the housing of the two-wire transmitter 10. The LED 15 can notify the operator that an error has occurred by lighting up.

[0041] (during normal operation) Referring to FIG. 2, the operation of the two-wire transmitter 10 according to the embodiment during normal operation will be described.

[0042] During normal operation, the two-wire transmitter 10 outputs, as a current signal, a current corresponding to the physical quantity measured by the sensor 111. In this embodiment, the two-wire transmitter 10 is described as outputting a current of 4 to 20 mA as the transmission signal. In addition, in this embodiment, the description is given assuming that a current of 3.5 mA steadily flows through the measurement circuit 11.

[0043] The control unit 112 turns off the switch 13 during normal operation. Therefore, during normal operation, no current flows through the LED 15, and therefore the LED 15 does not light up. In other words, the state in which the LED 15 is not lit is the state in which the two-wire transmitter 10 is operating normally. By visually confirming that the LED 15 is not lit, the operator can determine that the two-wire transmitter 10 is operating normally.

[0044] The control unit 112 controls the current flowing through the current output circuit 12 so that the two-wire transmitter 10 outputs a current corresponding to the physical quantity measured by the sensor 111 .

[0045] More specifically, the control unit 112 controls the current output circuit 12 so that a current of 0.5 to 16.5 mA flows through the current output circuit 12 in accordance with the physical quantity measured by the sensor 111. In this case, since a current of 3.5 mA flows through the measurement circuit 11, the two-wire transmitter 10 outputs a current of 4 to 20 mA as a transmission signal.

[0046] (When an error occurs) With reference to FIG. 3, the operation of the two-wire transmitter 10 according to one embodiment when an error occurs will be described.

[0047] When an error occurs, the two-wire transmitter 10 outputs a burn-up signal. The burn-up signal is a signal indicating that an error has occurred, and corresponds to the flow of a current greater than the normal transmission signal of 4 to 20 mA. In this embodiment, the two-wire transmitter 10 is described as outputting a current of 22 mA as the burn-up signal. Furthermore, in this embodiment, the description is given assuming that when the switch 13 is turned on, a current of 18 mA flows through the LED 15.

[0048] When an error occurs, the control unit 112 turns on the switch 13. As a result, when an error occurs, a current flows through the LED 15, and the LED 15 lights up. By visually confirming that the LED 15 is lit, the operator can easily understand that an error has occurred, even if the two-wire transmitter 10 is installed in a dark place.

[0049] The control unit 112 controls the current flowing through the current output circuit 12 so that the two-wire transmitter 10 outputs a current of 22 mA as a burn-up signal.

[0050] More specifically, the control unit 112 controls the current output circuit 12 so that a current of 0.5 mA flows through the current output circuit 12. At this time, a current of 3.5 mA flows through the measurement circuit 11, and a current of 18 mA flows through the LED 15, so the two-wire transmitter 10 outputs a current of 22 mA as a burn-up signal.

[0051] When the error that has occurred is resolved, the control unit 112 turns off the switch 13 and transitions to normal operation.

[0052] (burndown signal) The two-wire transmitter 10 may be capable of outputting a burn-down signal instead of a burn-up signal when an error occurs. The burn-down signal indicates that an error has occurred, and corresponds to a current smaller than the normal transmission signal of 4 to 20 mA. The burn-down signal may be, for example, a current of 3.6 mA.

[0053] The control unit 112 selects whether to output a burn-up signal or a burn-down current when an error occurs, in response to an input operation received by the input unit 115 from an operator.

[0054] When a burn-down signal is to be output when an error occurs, the control unit 112 turns off the switch 13 when an error occurs. The control unit 112 also controls the current flowing through the current output circuit 12 so that the two-wire transmitter 10 outputs a current of 3.6 mA as the burn-down signal.

[0055] More specifically, the control unit 112 controls the current output circuit 12 so that a current of 0.1 mA flows through the current output circuit 12. At this time, since a current of 3.5 mA flows through the measurement circuit 11, the two-wire transmitter 10 outputs a current of 3.6 mA as the burn-down signal.

[0056] The two-wire transmitter 10 according to the embodiment described above can improve the technology for lighting the LED 15. More specifically, the two-wire transmitter 10 according to the embodiment includes a current output circuit 12 connected in parallel with the measurement circuit 11, an LED 15 connected in parallel with the measurement circuit 11 and the current output circuit 12, and a switch 13 that can switch whether or not current flows through the LED 15. The control unit 112 turns the switch 13 off during normal operation and turns the switch 13 on when an error occurs. Thus, the two-wire transmitter 10 according to the embodiment does not include a battery. Because batteries can cause electric sparks, including a battery does not satisfy the requirements for an intrinsically safe explosion-proof structure. However, the two-wire transmitter 10 according to the embodiment can light the LED 15 even without a battery, thereby satisfying the requirements for an intrinsically safe explosion-proof structure. Furthermore, in the two-wire transmitter 10 according to the embodiment, the LED 15 is connected in parallel with the measurement circuit 11. Therefore, the minimum operating voltage of the DC voltage source 1 can be kept low. In this way, the two-wire transmitter 10 according to one embodiment can improve the technique for lighting the LED 15.

[0057] It will be apparent to those skilled in the art that the present disclosure can be embodied in other specific forms other than the above-described embodiments without departing from the spirit or essential characteristics thereof. Therefore, the foregoing description is illustrative and not limiting. The scope of the disclosure is defined not by the foregoing description but by the appended claims. All modifications within the range of equivalents of any modifications are intended to be encompassed therein.

[0058] For example, the arrangement and number of each component described above are not limited to the above description and the illustrations in the drawings, and may be arbitrarily configured as long as the functions thereof can be realized.

[0059] For example, in the above-described embodiment, the operation of turning on the LED 15 when an error occurs has been described, but the two-wire transmitter 10 may turn on the backlight of the display unit 113 to notify that an error has occurred. In this case, when an error occurs, the control unit 112 may leave the switch 13 off and pass a current through the backlight of the display unit 113 to turn on the backlight of the display unit 113.

[0060] For example, in the above embodiment, the LED 15 is turned on when an error occurs. However, the two-wire transmitter 10 may blink the LED 15 when an error occurs.

[0061] For example, in the above-described embodiment, the current output circuit 12 is an NPN transistor, but the current output circuit 12 may be a circuit of any configuration as long as it can output a variable current. [Explanation of symbols]

[0062] 1 DC voltage source 2 Receiving instrument 10 Two-wire transmitter 11 Measurement circuit 12 Current output circuit 13 Switch 14 Resistance 15 LED 111 Sensor 112 Control Unit 113 Display section 114 Storage section 115 Input section

Claims

1. A measurement circuit; a current output circuit connected in parallel with the measurement circuit; an LED connected in parallel to the measurement circuit and the current output circuit; a switch capable of switching whether or not a current flows through the LED; Equipped with the measurement circuit includes a control unit; The control unit turns the switch off during normal operation and turns the switch on when an error occurs.

2. 2. The two-wire transmitter according to claim 1, The control unit controls the current flowing through the current output circuit when the error occurs so that the two-wire transmitter outputs a burn-up signal.

3. 2. The two-wire transmitter according to claim 1, the measurement circuit further comprises a sensor; The control unit controls the current flowing through the current output circuit so that the two-wire transmitter outputs a current corresponding to the physical quantity measured by the sensor during the normal operation.

4. 2. The two-wire transmitter according to claim 1, The control unit turns off the switch when the error that occurred at the time the error occurred is resolved.

5. 2. The two-wire transmitter according to claim 1, The two-wire transmitter further comprises a resistor connected in series with the LED.

6. 2. The two-wire transmitter according to claim 1, The measurement circuit further includes a display unit, The control unit turns on a backlight of the display unit when the error occurs.

7. 2. The two-wire transmitter according to claim 1, The control unit When the error occurs, the current flowing through the current output circuit can be controlled so that the two-wire transmitter outputs a burn-down signal; A two-wire transmitter that, when outputting the burn-down signal, turns off the switch when the error occurs.

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