Two-wire system conveyor

Abstract

The two-wire transmitter 10 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 capable of switching whether to apply a current to the LED 15. The measurement circuit 11 comprises a controller 112. The controller 112 turns off the switch 13 during normal operation and turns on the switch 13 when an error occurs.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and the benefit of Japanese Patent Application No. 2023-045957, filed on March 22, 2023, which is hereby incorporated by reference herein in its entirety. Technical Field

[0003] The present disclosure relates to a two-wire transmitter. Background Art

[0004] Conventionally, two-wire transmitters (2-wire transmitters, two-wire transmitters) are used in plants and factories, etc. The two-wire transmitters can measure various physical quantities, such as flow, pressure, temperature, etc.

[0005] The two-wire transmitter may include a display, such as a liquid crystal display (LCD). By having such a display, the two-wire transmitter is able to report that an error has occurred, for example by displaying an error symbol when an error occurs.

[0006] However, even when the error symbol is displayed on the LCD, it may be difficult to notice the error symbol due to poor visibility, such as when the two-wire transmitter is installed in a dark place.

[0007] One way to more easily notice an error when it occurs is to turn on a light emitting diode (LED). However, the measurement circuit included in the two-wire transmitter must operate normally at a current of 3.5 mA or less, so including an LED in the measurement circuit and lighting it is not possible.

[0008] As a two-wire transmitter capable of lighting an LED, for example, Patent Literature (PTL) 1 describes a two-wire transmitter including a battery for lighting an LED. In addition, PTL 2 describes a configuration in which a Zener diode is connected in series with the two-wire transmitter to ensure a voltage required to light an LED.

[0009] Citation List:

[0010] Patent Literature

[0011] PTL1: JP2006-024067A

[0012] PTL2:JP H05-225484A Summary of the Invention

[0013] (Technical Issues)

[0014] The two-wire transmitter described in PTL 1 includes a battery inside the device to light up the LED. This configuration including a battery inside the device cannot satisfy the requirement for a safety explosion-proof structure in nature because the battery can be a source of electric sparks.

[0015] The two-wire transmitter described in PTL 2 includes a Zener diode connected in series with the two-wire transmitter. With this configuration, the voltage drop at the Zener diode is about 1.5 V, resulting in a higher minimum operating voltage of the voltage source that supplies voltage to the two-wire transmitter.

[0016] Therefore, there is room for improvement in the two-wire transmitter capable of lighting up the LED.

[0017] Therefore, it would be helpful to provide a two-wire transmitter having improved technology for lighting up the LED.

[0018] (Solution to the problem)

[0019] The two-wire transmitter according to at least one embodiment 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 capable of switching whether to apply current to the LED, wherein the measurement circuit includes a controller that turns off the switch during normal operation and turns on the switch when an error occurs. According to this two-wire transmitter, the technology for lighting up the LED is improved.

[0020] In the two-wire transmitter according to the embodiment, the controller controls the current flowing through the current output circuit so that the two-wire transmitter outputs a fuel consumption signal when an error occurs. This allows the receiver to be notified that an error has occurred.

[0021] In the two-wire transmitter according to the embodiment, the measurement circuit further includes a sensor, and during normal operation, the controller controls the 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. This allows information about the physical quantity measured by the sensor to be transmitted to the receiver.

[0022] In the two-wire transmitter according to the embodiment, when the error that has occurred when an error occurs has been resolved, the controller turns off the switch. This allows a return to normal operation after the error is resolved.

[0023] The two-wire transmitter according to the embodiment further includes a resistor connected in series with the LED.

[0024] This limits the current flowing to the LED.

[0025] In the two-wire transmitter according to the embodiment, the measurement circuit further includes a display, and the controller turns on a backlight of the display when the error occurs. This allows the error to be reported by turning on the backlight of the display.

[0026] In the two-wire transmitter according to the embodiment, the controller is capable of controlling the current flowing through the current output circuit such that the two-wire transmitter outputs a burnout signal when the error occurs; and

[0027] When the burnout signal is output, the controller turns off the switch when the error occurs. This allows the error to have occurred to be reported by the burnout signal.

[0028] (Beneficial Effects)

[0029] The present disclosure provides a two-wire transmitter having improved technology for lighting an LED. BRIEF DESCRIPTION OF DRAWINGS

[0030] In the drawings:

[0031] Figure 1 is a view showing a schematic structure of a two-wire transmitter according to one embodiment;

[0032] Figure 2 normal operation of a two-wire transmitter according to one embodiment; and

[0033] Figure 3 operation of a two-wire transmitter according to one embodiment when an error occurs. DETAILED DESCRIPTION

[0034] Figure 1 is a view showing a schematic structure of a two-wire transmitter 10 according to one embodiment. The structure and functions of the two-wire transmitter 10 according to this embodiment are described with reference to Figure 1

[0035] The two-wire transmitter 10 is connected to a direct current (DC) voltage source 1 and a receiver 2 via two transmission lines.

[0036] The DC voltage source 1 supplies a DC voltage to the two-wire transmitter 10. The DC voltage source 1 can be, for example, a DC voltage source capable of supplying a DC voltage of 10 V to 40 V.

[0037] The two-wire transmitter 10 operates by means of the DC voltage supplied from the DC voltage source 1. The 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 the two-wire transmitter 10 is 4 mA to 20 mA.

[0038] The receiver 2 receives the transmission signal output by the two-wire transmitter 10. ​

[0039] 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.

[0040] The measurement circuit 11 includes a sensor 111, a controller 112, a display 113, a memory 114, and an input 115.

[0041] The sensor 111 is a sensor that measures a physical quantity. The physical quantity measured by the sensor 111 can be, for example, flow rate, pressure, temperature, or the like.

[0042] The controller 112 includes at least one processor, at least one dedicated circuit, or a combination of at least one processor and at least one dedicated circuit. Each processor is a general-purpose processor, for example, a central processing unit (CPU), or a dedicated processor specialized for a specific process.

[0043] The controller 112 controls the current flowing through the current output circuit 12 so that, during normal operation, the two-wire transmitter 10 outputs, as a transmission signal, a current corresponding to the physical quantity measured by the sensor 111.

[0044] The controller 112 controls the on / off state of the switch 13. When the controller 112 turns on the switch 13, the current flows to the LED 15, and thus the LED 15 lights up. When the controller 112 turns off the switch 13, no current flows to the LED 15, and thus the LED 15 does not light up.

[0045] The display 113 includes one or more output interfaces that display information. The display 113 can include, for example, a liquid crystal display (LCD) or an electroluminescent (EL) display.

[0046] The memory 114 includes, but is not limited to, a semiconductor memory, a magnetic memory, an optical memory, or the like. The memory 114 stores any information used in the operation of the two-wire transmitter 10. For example, the memory 114 can store a system program, an application program, various data, or the like.

[0047] The input 115 includes one or more input interfaces that obtain input information based on a user operation. For example, the input 115 can include a button or the like.

[0048] The current output circuit 12 is connected in parallel with the measurement circuit 11. The current output circuit 12 is capable of outputting a variable current in response to the control of the controller 112. The current output circuit 12 can be, for example, a negative-positive-negative (NPN) transistor. Figure 1 A case where the current output circuit 12 is an NPN transistor is shown.

[0049] The switch 13 is a switch that can switch whether or not to apply a current to the LED 15. The on / off state of the switch 13 is controlled by the controller 112. The switch 13 can be any configuration of a switch that can be turned on or off by an electric signal.

[0050] When the controller 112 turns on the switch 13, a current flows to the LED 15, so that the LED 15 lights up. When the controller 112 turns off the switch 13, no current flows to the LED 15, so that the LED 15 does not light up.

[0051] The resistor 14 is a resistor connected in series with the LED 15. The resistor 14 limits the current flowing to the LED 15.

[0052] The LED 15 is connected in parallel with the measurement circuit 11 and the current output circuit 12. The LED 15 can be any LED that can light up by a current flowing therethrough. In Figure 1 , one LED 15 is shown, but a plurality of LEDs 15 can be connected in series.

[0053] The LED 15 can be installed at a highly visible position, for example, on the housing of the two-wire transmitter 10, or the like. The LED 15 can light up to notify an operator that an error has occurred.

[0054] (normal operation)

[0055] Reference Figure 2 describes the normal operation of the two-wire transmitter 10 according to one embodiment.

[0056] In the normal operation, the two-wire transmitter 10 outputs a current corresponding to a physical quantity measured by the sensor 111 as a current signal. According to the present embodiment, the two-wire transmitter 10 outputs a current of 4 mA to 20 mA as a transmission signal. Further, according to the present embodiment, the measurement circuit 11 has a stable current of 3.5 mA.

[0057] The controller 112 turns off the switch 13 during the normal operation. Therefore, during the normal operation, no current flows to the LED 15, so that the LED 15 does not light up. In other words, during the normal operation, the LED 15 does not light up. By seeing that the LED 15 does not light up, the operator can determine that the two-wire transmitter 10 is operating normally.

[0058] The controller 112 controls the current flowing through the current output circuit 12 so that the two-wire transmitter 10 outputs a current corresponding to a physical quantity measured by the sensor 111.

[0059] More specifically, the controller 112 controls the current output circuit 12 in accordance with the physical quantity measured by the sensor 111 so that a current of 0.5 mA to 16.5 mA flows through the current output circuit 12. At this time, a current of 3.5 mA flows through the measurement circuit 11, and thus the two-wire transmitter 10 outputs a current of 4 mA to 20 mA as a transmission signal.

[0060] (When an error occurs)

[0061] Reference Figure 3 The operation of the two-wire transmitter 10 according to one embodiment when an error occurs is described.

[0062] When an error occurs, the two-wire transmitter 10 outputs a burnup signal. The burnup signal is a signal indicating that an error is occurring, and a current larger than the normal transmission signal of 4 mA to 20 mA corresponds to the burnup signal. According to the present embodiment, the two-wire transmitter 10 outputs a current of 22 mA as the burnup signal. Further, according to the present embodiment, a current of 18 mA flows through the LED 15 when the switch 13 is on.

[0063] The controller 112 turns on the switch 13 when an error occurs. Thus, when an error occurs, a current flows to the LED 15, and thus the LED 15 is lit. By seeing that the LED 15 is lit, an operator can easily determine that an error has occurred even when the two-wire transmitter 10 is installed in a dark place.

[0064] The controller 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 the burnup signal.

[0065] More specifically, the controller 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, and thus the two-wire transmitter 10 outputs a current of 22 mA as the burnup signal.

[0066] When the error that has occurred is resolved, the controller 112 turns off the switch 13 and shifts to normal operation.

[0067] (Burndown signal)

[0068] The two-wire transmitter 10 can output a burndown signal instead of the burnup signal when an error occurs. The burndown signal is a signal indicating that an error is occurring, and a current smaller than the normal transmission signal of 4 mA to 20 mA corresponds to the burndown signal. For example, the burndown signal can be a current of 3.6 mA.

[0069] The controller 112 selects whether to output a fuel consumption signal or a burnout signal when an error occurs, based on an input operation received from an operator via the input unit 115 .

[0070] When outputting a burnout signal when an error occurs, the controller 112 opens the switch 13 when an error occurs. In addition, the controller 112 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 burnout signal.

[0071] More specifically, the controller 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, a current of 3.5 mA is flowing through the measurement circuit 11, and therefore, the two-wire transmitter 10 outputs a current of 3.6 mA as a burnout signal.

[0072] According to the embodiment of the two-wire transmitter 10 described above, the technique for lighting the LED 15 is improved. More specifically, the two-wire transmitter 10 according to the embodiment includes a current output circuit 12 connected in parallel with a measurement circuit 11, an LED 15 connected in parallel with the measurement circuit 11 and the current output circuit 12, and a switch 13 capable of switching whether current is applied to the LED 15. Furthermore, a controller 112 opens the switch 13 during normal operation and closes it when an error occurs. Therefore, the two-wire transmitter 10 according to the embodiment does not include a battery. Batteries can cause sparks, so including a battery does not meet the requirements for an intrinsically safe and explosion-proof structure. However, the two-wire transmitter 10 according to the embodiment can illuminate the LED 15 even without a battery, thus meeting the requirements for an intrinsically safe and 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. Therefore, according to the embodiment of the two-wire transmitter 10, the technique of lighting the LED 15 is improved.

[0073] It will be apparent to those skilled in the art that the present disclosure may be implemented in a manner different from the above-described embodiments without departing from the spirit or essential features of the present disclosure. Therefore, the foregoing description is illustrative rather than restrictive. The scope of the present disclosure is defined by the appended claims rather than by the foregoing description. Any modifications falling within the scope of equivalents are intended to be included within the scope of the present disclosure.

[0074] For example, the arrangement and quantity of each component are not limited to those shown in the above description and drawings, and can be arbitrarily configured as long as the function can be achieved.

[0075] For example, according to the above embodiment, the operation of turning on the LED 15 at the time of error occurrence is described, but the two-wire transmitter 10 can turn on the backlight of the display 113 to report that the error has occurred. In this case, the controller 112 can make the switch 13 off and apply a current to the backlight of the display 113 to turn on the backlight of the display 113 at the time of error occurrence.

[0076] For example, according to the above embodiment, the operation of turning on the LED 15 at the time of error occurrence is described, but the two-wire transmitter 10 can make the LED 15 blink at the time of error occurrence.

[0077] For example, according to the above embodiment, the case where the current output circuit 12 is an NPN transistor is described, but the current output circuit 12 can be a circuit of any configuration as long as a variable output current is possible.

[0078] Reference symbol list

[0079] 1 DC voltage source

[0080] 2 Receiver

[0081] 10 Two-wire transmitter

[0082] 11 Measurement circuit

[0083] 12 Current output circuit

[0084] 13 Switch

[0085] 14 Resistor

[0086] 15 LED

[0087] 111 Sensor

[0088] 112 Controller

[0089] 113 Display

[0090] 114 Memory

[0091] 115 Input

Claims

1. A two-wire transmitter comprising: 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 capable of switching whether or not to apply a current to the LED, wherein the measurement circuit includes a controller, and the controller turns off the switch during normal operation and turns on the switch when an error occurs.

2. The two-wire transmitter according to claim 1, wherein the controller controls a current flowing through the current output circuit so that the two-wire transmitter outputs a burnout signal when an error occurs.

3. The two-wire transmitter according to claim 1, wherein the measurement circuit further includes a sensor, and the controller controls 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 normal operation.

4. The two-wire transmitter according to claim 1, wherein the controller turns off the switch when an error that has occurred when an error occurs has been resolved.

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

6. The two-wire transmitter according to claim 1, wherein the measurement circuit further includes a display, and the controller turns on a backlight of the display when an error occurs.

7. The two-wire transmitter according to claim 1, wherein the controller is capable of controlling a current flowing through the current output circuit so that the two-wire transmitter outputs a burnout signal when an error occurs, and the controller turns off the switch when an error occurs when the burnout signal is output. ​

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